Electrical Stimulation In Walking

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ELECTRICAL STIMULATION IN WALKING

Abraham L.D., Marks W.B., and Loeb G.E. (1985) The distal hindlimb musculature of the cat. Cutaneous reflexes during locomotion. Exp. Brain Res. 58, 594-603.
Abstract: In order to better understand the organization of the locomotor control system, we examined the temporal patterns of distal hindlimb muscle responses to brief electrical stimulation of cutaneous nerves during walking on a treadmill. Electromyographic recordings were made from twelve muscles; stimuli were applied individually to three nerves at random times throughout the step cycle. A new graphical technique was developed to assist detailed examination of the time course and gating of complex reflex patterns. The short latency reflexes were of two primary types: inhibition of extensors and excitation of flexors; these responses were only evident during locomotor phases in which the respective motoneuron pools were active. Longer-latency response components were gated in a similar but not identical manner, suggesting some independence from the basic locomotory influence on the motoneuronal pool. The phase-dependent gating of reflexes appeared to be consistent with a functional role for reflex responses during locomotion. The reflex responses of muscles with complex anatomical actions were often correspondingly complex

Alway S.E., Hughson R.L., Green H.J., Patla A.E., and Frank J.S. (1987) Contractile properties of the human triceps surae following prolonged exercise and beta-blockade. Clin. Physiol 7, 151-163.
Abstract: Sixteen healthy males volunteered to perform both an incremental maximal and prolonged submaximal treadmill test with beta-blockade (2 X 80 mg oral propranolol per day) or matched placebo in a blind crossover design. Prior to and following the prolonged exercise, electrical stimulation of the triceps surae was performed to examine contractile properties. During the maximal test, the heart rate (HR) was reduced at all times by beta-blockade. The time to exhaustion in this test was significantly reduced by beta-blockade (P less than 0.03), while the maximal oxygen uptake (VO2 max) was not significantly lower (P = 0.06). In response to prolonged treadmill walking at 60% of VO2 max, the HR was reduced but VO2, respiratory quotient and ventilation were not affected by beta-blockade relative to placebo. Plasma concentrations of free fatty acids increased during exercise in the placebo but not beta- blocked treatment (P less than 0.0001). Plasma noradrenalin and adrenalin increased with exercise; the increase in adrenalin with beta- blockade was greater than that with placebo (P less than 0.0001). The RPE obtained at intervals during the prolonged exercise were greater for beta-blockades than placebo. Eight of 16 subjects were unable to complete full 90 min with beta-blockade; but all 16 completed the test with placebo. The electrically evoked twitches in the triceps surae muscle group after exercise did not differ in peak torque or one-half relaxation time compared to pre-exercise. The time to peak twitch torque was significantly shorter after exercise. No differences in twitch were observed due to beta-blockade. The tetanic responses at 10, 20, 50 and 100 Hz were not affected by either exercise or the beta- blockade. In conclusion, an increased subjective estimate of fatigue (RPE) was observed during prolonged exercise with beta-blockade. This subjective fatigue did not relate to altered peripheral muscle force production during electrical stimulation. The results suggest either a central rather than peripheral origin of fatigue, or fatigue in a muscle group not examined by stimulation of the triceps surae

Andersen J.B. and Sinkjaer T. (1999) The stretch reflex and H-reflex of the human soleus muscle during walking. Motor Control 3, 151-157.
Abstract: Due to the complexity of applying a well-defined stretch during human walking, most of our knowledge about the short latency stretch reflex modulation in humans is based on H-reflex studies. To illuminate the difference between the two methodologies, both types of reflexes were evoked in the same subjects, same experiment. Stretch reflexes were evoked via a stretch device capable of evoking stretch reflexes of the human soleus muscles during walking. H-reflexes were elicited by an electrical stimulation of the tibial nerve at the popliteal fossa at the knee. A significantly different modulation of the two reflexes was found in the late stance where the stretch reflex decreased in relation to the H-reflex. This was consistent with the unloading of the muscle spindles during the push-off in the late stance, suggesting a complex alpha-gamma coactivation, if any, at this time of the step. The soleus stretch reflex and H-reflex were compared during the stance phase of walking and sitting at matched soleus activity. No difference was found in the amplitude of the stretch reflex. However, there was a significant decrease of the H-reflex during the stance phase of walking, consistent with a task-specific presynaptic mediated reflex control. It is proposed that the short latency stretch reflex during walking is not sensitive to such a presynaptic inhibition

Angel A. and Clarke K.A. (1975) An analysis of the representation of the forelimb in the ventrobasal thalamic complex of the albino rat. J. Physiol 249, 399-423.
Abstract: 1. Glass micro-electrodes have been used to record from a total of 998 units situated in the ventrobasal thalamic complex in the deeply anaesthetized albino rat. 2. Of these units 889 responded to electrical stimulation of the contralateral forelimb and fifty-one to the contralateral hind limb. The remaining units consisted of those with receptive fields on the trunk, head and those which responded to stimulation of more than one limb. Only the latter group of units showed any spontaneous activity in the absence of intentional stimulation. 2. Of the units which responded to electrical stimulation of the contralateral forelimb the receptive fields, modality and latencies of response were accurately determined for 505 units. The mean latency to supramaximal stimulation at the wrist was 4.49 (+/- 0.04 S.E. of mean) msec; and to mechanical stimulation (for 146 of these units) at the centre of the receptive field 6.58 (+/- 0.12) msec. The modalities were distributed as follows: light pressure, 391; heavy pressure, 47; hair movement, 40; claw sensitive, 15 and joint movement, 12 units. 4. The forelimb representation within the ventrobasal thalamic complex was somatotopically organized, the over-all appearance being that of an incompletely closed fist, palmar surface uppermost, thumb media, with the wrist caudal and the digital tips rostral and dorsal. 5. The central projection was distorted, some parts showing expanded representation, notably the tips of digits II and III and the medial wrist pad. Other parts were contracted, e.g. the wrist, forearm and shoulder. 6. Units with receptive fields consisting of the whole of a walking pad had shorter mean latencies, to tactile stimulation, than those whose field was a single spot on a pad. 7. Units were found to show an abolute unresponsive time to the second of a pair of identical supramaximal electrical stimuli of up to 50 msec, and a relative unresponsive time which could last up to 500 msec. The absolute unresponsive and relative unresponsive times to the second of a pair of tactile stimuli was shorter being 30 and 150 msec respectively. 8. The effect of decortication was to increase the excitability of thalamic units to peripheral stimulation both in the initial and later discharges

Aniss A.M., Gandevia S.C., and Burke D. (1992) Reflex responses in active muscles elicited by stimulation of low- threshold afferents from the human foot. J. Neurophysiol. 67, 1375-1384.
Abstract: 1. Reflex responses were elicited in muscles that act at the ankle by electrical stimulation of low-threshold afferents from the foot in human subjects who were reclining supine. During steady voluntary contractions, stimulus trains (5 pulses at 300 Hz) were delivered at two intensities to the sural nerve (1.2-4.0 times sensory threshold) or to the posterior tibial nerve (1.1-3.0 times motor threshold for the intrinsic muscles of the foot). Electromyographic (EMG) recordings were made from tibialis anterior (TA), peroneus longus (PL), soleus (SOL), medial gastrocnemius (MG), and lateral gastrocnemius (LG) muscles by the use of intramuscular wire electrodes. 2. As assessed by averages of rectified EMG, stimulation of the sural or posterior tibial nerves at nonpainful levels evoked a complex oscillation with onset latencies as early as 40 ms and lasting up to 200 ms in each muscle. The most common initial responses in TA were a decrease in EMG activity at an onset latency of 54 ms for sural stimuli, and an increase at an onset latency of 49 ms for posterior tibial stimuli. The response of PL to stimulation of the two nerves began with a strong facilitation of 44 ms (sural) and 49 ms (posterior tibial). With SOL, stimulation of both nerves produced early inhibition beginning at 45 and 50 ms, respectively. With both LG and MG, sural stimuli produced an early facilitation at 52-53 ms. However, posterior tibial stimuli produced different initial responses in these two muscles: facilitation in LG at 50 ms and inhibition in MG at 51 ms. 3. Perstimulus time histograms of the discharge of 61 single motor units revealed generally similar reflex responses as in multiunit EMG. However, different reflex components were not equally apparent in the responses of different single motor units: an individual motor unit could respond slightly differently with a change in stimulus intensity or background contraction level. The multiunit EMG record represents a global average that does not necessarily depict the precise pattern of all motor units contributing to the average. 4. When subjects stood erect without support and with eyes closed, reflex patterns were seen only in active muscles, and the patterns were similar to those in the reclining posture. 5. It is concluded that afferents from mechanoreceptors in the sole of the foot have multisynaptic reflex connections with the motoneuron pools innervating the muscles that act at the ankle. When the muscles are active in standing or walking, cutaneous feedback may play a role in modulating motoneuron output and thereby contribute to stabilization of stance and gait

Apps R. and Lee S. (1999) Gating of transmission in climbing fibre paths to cerebellar cortical C1 and C3 zones in the rostral paramedian lobule during locomotion in the cat. J. Physiol 516 ( Pt 3), 875-883.
Abstract: 1. Climbing fibre field potentials evoked by low intensity (non- noxious) electrical stimulation of the ipsilateral superficial radial nerve have been recorded in the rostral paramedian lobule (PML) in awake cats. Chronically implanted microwires were used to monitor the responses at eight different C1 and C3 zone sites during quiet rest and during steady walking on a moving belt. The latency and other characteristics of the responses identified them as mediated mainly via the dorsal funiculus-spino-olivocerebellar path (DF-SOCP). 2. At each site, mean size of response (measured as the area under the field, in mV ms) varied systematically during the step cycle without parallel fluctuations in size of the peripheral nerve volley. Largest responses occurred overwhelmingly during the stance phase of the step cycle in the ipsilateral forelimb while smallest responses occurred most frequently during swing. 3. Simultaneous recording from pairs of C1 zone sites located in the anterior lobe (lobule V) and C1 or C3 zone sites in rostral PML revealed markedly different patterns of step- related modulation. 4. The findings shed light on the extent to which the SOCPs projecting to different parts of a given zone can be regarded as functionally uniform and have implications as to their reliability as channels for conveying peripheral signals to the cerebellum during locomotion

Armstrong D.M. and Drew T. (1984) Locomotor-related neuronal discharges in cat motor cortex compared with peripheral receptive fields and evoked movements. J. Physiol 346, 497-517.
Abstract: Discharge patterns of motor cortical neurones in cats walking steadily on a moving belt have been compared with other functional characteristics of the neurones. In forelimb motor cortex rhythmic discharges occurred in cells with peripheral receptive fields in all parts of the contralateral forelimb and also in cells with no discernible receptive field. Cells discharging at similar times during the step cycle often had very different receptive fields and cells with similar receptive fields (including neighbouring cells) could discharge at similar or at quite different times. In cells with a cutaneous receptive field including the forefoot the discharges during locomotion remained rhythmic (and their phasing relative to the step cycle was unchanged) when the response to mechanical stimulation in the receptive field was temporarily much reduced or abolished by local anaesthesia of the skin. The proportion of neurones showing accelerated firing during different parts of the step cycle fluctuated more for antidromically identified pyramidal tract neurones (p.t.n.s) than for non-p.t.n.s and was highest during the second half of stance in the contralateral forelimb and lowest during swing. When the neurones were subdivided according to the movement evoked by threshold electrical stimulation through the micro-electrode, p.t.n.s and non-p.t.n.s recorded by electrodes evoking elbow flexion showed a wide variety of discharge patterns. For p.t.n.s the discharge rate reached an average of 69 impulses/s during late stance and declined to an average of 26 impulses/s during swing

Babic J., Karcnik T., and Bajd T. (2001) Stability analysis of four-point walking. Gait. Posture. 14, 56-60.
Abstract: The aim of the experiment reported here was to determine the static and dynamic stability of two-point stance phases when walking on hands and knees at different speeds. In addition, we defined the methods and predicted the consequences of including two-point stance phases into crutch assisted functional electrical stimulation (FES) walking. Crawling on hands and knees was performed at three speeds by five healthy male persons. With twelve joint-position markers placed on the subject, we determined two stability indices for every instant of gait. We analysed the peak values of these two indices during the two-point stance phases. The results indicate that we have to ensure the proper position of the centre of gravity to increase the speed of walking. To reach speeds, lower than 0.6 m/s, it is not necessary to include statically unstable phases. The shift of the centre of gravity towards and across the leading stability edge can result in getting into the dynamically unstable state. Considering the results we can effectively introduce two-point stance phases into crutch assisted FES walking and therefore increase the speed and energy effectiveness of walking

Bajd T., Kralj A., Turk R., Benko H., and Sega J. (1983) The use of a four-channel electrical stimulator as an ambulatory aid for paraplegic patients. Phys. Ther. 63, 1116-1120.
Abstract: This article reports the use of electrical stimulation to provide paraplegic patients with complete lesions of the spinal cord the ability to rise from sitting to standing, to maintain a standing position, and to walk with a reciprocal gait. Four channels of electrical stimulation are sufficient for synthesis of a simple reciprocal gait pattern in these patients. During the double-stance phase, knee extensor muscles of both knees are stimulated, providing sufficient support for the body. Only one knee extensor muscle group is excited during the single-stance phase. The swing phase of the contralateral lower extremity is accomplished by eliciting the synergistic flexor muscle response through electrical stimulation of afferent nerves. The transition from the double-stance phase to the swing phase is controlled by two hand switches used by the therapist or built into the handles of the walking frame or crutches for use by the patient

Bajd T., Andrews B.J., Kralj A., and Katakis J. (1985) Restoration of walking in patients with incomplete spinal cord injuries by use of surface electrical stimulation--preliminary results. Prosthet. Orthot. Int. 9, 109-111.
Abstract: A group of patients who are good candidates for the application of Functional Electrical Stimulation (FES) to restore reciprocal walking is described. They have incomplete lesions of the spinal cord. Because of the degree of preserved voluntary control, proprioception and sensation some of these patients can achieve crutch assisted walking by means of multichannel electrical stimulation. In a number of cases the patient has sufficient strength and voluntary control in the upper limbs and at least one leg to provide safe standing for short periods in forearm crutches. For these patients a two channel stimulator controlled by a handswitch was applied to achieve safe and practical crutch assisted walking in a relatively short period of time

Bajd T., Kralj A., Turk R., and Benko H. (1990) Symmetry of FES responses in the lower extremities of paraplegic patients. J. Biomed. Eng 12, 415-418.
Abstract: Due to natural or artificial obstacles, gait is a less automatic and periodic process than it would appear when studying normal walking on the level. Pre-programmed functional electrical stimulation (FES) sequences, therefore, do not appear to be a suitable approach to the control of multichannel electrical stimulators in the restoration of paraplegic walking. Walking in paraplegic subjects must be, to a large extent, under voluntary control. To lessen the burden of this control, the symmetry of walking can be taken into account. Symmetric motion of the legs requires symmetric FES actuation. Symmetry of FES responses was studied in a group of 10 paraplegic subjects who had all undergone the FES training program. Recruitment curve, fatigue index and twitch delay were assessed. An average 80% symmetry was found in all parameters measured, thus allowing a reduction of complexity of control approach for FES locomotor aids

Bajd T., Kralj A., and Zefran M. (1993) Unstable states in four-point walking. J. Biomed. Eng 15, 159-162.
Abstract: The presently utilized walking patterns in paraplegic subjects with complete spinal cord injury (SCI) are compared by the help of graphic representations. Improved four-point gait assisted by functional electrical stimulation (FES) and crutches is proposed by introducing unstable states into the walking sequence. The unstable states are defined as passive phases of walking where the centre of mass (COM) is gravity driven in the direction of progression. The unstable state is described by a simple inverted pendulum model. Kinematic measurements of the unstable state were performed in normal and paraplegic subjects

Bajd T., Stefancic M., Matjacic Z., Kralj A., Savrin R., Benko H., Karcnik T., and Obreza P. (1997) Improvement in step clearance via calf muscle stimulation. Med. Biol. Eng Comput. 35, 113-116.
Abstract: The aim is to study the influence of electrically stimulated calf muscles on the effectiveness of the swinging leg movement. The study is carried out with a group of patients with incomplete spinal cord injuries both under stationary conditions and during crutch-assisted walking. Before stimulation is applied to the ankle plantar flexors, the knee extensors are inactivated. In each cycle, after ankle plantar flexor stimulation, peroneal stimulation is started, triggering the flexion reflex. From a biomechanical point of view, functional electrical stimulation (FES) of the ankle plantar flexors results in increased ground clearance of the lower extremity. Additionally, the FES-assisted lifting of the heel results in the elimination of extensor tone and thus shortens the swing time

Bajd T., Kralj A., Stefancic M., and Lavrac N. (1999) Use of functional electrical stimulation in the lower extremities of incomplete spinal cord injured patients. Artif. Organs 23, 403-409.
Abstract: After a program of therapeutic electrical stimulation, 3 groups of incomplete spinal cord injured (SCI) patients were identified, those in whom an improvement of both voluntary and stimulated muscle force was observed, those with an increase in stimulation response only, and patients in whom no effect of electrical stimulation training could be recorded. As it is difficult to predict the outcome of the electrical stimulation rehabilitation process, a diagnostic procedure was developed to predict soon after accidents which incomplete SCI patients are candidates for permanent use of a functional electrical stimulation (FES) orthotic aid. The candidates for chronic use of FES are patients with weak ankle dorsiflexors and sufficiently strong knee extensors. These patients are equipped with a single channel peroneal stimulator augmenting dorsiflexion and knee and hip flexion in a total lower limb flexion response. By applying FES to the ankle plantar flexors, the swing phase of walking can be significantly shortened and faster walking obtained

Barbeau H., Norman K., Fung J., Visintin M., and Ladouceur M. (1998) Does neurorehabilitation play a role in the recovery of walking in neurological populations? Ann. N. Y. Acad. Sci. 860, 377-392.
Abstract: This review demonstrates that neurorehabilitation approaches, based on recent neuroscience findings, can enhance locomotor recovery after a spinal cord injury or stroke. Findings are presented from more than 20 clinical studies conducted by numerous research groups on the effect of locomotor training using either body weight support (BWS), functional electrical stimulation (FES), pharmacological approaches or a combination of them. Among the approaches, only BWS-assisted locomotor training has been demonstrated to have a greater effect than conventional or locomotor training alone. However, when study results were combined and weighted for the number of subjects, the results indicated that there is a gradient of effects from small changes with the immediate application of FES or BWS to larger changes when locomotor training is combined with FES or BWS or pharmacological approaches. The findings of these studies suggest that these neurorehabilitation approaches do play a role in the recovery of walking in subjects with spinal cord injury or stroke. Several factors contribute to the potential for recovery including the site, etiology, and chronicity of the injury, as well as the type, duration, and specificity of the intervention and whether interventions are combined. Furthermore, how these neurorehabilitation approaches may take advantage of the plasticity process following neurological lesion is also discussed

Beillot J., Carre F., Le Claire G., Thoumie P., Perruoin-Verbe B., Cormerais A., Courtillon A., Tanguy E., Nadeau G., Rochcongar P., and Dassonville J. (1996) Energy consumption of paraplegic locomotion using reciprocating gait orthosis. Eur. J. Appl. Physiol Occup. Physiol 73, 376-381.
Abstract: The energy cost of walking using a reciprocating gait orthosis (RGOII) with functional electrical stimulation (FES) was assessed in 14 patients with spastic complete paraplegia from six rehabilitation centres. Before and after training asing RGOII with FES, the subjects performed a progressive maximal test on an arm-crank ergometer to obtain their laboratory peak oxygen uptake (LVO2peak), heart rate (HR) and blood lactate concentration changes. At the end of the training session, oxygen uptake (VO2) was measured during a walking test with orthosis at different speeds (6 min steady state at 0.1 m.s-1, followed by 2-min stages at progressively increasing speeds up to exhaustion). Of the subjects 4 repeated this test using orthosis without FES. At a speed of 0.1 m.s-1, VO2 represented 47 (SD 23)% of LVO2peak, mean HR was 137 (SD 21) beats.min-1 and mean blood lactate concentration 2.4. (SD 1.4) mmol.l-1. Maximal speed ranged from 0.23 to 0.5 m.s-1. At maximal speed, VO2 was 91 (SD 18)% of LVO2peak, mean HR reached 96 (SD 7)% and mean blood lactate concentration only 52 (SD 19)% of the maximal values measured during the laboratory test. Walking without electrical stimulation induced an increase in HR but there was no difference in VO2 and blood lactate compared to walking with stimulation. The training period did not result in any improvement in maximal physiological data. We concluded that the free cadence walking speed with orthosis remains much lower than that of able-bodied people or wheelchair users. The metabolic cost at a given speed is much higher even if, using a stimulation device, the cardiovascular stress is reduced

Betz R., Boden B., Triolo R., Mesgarzadeh M., Gardner E., and Fife R. (1996) Effects of functional electrical stimulation on the joints of adolescents with spinal cord injury. Paraplegia 34, 127-136.
Abstract: Nineteen adolescent subjects with complete spinal cord injuries resulting in paraplegia or tetraplegia participated in a functional electrical stimulation (FES) program consisting of computerized, controlled exercise and/or weight bearing. The effects of stimulated exercise and standing/walking on the lower extremity joints were prospectively studied. Plain radiographs and MRIs were obtained prior to and following completion of the exercise and standing and walking stages. In addition, the joints of five subjects were studied with synovial biopsies, arthroscopy, and the analysis of serum and synovial fluid for a 550 000 dalton cartilage matrix glycoprotein (CMGP). Pre- exercise joint abnormalities secondary to the spinal cord injury improved following the stimulation program. None of the subjects developed Charcot joint changes. Upon standing with FES, one subject with poor hip coverage prior to participation developed hip subluxation which required surgical repair. No other detrimental clinical effects occurred in the lower extremity joints of subjects participating in an FES program over a 1-year period

Bevengut M., Libersat F., and Clarac F. (1986) Dual locomotor activity selectively controlled by f. Neurosci. Lett. 66, 323-327.
Abstract: The crab Carcinus maenas walks laterally; moreover, as soon as leg contact with the support is lost, it starts swimming. In free-moving animals, discharges from individual f

Biering-Sorensen F., Gregersen H., Hagen E., Haugland M., Keith M., Larsen C.F., Leicht B.P., Nielsen F.H., Rabischong E., and Sinkjaer T. (2000) [Improved function of the hand in persons with tetraplegia using electric stimulation via implanted electrodes]. Ugeskr. Laeger 162, 2195-2198.
Abstract: Functional Electrical Stimulation (FES) is a controlled use of electrical stimulation of muscle contractions to obtain function. FES is utilised today in the treatment of spinal cord injured individuals for diaphragmatic pacing, bladder and bowel management, ejaculation, walking and hand function, as well as conditioning. We present The Freehand System, which consists of implanted electrodes to arm and hand muscles. This system has now been implanted in the first two Nordic tetraplegics. Candidates are tetraplegics with C5-6 lesions. After implantation it may take 6-8 months before the tetraplegic person can expect to use The Freehand System completely in daily life. The tetraplegic individual can choose between two grasps. The Freehand System can for some few very physically disabled tetraplegics be a good aid to increase their level of activities of daily living and independence. Continued development in the coming years may broaden the indications with benefit for more individuals

Bijak M., Hofer C., Lanmuller H., Mayr W., Sauermann S., Unger E., and Kern H. (1999) Personal computer supported eight channel surface stimulator for paraplegic walking: first results. Artif. Organs 23, 424-427.
Abstract: Today functional electrical stimulation (FES) is used among other treatments to restore hand and arm function, to restore mobility of the lower extremities, for phrenic pacing, and in cardiomyoplasty. Common to all FES applications is that they require careful setup of stimulation parameters. To improve these tasks, personal computer (PC) based software for stimulation parameter evaluation and data acquisition was written. First, the described software was used to mobilize paraplegic patients in conjunction with an 12C bus controlled 8 channel surface stimulator. Electrodes were placed on each leg on the m. quadriceps and m. gluteus for hip and knee extension and the peroneal nerve to elicit flexion reflex. The fourth channel was used to correspond to subjects' individual needs. The stimulation patterns for standing up, walking, and sitting down easily could be set up and optimized by adjusting up to 128 stimulation parameters in a task- specific way

Bobet J. (1998) Can muscle models improve FES-assisted walking after spinal cord injury? J. Electromyogr. Kinesiol. 8, 125-132.
Abstract: Some persons with a spinal cord injury can use functional electrical stimulation (FES) to walk again, but many cannot, and for those that can the walking obtained is limited. This paper argues that muscle models can help improve FES systems, but only if these muscle models are enhanced. Part 1 reviews differences between muscle models for FES systems and those for "natural" movement; FES models emphasize limb angle, demand simplicity, exploit feedback, and grade force through recruitment rather than rate coding. Part 2 tells how FES systems have used muscle models. Those that do not use muscle models to control stimulation do not fare well, although two recent ones (rule-based control and neural-net control with feedback) may yet do so. Those that do use muscle models provide good control initially, but fare poorly as the muscle properties change. Part 3 lists important questions that muscle models must address: questions of goal, type of activation, spasticity, simulation, simplicity, and fatigue. If these features can be incorporated, models can improve both the design and control of FES systems

Bogataj U., Kljajic M., Gros N., Acimovic R., Malezic M. (1994) The rehabilitation of gait after stroke: a comparison between conventional therapy and multichannel functional electrical stimulation therapy. Proc RESNA, 373-375.

Bogataj U., Gros N., Kljajic M., Acimovic –Janezic R. (1997) Enhanced rehabilitation of gait after stroke: a case report of a therapeutic approach using multichannel functional electrical stimulation. IEEE Trans. Rehabil. Eng. 5, 221-232.

Bogey R.A., Perry J., Bontrager E.L., Gronley J.K. (2000) Comparison of across-subject EMG profiles using surface and multiple indwelling wire electrodes during gait. J Electromyogr Kinesiol 10:255-259.

Botte M.J., Waters R.L., Keenan M.A. (1988) Orthopaedic management of the stroke patient:  Part 1: Pathophysiology, limb deformity and patient evaluation. Orthop Rev 27, 637-647.

Botte M.J., Bruffey J.D., Copp S.N., Colwell  C.W. (2000) Surgical reconstruction of acquired spastic foot and ankle deformity. Foot Ankle Clin. 5, 381-416.

Borges G., Ferguson K., and Kobetic R. (1989) Development and operation of portable and laboratory electrical stimulation systems for walking in paraplegic subjects. IEEE Trans. Biomed. Eng 36, 798-801.
Abstract: Two new stimulation systems have been designed for use in functional neuromuscular stimulation of paralyzed people; one is portable and one is a nonportable laboratory system. Compared to previous systems, these have greatly enhanced capabilities, especially in terms of memory capacity, expandability, and user interface. They are extensively operator programmable. The laboratory stimulation system was designed to provide quick turnaround time for stimulation pattern or program changes while maintaining complete compatibility with the portable system. The lab system will also accomodate external closed-loop control

Bowden D.M., Galkin T., and Rosvold H.E. (1975) Primate drinking system as defined by electrical stimulation of the brain (ESB). Physiol Behav. 15, 103-111.
Abstract: Four rhesus monkeys were examined by ESB for drinking sites in structures that had been previously demonstrated to support drinking behavior. Three yielded a significantly greater proportion of drinking sites than expected from the earlier study, and one yielded significantly less. As the exploration proceeded, the proportion of sites yielding drinking greatly increased in the drinkers and decreased in the nondrinker, and the ratio of stimulus-bound to nonstimulus-bound drinking sites increased in the drinkers but decreased in the nondrinker. Orienting responses decreased in both drinker and nondrinker as exploration proceeded. Two sites that had reliably supported drinking in the restraint chair failed to do so when telestimulated in a free environment, but instead yielded turning, walking, and climbing behavior. The results suggest that ESB-elicited drinking is determined by stimulation of several overlapping neural systems. These probably include ascending dopaminergic and cholinergic systems which are relatively thirst specific, and a nonspecific, cholinergic component of the reticular activating system which triggers the animal to execute a prepotent response which is specific to a given animal with a given history of stimulation under particular enviromental constraints. The learning of stimulus bound drinking is proposed to have its neural locus within the system which mediates the prepotent response, rather than in a thirst system or general activation system

Brandell B.R. (1982) Development of a universal control unit for functional electrical stimulation (FES). Am. J. Phys. Med. 61, 279-301.
Abstract: In collaboration with the College of Engineering the author has developed a laboratory, or clinic, based, battery operated "universal" control system, designed to improve disabled gait in upper motor neuron disabilities, especially stroke, hemiplegia, and cerebral palsy, by applying several channels of FES (Functional Electrical Stimulation) to the lower limb muscles while the patient is walking. The timing of the FES pulses, which can be applied to as many as six of the patient's muscles, is determined by potentiometer controlled one-shot timers, which are triggered by any of three switches in the sole of either shoe. Combinations of inverters, flip flops, AND gates and OR gates in the externally connected logic circuits determine the sequence of delays and pulses applied to the patient's muscles. This paper describes and diagrams some of the logic circuits and as an example of the possible application of the concept of a "universal" control unit reports the modifications of gait induced in a hemiplegic, four year post-stroke, patient. The characteristics of this patient's gait with FES in comparison to its characteristics without FES are demonstrated with motion picture frames, EMG recordings and graphic tracings of her right knee and ankle joint positions. They include more symmetrical timing of her right and left stance and swing phases, increased dorsiflexion of her right ankle in the swing phase, followed by a more distinct heel strike, and improved flexion--extension sequences of the knee and ankle joints and an increased heel rise in the stance phase. The author concludes that the gait characteristics of some hemiplegic patients will improve as they become adapted over a period of weeks or months to a control logic, which lessens their functional limitations by the use of a properly timed and amplified sequence of FES pulses. He suggests that the FES control requirements for individual patients should be determined experimentally with a control system "universally" adaptable to a wide range of disabilities, and that these control parameters could then determine the design of portable units, which may be used on a long term basis. These units would include only the operational options needed to duplicate the gait corrections found to be practicable for each individual patient, by the testing procedure, through a universal logic unit as described in this paper

Brandell B.R. (1986) The study and correction of human gait by electrical stimulation. Am. Surg. 52, 257-263.
Abstract: To gain a better understanding of the functions that the calf and vastus muscles perform in the human walking gait the author systematically increased the contractions of these muscles separately and in combination by applying Functional Electrical Stimulation (FES) to them, during walking tests performed by a subject with nonpathological gait, and a patient with a hemiplegic gait. A four- channel stimulator was used with foot switch activated control systems, which accurately sequenced the FES pulses and timed them in relation to the footswitch contacts. In normal gait FES applied to the calf muscles in the first third of the stance phase induced knee extension, but when applied later in the stance phase it increased the amount of plantar flexion and knee flexion at the push off. Strengthened vastus muscle contraction increased the amount and duration of stance phase knee extension, and interacted with the calf FES to increase the amount of heel rise at the push off. In the hemiplegic gait calf FES resulted in some increased knee flexion and ankle plantar flexion after the opposite heel strike, but a persistent lower limb extensor synergy prevented knee flexion from occurring simultaneously with plantar flexion and a heel rise, while the hemiplegic limb was still weight bearing

Braun Z., Mizrahi J., Najenson T., and Graupe D. (1985) Activation of paraplegic patients by functional electrical stimulation: training and biomechanical evaluation. Scand. J. Rehabil. Med. Suppl 12, 93-101.
Abstract: A training method for the activation of the lower limb muscles of paraplegics by functional electrical stimulation (FES) for standing and walking is described. It consists of a daily program which does not interfere with the normal routine of the patient. The treatment of four patients, paralysed form 7 to 30 years, is described. In these patients, a good standing position was achieved by stimulating the quadriceps, sometimes supplemented by the gluteus maximus or medius muscles. Gait was obtained by activation of the flexion reflex in a single stimulation and by tilting the trunk. Difficulties during gait were encountered due to the strong adduction of the legs. No mechanical support was required for locking of the lower limb joints. However, to maintain the equilibrium of the body, external support such as parallel bars, walker or Canadian crutches were used. During treatment gait improved due to reduction of spasticity and better stability of the body. Biomechanical measurements of weight bearing on the legs indicated values ranging between 41 to 65% of the body weight. During gait, a steady improvement of velocity was noted, with a parallel decrease in stance and stride times

Brissot R., Gallien P., Le Bot M.P., Beaubras A., Laisne D., Beillot J., and Dassonville J. (2000) Clinical experience with functional electrical stimulation-assisted gait with Parastep in spinal cord-injured patients. Spine 25, 501-508.
Abstract: STUDY DESIGN: Clinical evaluation of the Parastep method, a six-channel transcutaneous functional electrical stimulation device, in spinal cord- injured patients. OBJECTIVES: To investigate the motor performances of this new technique regarding energy expenditure and to evaluate its advantages and limitations, especially in social activities involving ambulation. METHODS: This study was conducted in 15 thoracic spine- injured patients. The lesion was complete except in two patients. The gait ability and the functional use were judged clinically. Energy cost was evaluated from heart rate, peak oxygen uptake, and lactatemia. RESULTS: Thirteen patients completed the training (mean: 20 sessions) and achieved independent ambulation with a walker. The mean walking distance, without rest, was 52.8 +/- 69 m, and the mean speed was 0.15 +/- 0.14 m/sec. One patient with incomplete lesion, who had been nonambulatory for 8 months after the injury, became able to walk without functional electrical stimulation after five sessions. The follow-up was 40 +/- 11 months. Five patients pursued using functional electrical stimulation-assisted gait as a means of physical exercise but not for ambulation in social activities. The patients experienced marked psychological benefits, with positive changes in their way of life. In three subjects, a comparison of physiologic responses to exercise between a progressive arm ergometer test and a walking test with the Parastep (Sigmedics, Inc., Northfield, IL) at a speed of 0.1 m/sec was performed, showing that the heart rate, the peak oxygen uptake, and lactatemia during gait were close to those obtained at the end of the maximal test on the ergometer. CONCLUSIONS: In spite of its ease of operation and good cosmetic acceptance, the Parastep approach has very limited applications for mobility in daily life, because of its modest performance associated with high metabolic cost and cardiovascular strain. However, it can be proposed as a resource to keep physical and psychological fitness in patients with spinal cord injury

Buford J.A. and Smith J.L. (1993) Adaptive control for backward quadrupedal walking. III. Stumbling corrective reactions and cutaneous reflex sensitivity. J. Neurophysiol. 70, 1102-1114.
Abstract: 1. Four cats were trained to walk backward (BWD) and forward (FWD) on a motorized treadmill. Mechanical (taps) or electrical (pulses) stimuli were applied to the dorsal or ventral aspect of the hind paw during swing or stance. Hindlimb kinematic data, obtained by digitizing 16-mm high-speed film, were synchronized with computer-analyzed electromyograms (EMG) recorded from anterior biceps femoris (ABF), vastus lateralis (VL), lateral gastrocnemius (LG), tibialis anterior (TA), and semitendinosus (ST). Responses to taps and pulses, as well as the modulation in cutaneous reflex sensitivity to pulses, were described for both walking directions and stimulus locations. 2. After dorsal taps that obstructed FWD swing, the hindlimb initially drew back away from the obstacle with knee flexion and ST activation, ankle extension with TA suppression and LG activation, and hip extension with ABF facilitation. Next, the limb was raised over the obstacle with resumed TA activity and enhanced knee and ankle flexion, and then compensatory knee and ankle extension positioned the limb for the ensuing stance phase. 3. For ventral taps that obstructed BWD swing, the initial response also tended to draw the limb away from the obstacle with hip and ankle flexion and TA facilitation and reduced knee flexion with weak VL facilitation and suppression of ST activity. Next, ST activity resumed as knee and ankle flexion raised the limb over the obstacle, and then compensatory extension completed the swing phase for BWD walking. Thus the initial kinematic and EMG responses to obstacles were opposite for BWD versus FWD swing, and these responses were consistent with active avoidance of the obstacles. Responses during BWD walking were subtle, however, compared with those for FWD. 4. After nonobstructing taps (ventral FWD, dorsal BWD), ST and TA activation and knee and ankle flexion were coincident, demonstrating that the aforementioned differences in responses to obstructing obstacles were not simply location dependent. Regardless of the direction of walking or the location of stimulation, taps applied during stance had little immediate kinematic effect, but the subsequent swing phase was usually exaggerated, as if the response was programmed to avoid any lingering obstacle. 5. Electrical pulses did not elicit the full-blown responses typically evoked by taps. The sequencing in activation of ST and TA characteristic after laps was absent after pulses, and there were rarely dramatic kinematic responses to pulses like those easily elicited by taps. There were, in fact, few differences in responses to electrical stimulation for BWD versus FWD walking.(ABSTRACT TRUNCATED AT 400 WORDS)

Burridge J., Taylor P., Hagan S., and Swain I. (1997) Experience of clinical use of the Odstock dropped foot stimulator. Artif. Organs 21, 254-260.
Abstract: The Odstock dropped foot stimulator (ODFS) is a simple functional electrical stimulation (FES) device for the correction of dropped foot. Improved reliability, fine control of stimulation parameters, and careful application and follow-up have let to 86% compliance. Data on 56 patients (50 patients with hemiplegia, 5 patients with multiple sclerosis, and 1 patient with spinal cord injury) who have used the system for between 6 and 18 months are presented and show a statistically significant increase in walking speed with the stimulator at 3 months of 14% (p < 0.001); decreased effort of walking, measured as physiological cost index (PCI), of 37% (p < 0.001); and statistically significant improvement in functional mobility tests and questionnaires. No statistically significant carryover was seen although 3 patients had sufficient improvement in active ankle control and gait parameters to no longer need the stimulator. Six patients who used the stimulator all day every day had a problem with skin irritation, which we have not yet been able to solve. Two patients discontinued use after experiencing increased spasticity in the calf

Burridge J.H., Taylor P.N., Hagan S.A., Wood D.E., and Swain I.D. (1997) The effects of common peroneal stimulation on the effort and speed of walking: a randomized controlled trial with chronic hemiplegic patients.  Clin. Rehabil. 11, 201-210.
Abstract: OBJECTIVE: To measure the effect of the Odstock Dropped Foot Stimulator (ODFS), a common peroneal stimulator, on the effort and speed of walking. DESIGN: A randomized controlled trial. SUBJECTS: Hemiplegic patients who had suffered a single stroke at least six months prior to the start of the trial whose walking was impaired by a drop-foot. INTERVENTIONS: The treatment, functional electrical stimulation (FES) group, used the stimulator and received a course of physiotherapy; the control group received physiotherapy alone. MAIN OUTCOME MEASURES: Changes in walking speed measured over 10 m and the effort of walking measured by physiological cost index (PCI). RESULTS: Thirty-two subjects completed the trial, 16 in the FES group and 16 in the control group. Mean increase in walking speed between the beginning and end of the trial was 20.5% in the FES group (when the stimulator was used), and 5.2% in the control group. Improvement was also measured in PCI with a reduction of 24.9% in the FES group (when the stimulator was used) and 1% in the control group. No improvement in these parameters was measured in the FES group when the stimulator was not used. CONCLUSION: Walking was statistically significantly improved when the ODFS was worn but no 'carry-over' was measured. Physiotherapy alone, in this group of subjects with established stroke, did not improve walking

Burridge J.H., Ladouceur M. (2001) Clinical and Therapeutic Applications of Neuromuscular Stimulation: A Review of Current Use and Speculation into Future Developments. Neuromodulation 4:147-154. [See Stroke and Brain-Injury references for abstract.]

Campbell J.M., Ball J. (1978) Energetics of Walking in Cerebral Palsy.  In: Waters R., et al: Energetics Application to the Study and Management of Locomotor Disabilities. Ortho Clin No Am 9,351-377.

Campbell J.M., Meadows P.M., Waters R.L., Wederich C., Jordan C. (1992) Improvement in Hemiplegic Gait with Multichannel, Implanted Electrical Stimulation System. Proc 14^th International Conference of the IEEE EMGS Paris, France, 1366-1368.

Campbell J.M., Meadows P.M. (1992) Therapeutic FES:  From Rehabilitation to Neural Prosthetics. Assistive Technology 4, 4-18.

Carmick J. (1993) Clinical use of neuromuscular electrical stimulation for children with cerebral palsy, Part 1: Lower extremity. Phys. Ther. 73, 505-513.
Abstract: This report, part 1 of a two-part case report on the clinical use of neuromuscular electrical stimulation (NMES) for children with cerebral palsy, documents the functional changes that occurred with the application of NMES to the lower extremity of three male children, 1.6, 6.7, and 10 years of age, all with hemiplegia due to cerebral palsy. Neuromuscular electrical stimulation was used in conjunction with a dynamic-systems, task-oriented model of motor learning. The children tolerated NMES well and at times demonstrated carryover after the removal of NMES. The youngest child showed immediate change in the ability to walk and run symmetrically. The two older boys demonstrated significant improvement in locomotor efficiency in a short time, although they were of an age when this improvement was not expected. One boy's Physiological Cost Index (PCI) measurement (a measure of locomotor efficiency) improved fourfold, and the other boy's PCI measurement improved by a factor of two. The results show preliminary evidence for the usefulness of NMES as an adjunct to the physical therapy program for improving function in children with cerebral palsy

Cha K., Horch K.W., and Normann R.A. (1992) Mobility performance with a pixelized vision system. Vision Res. 32, 1367-1372.
Abstract: A visual prosthesis, based on electrical stimulation of the visual cortex, has been suggested as a means for partially restoring functional vision in the blind. The prosthesis would create a pixelized visual sense consisting of punctate spots of light (phosphenes). The present study investigated the feasibility of achieving visually-guided mobility with such a visual sense. Psychophysical experiments were conducted on normally sighted human subjects, who were required to walk through a maze which included a series of obstacles, while their visual input was restricted to information from a pixelized vision simulator. Walking speed and number of body contacts with obstacles and walls were measured as a function of pixel number, pixel spacing, object minification, and field of view. The results indicate that a 25 x 25 array of pixels distributed within the foveal visual area could provide useful visually guided mobility in environments not requiring a high degree of pattern recognition

Chan V.W., Nazarnia S., Kaszas Z., and Perlas A. (1999) The impact of saline flush of the epidural catheter on resolution of epidural anesthesia in volunteers: a dose-response study. Anesth. Analg. 89, 1006-1010.
Abstract: We evaluated the effect of 1, 20, and 40 mL of epidural saline flush on recovery from lidocaine epidural anesthesia. Eight volunteers were studied for three study periods, each separated by 72 h. The volume of saline was randomized, and a new catheter was inserted for each study period. A standardized dose of 20 mL of 2% plain lidocaine was injected for 10 min, followed by an epidural saline flush 30 min later. Sensory block was assessed by pinprick and transcutaneous electrical stimulation and motor block by a modified Bromage scale and isometric maximal force contraction. Times to void and ambulate independently before discharge were recorded. Peak plasma lidocaine concentrations and time to peak concentration were determined. Results from six volunteers showed that epidural saline, 40 mL, significantly altered anesthetic resolution, accelerating the time of complete sensory and motor block regression (P < 0.05). Median peak levels of sensory and motor block and times to void and ambulate were similar among treatment groups. Peak plasma lidocaine concentrations were similar in all treatment groups. Our data suggest that a 40-mL epidural saline injection 30 min after the induction facilitates regression of epidural lidocaine anesthesia, but a 20-mL bolus does not. Epidural saline injection does not affect vascular absorption of epidural lidocaine. IMPLICATIONS: Epidural catheter flushing with 40 mL of saline, after establishment of epidural lidocaine anesthesia, can facilitate sensory and motor block recovery. However, this does not affect vascular absorption of epidural lidocaine

Christensen L.O., Andersen J.B., Sinkjaer T., and Nielsen J. (2001) Transcranial magnetic stimulation and stretch reflexes in the tibialis anterior muscle during human walking. J. Physiol 531, 545-557.
Abstract: Stretch of the ankle dorsiflexors was applied at different times of the walking cycle in 17 human subjects. When the stretch was applied in the swing phase, only small and variable reflex responses were observed in the active tibialis anterior (TA) muscle. Two of the reflex responses that could be distinguished had latencies which were comparable with the early (M1) and late (M3)components of the three reflex responses (M1, M2 and M3) observed during tonic dorsiflexion in sitting subjects. In the stance phase a single very large response was consistently observed in the inactive TA muscle. The peak of this response had the same latency as the peak of M3, but in the majority of subjects the onset latency was shorter than that of M3. The TA reflex response in the stance phase was abolished by ischaemia of the lower leg at the same time as the soleus H-reflex, suggesting that large muscle afferents were involved in the generation of the response. Motor-evoked potentials (MEPs) elicited in the TA by transcranial magnetic stimulation (TMS) were strongly facilitated corresponding to the peak of the stretch response in the stance phase and the late reflex response in the swing phase. A similar facilitation was not observed corresponding to the earlier responses in the swing phase and the initial part of the response in stance. Prior stretch did not facilitate MEPs evoked by transcranial electrical stimulation in the swing phase of walking. However, in the stance phase MEPs elicited by strong electrical stimulation were facilitated by prior stretch to the same extent as the MEPs evoked by TMS. The large responses to stretch seen in the stance phase are consistent with the idea that stretch reflexes are mainly involved in securing the stability of the supporting leg during walking. It is suggested that a transcortical reflex pathway may be partly involved in the generation of the TA stretch responses during walking

Cikajlo I. and Bajd T. (2000) Use of telekinesthetic feedback in walking assisted by functional electrical stimulation. J. Med. Eng Technol. 24, 14-19.
Abstract: A telekinesthetic feedback implemented into functional electrical stimulation (FES) orthosis is described. Single channel FES is used to provoke ankle dorsiflexion during walking. FES is controlled manually by a special lever, built into the handle of the crutch. The angular position of the lever defines the intensity of stimulation and thus the magnitude of the ankle dorsiflexion. The measured joint angle provides the feedback information about the ankle joint position, which is presented to the user as a force feedback applied to the control lever. As the first step in the development of a complex micromechatronic device, a simulated testing environment was prepared. A computer model, comprising dynamic foot characteristics, as well as agonistic and antagonistic muscle groups, substitutes the ankle joint. The model also includes fatiguing of the electrically stimulated muscles. For experimental purposes an actuated control lever was built. The efficacy of the telekinesthetic feedback was evaluated in a group of six healthy persons

Clippinger F.W., Seaber A.V., McElhaney J.H., Harrelson J.M., and Maxwell G.M. (1982) Afferent sensory feedback for lower extremity prosthesis. Clin. Orthop. 202-206.
Abstract: Electrical stimulation has been applied to sciatic nerves of patients to achieve sensory feedback after lower limb amputation for periods of up to six years. Patients used the sensory feedback device daily. Pain, infection and electrode displacement have not been problems. The immediate postoperative benefits are that pain is minimized after amputation and stump healing is improved. Furthermore, the stimulus affords the patient increased confidence when walking due to renewed awareness of the center of gravity. Improved ability to function in the dark and when walking up and down stairways makes the application of sciatic nerve stimulation after amputation very rewarding

Coburn B. (1984) Paraplegic ambulation: a systems point of view. Int. Rehabil. Med. 6, 19-24.
Abstract: Neurophysiological systems preserved distal to a complete spinal lesion, and relevant to walking, are reviewed in the manner of an engineering control systems analysis. On that basis, an outline is given of theoretical concepts, current developments and future possibilities for neuromuscular electrical stimulation to provide paraplegic ambulation

Dai R., Stein R.B., Andrews B.J., James K.B., and Wieler M. (1996) Application of tilt sensors in functional electrical stimulation. IEEE Trans. Rehabil. Eng 4, 63-72.
Abstract: Tilt sensors, or inclinometers have been investigated for the control of Functional Electrical Stimulation (FES) to improve the gait of persons who had a stroke or incomplete spinal cord injury (SCI). Different types of tilt sensors were studied for their characteristics and their performance in measuring the angular displacement of leg segments during gait. Signal patterns of the lower leg with inertial tilt sensors were identified with control subjects and subjects with footdrop who are being stimulated during level walking. To minimize acceleration responses when the foot swings or hits the ground, we use low-pass filtering (1.5-2 Hz). A finite state approach allows the sensor fixed on the shank to effectively detect the step intention in a population of stroke and incomplete SCI subjects and to control the FES. When the lower leg tilts backward, the common peroneal nerve is stimulated to bring the foot up and forward. We have designed a miniature footdrop stimulator with a magnetoresistive tilt sensor built in, so no external sensor cables are required. The thresholds to turn the stimulator on and off can be adjusted, as well as the maximum period of stimulation and the minimum interval between periods of stimulation. This device features several important advantages over traditional AFO's or stimulators controlled by foot switches. Initial trials with stroke and SCI subjects have demonstrated substantial gait improvement for some subjects, while most liked the good cosmesis and ease of using the device with a tilt sensor

Dalsing M.C., Zukowski A.J., Unthank J.L., Lalka S.G., Sawchuk A.P., and Cikrit D.F. (1994) Details of a canine venous insufficiency model. J. Invest Surg. 7, 85-93.
Abstract: Continued study of a chronic deep venous insufficiency (CDVI) model allows optimal comparison with the human condition. This study evaluates the model's long-term stability, its lack of observed clinical effect, and a simulated exercise study as a physiologic estimate of normal hindlimb walking. The time to maximal ankle venous pressure after standing (VFT), and to 90% of the venous refilling time after electrical stimulation, quadripedal, or hindlimb walking (VRT90), and the minimal pressure after exercise (AVP) were measured up to 10 months after CDVI model creation. The animals' intravenous resting pressure was obtained after standing stationary on all four limbs. Analysis of variance was used to determine statistical significance where indicated. VFT, AVP, and VRT90 measurements demonstrated values consistent with CDVI in animals studied up to 10 months after model creation and were statistically different from control limb values (p < or = .002, n = 8). Animals studied during quadripedal walking showed no difference in resting pressure, AVP, and VRT90 between model and control limbs (n = 5). There was no statistical difference in AVP or VRT90 measured under conditions of stimulated exercise or bipedal walking; and both conditions produced hemodynamic changes consistent with CDVI (n = 5). This animal model is a reliable long-term CDVI hemodynamic model. The normal venous hemodynamics recorded during quadripedic walking may explain the lack of clinical sequelae observed in this model. Lastly, the method of simulated exercise used in this study is a reliable test that reflects physiologic measurements obtained during bipedal walking

Davies C.T. and White M.J. (1982) Muscle weakness following dynamic exercise in humans. J. Appl. Physiol 53, 236-241.
Abstract: Electrical stimulation of the triceps surae in five healthy male subjects showed that following 1-2 h level running and uphill walking, at submaximal voltages of stimulation, exercise enhanced the twitch and tetanic responses, but the supramaximal time to peak tension (TPT), twitch (Pto) and tetanic tensions (Po) at 10 and 20 Hz were reduced by 16 ms (-12.6%), 11 (-8.9%), 163 (-17.5%), and 230 N (-18.1%), respectively. High-frequency (50 and 100 Hz) tetanic stimulation produced qualitatively similar changes to the 20-Hz response, but the stimulus response curve for the two frequencies was different and the ratio of 20- to 50-Hz response (20/50) (cf. Edwards et al., J. Physiol, London 272: 769-778, 1977) was voltage dependent. The reduction in Po at 100 Hz was associated with a decrease in maximal voluntary contraction (MVC). The effects of exercise on Pto and Po at 10, 20, 50, and 100 Hz were short lived and recovered within approximately 2 h. In contrast box-stepping produced a greater fall in Pto and Po at 10 and 20 Hz, which was long lasting (at least (22 h), and there was a consistent fall in the 20/50 ratio. a 2-min "fatigue" test showed that the muscles were weaker but not more fatigable after exercise. Our results seriously question the validity of using submaximal stimulation voltages and ratios for testing human muscle function and suggest that long-lasting muscle weakness is not associated with recovery from prolonged walking, running, and only observed after box-stepping exercise

de Castro M.C. and Cliquet A., Jr. (2000) Artificial sensorimotor integration in spinal cord injured subjects through neuromuscular and electrotactile stimulation. Artif. Organs 24, 710-717.
Abstract: Spinal cord injured (SCI) subjects lack sensorimotor functions. Neuromuscular electrical stimulation (NMES) systems have been used to artificially restore motor functions, but without proprioceptive feedback, SCI subjects can control NMES systems only when they can see their limbs. In a gait restoration system, the subject looks down to the ground to be aware of where his foot is while in a grasping activity, maximum grip strength is employed regardless of the force that is required to perform tasks. This report focuses on artificial sensorimotor integration. Multichannel stimulation was used to restore motor functions while encoded tactile sensation (moving fused phantom images) relating to artificially generated movements was provided by electrotactile stimulation during walking and grasping activities. The results showed that the sensorimotor integration attained yielded both the recognition of artificial grasp force patterns and a technique to be used by paraplegics allowing spatial awareness of their limb while walking

Debreceni L., Gyulai M., Debreceni A., and Szabo K. (1995) Results of transcutaneous electrical stimulation (TES) in cure of lower extremity arterial disease. Angiology 46, 613-618.
Abstract: The results of the treatment of 24 subjects--10 of them diabetic--with peripheral obstructive arterial disease of the lower limbs by transcutaneous electrical stimulation (TES) have been studied. The chronic ischemia of the lower extremities was complicated with ulceration in 12 and initial or advanced gangrene in 6 patients. All patients had been treated with antiplatelet drugs, pentoxifylline, and vasodilating drugs for many years. The drug therapy was continued, and TES was given daily for twenty minutes. The results were estimated after four to eight weeks of hospitalization and during a one-year follow-up in numerous cases. Except for 4 patients the improvement was very significant in all cases: the pain disappeared, the gangrenous process of the toes stopped, regression or complete healing of the ulceration could be observed, and the painfree walking distance increased. The oxygen saturation measured on the toes increased significantly during electrical stimulation. The blood pressure measured in the tibial artery showed very different changes. According to these observations TES appears to be a useful method superior to drug therapy in curing arterial circulatory disturbances of the lower extremities

DiMarco A.F., Romaniuk J.R., Von Euler C., and Yamamoto Y. (1983) Immediate changes in ventilation and respiratory pattern associated with onset and cessation of locomotion in the cat. J. Physiol 343, 1-16.
Abstract: In high decerebrate unanaesthetized cats (pre-collicular/pre-mamillary) which developed spontaneous co-ordinated locomotor activity, ventilation, breathing pattern, phrenic nerve, external and internal intercostal electromyogram (e.m.g.) activities were examined. Locomotion was also induced by electrical stimulation of the subthalamic locomotor region and in a few cases the mesencephalic locomotor region. Quadriceps muscle e.m.g. was used to monitor locomotor activity. Spontaneous locomotor activity was associated with an immediate increase in ventilation and shift of the ventilatory CO2 response curve to the left. Tidal volume was smaller and respiratory rate larger at any given level of ventilation during spontaneous locomotion. Increases in respiratory rate were due to reductions in both inspiratory and expiratory duration. Upon cessation of locomotion, these changes abruptly returned to control values. Within the first one or two walking steps of spontaneous locomotor activity, the rate of rise of phrenic activity increased slightly while peak phrenic activity remained relatively constant; peak internal intercostal activity increased markedly while peak external intercostal activity decreased. Similar changes in ventilation, phrenic, external and internal intercostal activities were observed in association with locomotion induced by stimulation within the subthalamic or mesencephalic locomotor regions. In contrast to spontaneous locomotor activity, however, increases in both external and internal intercostal activities were often observed. Peak amplitudes of both external and internal intercostal activities increased linearly with increasing levels of end- tidal PCO2 during rest and during locomotion. However, at any given level of PCO2 peak external intercostal activity was smaller and peak internal intercostal activity larger during locomotion than at rest. With increasing peak quadriceps e.m.g. activity at a constant walking rate, external intercostal activity was progressively inhibited while internal intercostal activity was progressively enhanced. No consistent change in peak phrenic activity was observed with changes in peak quadriceps activity. With increasing walking rate at a constant peak quadriceps e.m.g., peak phrenic and peak internal intercostal activities progressively increased and peak amplitude of external intercostal activity (which was inhibited below the activity observed at rest) also progressively increased. The virtually simultaneous changes in quadriceps activity and respiratory motor activities suggest that the increase in ventilation at exercise onset is neurally mediated. Furthermore, these results suggest that the motor pathways to both the spinal locomotor pattern generators and the pattern- controlling mechanisms for respiration are driven in parallel to provide a quantitative relationship between respiratory motor output and locomotor activity. The functional significance of the alterations in respiratory pattern and participation of the different respiratory muscles is discussed

Drew T. and Rossignol S. (1987) A kinematic and electromyographic study of cutaneous reflexes evoked from the forelimb of unrestrained walking cats. J. Neurophysiol. 57, 1160-1184.
Abstract: A kinematic and electromyographic (EMG) analysis was undertaken of the responses evoked in the forelimb of the cat by either mechanical obstruction of the forelimb during the swing phase of locomotion or by electrical stimulation of low-threshold cutaneous afferents during both swing and stance. Mechanical obstruction of the forelimb with a stiff metal rod evoked a complex response that allowed the cat to smoothly negotiate the obstacle without undue disruption of the overall locomotor rhythm. The initial movements were a flexion of the shoulder, together with a locking of the elbow joint, and a dorsiflexion of the wrist, which caused the limb to withdraw from the obstacle. They were followed by an extension of the shoulder, a flexion of the elbow, and a ventroflexion of the wrist, which together brought the limb forward and above the obstacle. The associated and complex pattern of s

Duenas S.H., Loeb G.E., and Marks W.B. (1990) Monosynaptic and dorsal root reflexes during locomotion in normal and thalamic cats. J. Neurophysiol. 63, 1467-1476.
Abstract: 1. In normal and thalamic walking cats electrical stimulation of muscle nerves via chronically implanted electrodes produced electromyographic (EMG) and neurographic responses that were modulated in amplitude depending on the phase of the step cycle. These responses were examined for possible indications of effects of primary afferent depolarization (PAD) during stepping. 2. Monosynaptic reflexes (MSRs) produced by stimulating the lateral gastrocnemius (LG) and medial gastrocnemius (MG) nerves were recorded as EMGs in MG or LG muscles during treadmill locomotion in normal cats. These heteronymous MSR responses were greatest during the stance (extensor) phase. 3. In the same animals, after decerebration, similar modulation of the heteronymous ankle extensor MSRs occurred during spontaneous locomotion with the use of the same stimulus and recording sites. 4. In both normal and thalamic cats the amplitude of neurogram responses recorded from LG or MG nerve after stimulation of the other muscle nerve varied with phase of stepping but did not parallel the variations of the MSR measured as EMG amplitude in the same muscle. The nerve responses were largest during the flexion phase of the step cycle and had a calculated central latency of 0.6-1.0 ms. These are interpreted as arising from antidromic activity in large-caliber afferent nerve fibers (i.e., dorsal root reflexes). 5. Spontaneous antidromic activity in severed L7 dorsal rootlet fibers to triceps surae was observed in the thalamic cats during episodes of locomotion and was closely correlated with flexion phase EMG activity in semitendinosus, a bifunctional muscle. 6. In decerebrate cats, dorsal root reflexes (DRRs) in severed filaments of L4-L7 dorsal roots were produced by stimulation of saphenous and posterior tibial nerves. These DRRs were always smaller during locomotion than during rest and were smallest during the flexion phase. 7. The short-latency antidromic activity produced in muscle nerves by stimulating heteronymous muscle nerves thus appears to be a DRR produced in Group I terminal arborizations that are depolarized close to threshold during the flexion phase. Such PAD could account for changes in the MSR that do not always parallel the levels of recruitment of the motor pools as manifest by background EMG amplitude

Duysens J., Tax A.A., Trippel M., and Dietz V. (1992) Phase-dependent reversal of reflexly induced movements during human gait. Exp. Brain Res. 90, 404-414.
Abstract: To investigate whether phase-dependent reversals in reflex responses on electromyography (EMG) are accompanied by movement reversals, a series of human volunteers were studied for their behavioural responses to sural nerve stimulation during running or walking on a treadmill. Low- intensity stimulation (less than 2.5 x perception threshold, T) of the sural nerve yielded facilitatory responses in the tibialis anterior muscle (TA), correlated with an induced ankle dorsiflexion (mean maximum 4 degrees) in early swing. The same stimuli yielded primarily TA suppression and weak ankle plantar flexion (mean maximum 1 degree) at end swing. The correlated induced knee angle changes did not precede the ankle changes, and they were relatively small. Mean maximum flexion in early swing was 6.2 degrees, while mean maximum extension was 3.7 degrees. High-intensity stimulation of the sural nerve (greater than 2.5 x T) always gave rise to suppression of the ongoing activity. This resulted in a second type of movement reversal. During late stance and early swing the responses in TA were suppressive (i.e. below background activity) and related to ankle plantar flexion. In contrast, the responses during early and middle stance consisted of suppression in extensor activity (gastrocnemius medialis and soleus) and ankle dorsiflexion. The data are discussed in terms of a new hypothesis, which states that the responses to electrical stimulation of cutaneous nerves during locomotion do not correspond directly to corrections for stumbling following mechanical perturbations during the step cycle. Instead, the data invite a reinterpretation in terms of the opening and closing of reflex pathways, presumably by a central pattern generator for locomotion

Edrich T., Riener R., and Quintern J. (2000) Analysis of passive elastic joint moments in paraplegics. IEEE Trans. Biomed. Eng 47, 1058-1065.
Abstract: In the functional electrical stimulation of the lower extremity of paraplegics to achieve standing and walking, a mathematical model describing the passive elastic joint moments is essential in order to implement model-based control algorithms. In a previous investigation of ten normal persons we had found significant coupling of passive, elastic joint moments between neighboring joints due to muscle groups that span both joints (biarticular muscles). Thus, we now investigated the biarticular coupling in six paraplegic patients. A comparison to the averaged results of the ten normal persons showed that while the biarticular joint moment coupling due to the gastrocnemius muscle was well preserved in all patients, the coupling due to the rectus femoris was greatly reduced and the coupling due to the hamstring muscle group was negligible. We offer pathophysiologically based explanations for these characteristic differences including the speculation that the predominantly extensor-type spasticity in our patients exercises mainly the anti-gravity muscles such as the gastrocnemius and the rectus femoris, while permitting greater atrophy of the hamstring muscle group. A previously presented double-exponential equation that predicts the joint moments under consideration of the neighboring joint angles could be fitted well to the experimental data

Edwards R.H., Chapman S.J., Newham D.J., and Jones D.A. (1987) Practical analysis of variability of muscle function measurements in Duchenne muscular dystrophy. Muscle Nerve 10, 6-14.
Abstract: To determine the possible sources of variation in performance indicators used in therapeutic trials, electrical stimulation techniques were used to measure contractile properties of the adductor pollicis and quadriceps muscles in boys with Duchenne muscular dystrophy. As no therapeutic effects were observed, longitudinal data obtained are taken to indicate changes in disease progress. Variance in voluntary contractions was found to be similar to that with electrically stimulated contractions; thus, variation could not be attributed to motivational changes, but rather to physiologic changes. Dystrophic muscle was slower to relax and less fatiguable than normal. However, such changes are of less significance to the overall disability compared to the loss of muscle bulk (cross-sectional area). Important variations in the function of individual muscles essential to complex performance, such as walking or getting up from the floor, could be masked by combining results from several muscle groups

Eichhorn K.F., Schubert W., and David E. (1984) Maintenance, training and functional use of denervated muscles. J. Biomed. Eng 6, 205-211.
Abstract: In the case of cerebral paralyses electrical stimulation can not only maintain the muscles, but may also enable their functional use. In flaccid paralyses, however, the conventional therapy using exponential currents produces rather unsatisfactory results. Only when applying bi- directional currents, were we successful in producing tetanic contractions. At present, some 20 children suffering from different diseases, such as spina bifida, Erb's palsy or a tumour of the cord, perform a daily domiciliary treatment with especially constructed home stimulators. Measurements prove distinct improvements of blood circulation, phosphoric metabolism and of the condition of the affected extremities. First investigations with computer-controlled, multi- channel devices show that by means of these devices the efficiency of training can be improved, the daily time for treatment can be shortened, and the disabled patient can perform the training almost autonomously. The existing experience on simple locomotion chains, and the achieved strengthening of the muscles will gradually enable a functional electrical stimulation of flaccid, denerved muscles and thus extend the radius of action for the disabled patient, for example by gripping, standing upright or walking

Eidelberg E., Walden J.G., and Nguyen L.H. (1981) Locomotor control in macaque monkeys. Brain 104, 647-663.
Abstract: We carried out experiments on young adult macaque monkeys (M.fascicularis) in an attempt to establish whether or not primates possess a locomotor control system consisting of spinal pattern generators modulated by brain-stem locomotor regions. We could not induce 'spinal stepping' in our subjects after spinal cord transection. Sparing of pathways contained in the central sector of the white matter of the cord was sufficient for stepping and walking. 'Controlled locomotion' was elicited in thalamic monkeys by electrical stimulation of the posterior subthalamic region or the midbrain tegmentum just ventral to the inferior colliculi. We conclude that there are significant homologies between this primate species and the cat regarding the probable existence of supraspinal locomotor control structures, but it seems that the presumed spinal step generators in monkeys depend more on supraspinal inputs than they do in cats

Endo Y., Tabata T., Kuroda H., Tadano T., Matsushima K., and Watanabe M. (1998) Induction of histidine decarboxylase in skeletal muscle in mice by electrical stimulation, prolonged walking and interleukin-1. J. Physiol 509 ( Pt 2), 587-598.
Abstract: 1. In normal non-exercised skeletal muscles in mice, the activity of histidine decarboxylase (HDC), the enzyme which forms histamine, was very low. 2. HDC activity in the quadriceps femoris muscle was markedly elevated following contractions evoked by even a few minutes of direct electrical stimulation, peaking at 8-12 h following contraction lasting 10 min, and gradually decreasing during the 24 h following contraction. The elevation in HDC activity depended on the duration and strength of stimulation. 3. Direct electrical stimulation induced a quantitatively similar elevation of HDC activity in the muscles of mast-cell-deficient mice (W/Wv mice). 4. Prolonged walking at a speed of 6 m min-1 for up to 6 h with a 30 min rest period at 3 h also elevated muscle HDC activity, the magnitude of the elevation being related to the duration of the walking. Repeated exercise (training) for several days diminished the elevation of muscle HDC activity induced by walking. In contrast, starvation augmented the elevation of muscle HDC activity induced by walking. 5. Intraperitoneal injection of interleukin-1beta (IL-1beta) also elevated muscle HDC activity in a dose-dependent manner, as little as 1 &mgr;g kg-1 of IL-1 producing a significant elevation of muscle HDC activity. 6. IL-1beta was immunohistochemically detected in normal non-exercised quadriceps femoris muscle. We could not detect a significant increase in IL-1beta after exercise in the muscle or in serum: it may be below the level of detection. 7. On the basis of these results, together with those reported previously and the known actions of histamine, we propose that an elevation of HDC activity and generation of histamine occur in skeletal muscle following muscle contraction possibly as a result of induction by IL-1beta and that the histamine may be involved in fatigue in skeletal muscle as part of a defence mechanism preventing damage to the muscle

Fedin A.N. (1980) [Certain functional connections of neurons control the walking of the cockroach Periplaneta americana]. Zh. Evol. Biokhim. Fiziol. 16, 454-460.
Abstract: On isolated abdominal nervous chain of the cockroach studies have been made of the responses of motoneurones of the thoracic ganglion to electrical stimulation of afferent axons of the leg nerve under normal conditions and during application of an anticholinesterase drug, GD-7. Depending on the type of stimulated axons, monosynaptic response, as well as polysynaptic phasic and tonic responses of motoneurones were recorded. A scheme of activation of motoneurones is suggested which evokes slow contractions of muscles in cockroach extremities

Ferguson K.A., Polando G., Kobetic R., Triolo R.J., and Marsolais E.B. (1999) Walking with a hybrid orthosis system. Spinal Cord. 37, 800-804.
Abstract: OBJECTIVE: The purpose of this case study was to determine the functional effectiveness of the hybrid orthosis system (HOS) for sit-to- stand and walking compared with the reciprocal gait orthosis (RGO) alone in a subject with significant orthopedic abnormalities. DESIGN: A subject with complete T7 paraplegia and a 13 cm leg length discrepancy was implanted with 14 intramuscular electrodes and fitted with a custom isocentric RGO. The subject was instructed in the use of the HOS and a two wheeled walker in the home and community settings. MAIN OUTCOME MEASURES: Using the Functional Independence Measure (FIM), and the Borg exertion scale the subject's level of independence and his perceived exertion was determined as well as the safety and efficacy of system use in the community. RESULTS: Results show that the HOS provided safe, independent ambulation with a two wheeled walker and met established criteria for limited community use. Walking in the RGO alone was feasible, however, the addition of functional electrical stimulation (FES) allowed this subject to walk farther and with less perceived exertion. CONCLUSION: This case study suggests that a hybrid orthosis system can be an effective clinical option for individuals with significant orthopedic complications that might otherwise contra- indicate the prescription of either conventional braces or FES alone

Field-Fote E.C. (2000) Spinal cord control of movement: implications for locomotor rehabilitation following spinal cord injury. Phys. Ther. 80, 477-484.
Abstract: In recent years, our understanding of the spinal cord's role in movement control has been greatly advanced. Research suggests that body weight support (BWS) walking and functional electrical stimulation (FES), techniques that are used by physical therapists, have potential to improve walking function in individuals with spinal cord injury (SCI), perhaps long after the stage of spontaneous recovery. Walking is one of the most desired goals of people with SCI; however, we are obligated to be judicious in our claims of locomotor recovery. There are few controlled studies that compare outcomes of BWS training or FES with those of conventional interventions, and access to services using BWS training or FES may be restricted under managed care

Fredriksen T.A., Bergmann S., Hesselberg J.P., Stolt-Nielsen A., Ringkjob R., and Sjaastad O. (1986) Electrical stimulation in multiple sclerosis. Comparison of transcutaneous electrical stimulation and epidural spinal cord stimulation. Appl. Neurophysiol. 49, 4-24.
Abstract: Forty-nine multiple sclerosis patients with bladder symptoms and/or walking disability were subjected to a therapeutic trial with electrical spinal cord stimulation and transcutaneous electrical stimulation, a second aim being to compare these two treatments. A clear subjective improvement in bladder symptoms was achieved in the majority of the cases, and this was substantiated by objective parameters. In a proportion of cases a more moderate improvement seems to have been achieved in a variety of symptoms. Transcutaneous electrical stimulation seems to be a useful selection procedure for later electrical spinal cord stimulation

Friedman R.N. and Si K. (1999) Initial characterization of the effects of Aloe vera at a crayfish neuromuscular junction. Phytother. Res. 13, 580-583.
Abstract: This study examines the effects of Aloe vera on neurotransmission processes in a well-established invertebrate neuromuscular junction preparation. We studied concentration-response relationships of an Aloe vera extract on excitatory junctional potentials (EJPs) at the opener muscle of the dactyl in the first and second walking limbs of crayfish (Procambarus clarkii and simulans). We observed concentration-dependent depolarizations of the muscle fibre membrane resting potential, depression of EJP amplitudes and an increase in latency to onset of the EJP following electrical stimulation of the isolated excitatory axon in the meropodite. These effects occurred with Aloe concentrations within the 1%-10% (wt-vol) range. Effects of lower concentrations, ranging to a minimum of 0.01% were equivocal. The effects of Aloe were at least partially, and in a majority of cases totally, reversible. EJPs reduced by Aloe could be restored by increasing the nerve stimulation amplitude. This, along with the latency increase, suggests a depression of action potential generation and conduction. The results provide a preliminary characterization of the effects of Aloe vera on the neurotransmission process and suggest that these effects may at least partially account for Aloe's analgesic and antiinflammatory effects. This study shows that the crayfish NMJ preparation should be useful for further elucidating the location(s) and mechanism(s) of action of Aloe on the nervous system

Fung J. and Barbeau H. (1994) Effects of conditioning cutaneomuscular stimulation on the soleus H- reflex in normal and spastic paretic subjects during walking and standing. J. Neurophysiol. 72, 2090-2104.
Abstract: 1. The modulation of the soleus H-reflex by a conditioning cutaneomuscular stimulation was investigated in 10 normal and 10 spastic paretic subjects who suffered from incomplete spinal cord lesions. The different motor tasks examined were standing, locomotion, and the maintenance of static limb postures to mimic critical gait events. The test soleus H-reflex was obtained by stimulating the tibial nerve in the popliteal fossa with a single 1-ms pulse at an intensity that produced a barely detectable M wave. The conditioning stimulus, consisting of an 11-ms train of three 1-ms pulses at 200 Hz, was delivered to the ipsilateral medial plantar arch, stimulating predominantly the medial plantar nerve, at an innocuous intensity of 2.5-3.0 X sensory threshold and at a conditioning-test delay of 45 ms. 2. During quiet standing, the H-reflex amplitude was inhibited only marginally by the conditioning cutaneomuscular stimulation, not reaching statistical significance in either the normal or spastic group of subjects. Although there was a trend of reflex inhibition in the normal subjects as the conditioning intensity was increased, a reversed trend of reflex facilitation was observed in the spastic patients. 3. During treadmill walking, the conditioned H-reflex was inhibited significantly during all phases in all the normal subjects and in one mildly impaired patient. In the moderately and severely impaired patients, cutaneomuscular stimulation selectively inhibited the soleus H-reflex in the early stance and swing phases, thereby producing a near normal phasic modulation pattern. Such modulatory effects were not present under static gait-mimicking conditions. 4. The task-specific and phase-dependent effects of cutaneomuscular stimulation on the soleus H-reflex in the spinal cord-injured patients revealed strong inhibitory influence on Ia afferents from cutaneomuscular inputs. It is plausible that inhibition occurs at both pre- and postsynaptic levels. 5. It is concluded that normal Ia modulatory mechanisms during locomotion are deficient in spastic spinal cord-injured patients and can partially and artificially be restored by cutaneomuscular stimulation applied to the sole of the foot. This can be used as a functional electrical stimulation (FES) regime in gait rehabilitation

Gallien P., Brissot R., Eyssette M., Tell L., Barat M., Wiart L., and Petit H. (1995) Restoration of gait by functional electrical stimulation for spinal cord injured patients. Paraplegia 33, 660-664.
Abstract: In this clinical study, we report the results of functional electrical stimulation for the ambulation of paraplegic patients without long leg braces (LLB), according to the Parastep approach. Of 13 SCI patients with complete neurological lesions included in this trial, 12 progressed to independent ambulation with the aid of the Parastep. The average walking distance was 76 m, with a maximum of 350 m, and the mean speed 0.2 m s-1. Compared to the situation with long leg braces, which in fact are given up by most paraplegic patients, long term home use seems to be much more important. Tolerance of this method is satisfactory. The psychological benefits of the device are remarkable. From this experience, it is concluded that this method is valuable for the restoration of standing and walking in the long term management of spinal cord injury patients

Garcia-Rill E., Skinner R.D., and Fitzgerald J.A. (1985) Chemical activation of the mesencephalic locomotor region. Brain Res. 330, 43-54.
Abstract: Electrical stimulation of the mesencephalic locomotor region (MLR) in the precollicular-postmammillary transected cat is known to induce controlled locomotion on a treadmill. We have been able to induce and block locomotion in this preparation by using localized infusions of transmitters and their agonists and antagonists. Infusions of the GABA antagonists bicuculline and picrotoxin into the MLR elicit locomotion at low concentration (5 mM). Applications of muscimol (5 mM) or GABA (0.5 M) were found to block chemically-induced locomotion, as well as electrically-elicited and spontaneous walking. Priming infusions of Diazepam amplified the blockage of locomotion by GABA. On the other hand, applications of strychnine (10 mM) were ineffective in inducing stepping, as were infusions of the excitatory agents glutamic acid, acetylcholine and norepinephrine. These findings suggest that the MLR is under inhibitory GABAergic input. The substantia nigra is the only known afferent to the MLR located posterior to the brainstem transection, and is a likely source for this input. A model is proposed to account for our results, as well as those of others, and it provides a working hypothesis for the neurochemical events occurring in brainstem centers which modulate locomotor events

Gaviria M. and Ohanna F. (1999) Variability of the fatigue response of paralyzed skeletal muscle in relation to the time after spinal cord injury: mechanical and electrophysiological characteristics. Eur. J. Appl. Physiol Occup. Physiol 80, 145-153.
Abstract: The aim of this study was to determine the effect of the time after spinal cord injury (less than and greater than 10 months) on the mechanical and electrophysiological characteristics of muscle fatigue of the paralyzed electrically stimulated quadriceps muscle. Morphologically and histochemically, a relationship was observed between muscle fatigue and the delay from injury, revealing a critical period of enzymatic turning and a maximum peak of atrophy around the 10th month after the injury, followed by a long-term stabilization. Knee-torque output and M-wave variables (amplitude, latency, duration, and root mean square, RMS) of two muscular heads of the quadriceps were recorded in 19 paraplegic patients during a 120-s isometric contraction. The fatiguing muscle contraction was elicited by supramaximal continuous 20-Hz electrical stimulation. Compared to the chronic group, the acutely paralyzed group showed a greater resistance to fatigue (amount and rate of force decline, P < or = 0.01), smaller alterations of the M-wave amplitude and RMS, and a limited decrease of the muscle fiber conduction velocity (P < 0.05). Mechanical and electrophysiological changes during fatigue provided a clear functional support of the transformation of skeletal muscle under the lesion and of the existence of a critical period of muscular turn. In conclusion, when considering the artificial restoration of motor function, the evolution of the endurance and force-generating capabilities of the muscle actuator must be taken into account, particularly when tasks require important safety conditions (e.g., standing and walking)

Godec C.J. and Cass A.S. (1980) Cystometric variations during postural changes and functional electrical stimulation of the pelvic floor muscles. J. Urol. 123, 722-725.
Abstract: Postural changes did not affect the cystometric curves of bladder function that were hyperreflexic, flaccid or secondary to bladder wall changes (fibrosis and inflammation). However, postural changes did affect normal curves in some patients with a history of micsturition disorders and resulted in detrusor instability when the patient was standing or walking. Functional electrical stimulation of the pelvic floor muscles during the cystometrogram inhibited detrusor instability of these patients in all positions. Use of postural changes and functional electrical stimulation of the pelvic floor muscles during the cystometrogram inhibited detrusor instability of these patients in all positions. Use of postural changes and functional electrical stimulation of the pelvic floor muscles is suggested to determine actual bladder function and to exclude possible artifacts in the curve

Granat M., Keating J.F., Smith A.C., Delargy M., and Andrews B.J. (1992) The use of functional electrical stimulation to assist gait in patients with incomplete spinal cord injury. Disabil. Rehabil. 14, 93-97.
Abstract: The use of FES (functional electrical stimulation) for gait reproduction in six patients with spinal cord injury is described. Following a detailed neuromuscular assessment the patients commenced a muscle conditioning programme using electrical stimulation applied via surface electrodes. Once patients were strong enough to stand, gait synthesis was initiated in the laboratory utilizing a programmable electrical stimulator. When a satisfactory gait pattern had been achieved, patients used their portable stimulator at home. All six patients became able to stand and walk using the FES system and completed the home phase of the programme. Three patients continue to use the system at home for exercise and walking; the other patients have discontinued using the system, preferring a wheelchair or their original orthoses. We conclude that FES-assisted walking is feasible in patients with incomplete spinal cord injury, even with severe motor loss. Further advances in technology are needed for the system to become applicable to a larger number of patients

Graupe D., Kohn K.H., Kralj A., and Basseas S. (1983) Patient controlled electrical stimulation via EMG signature discrimination for providing certain paraplegics with primitive walking functions. J. Biomed. Eng 5, 220-226.

Graupe D. and Kohn K.H. (1987) A critical review of EMG-controlled electrical stimulation in paraplegics. Crit Rev. Biomed. Eng 15, 187-210.
Abstract: This review presents a description and provides a comparative performance evaluation of EMG control vs. other approaches to controlling functional electrical stimulation (FES) in upper-motor- neuron paraplegics to provide them with a certain degree of walking ability with walker support. EMG control is considered in terms of a combination of above-lesion EMG control and below-lesion response-EMG control. The above-lesion EMG is to control the activation of different limb functions involved in standing up and walking via FES. This control is accomplished by analyzing raw surface EMG time-series patterns to discriminate between upper-trunk muscle contraction patterns which, in turn, are correlated with intended lower-limb functions involved in walking, so that natural and instinctive balance changes of paraplegics are reflected and controlled by the patient only above the lesion. The below-lesion response-EMG is the EMG produced in response to the FES pulses at the stimulation sites, for adjusting stimulation levels as needed when contractions weaken due to muscle fatigue. Above-lesion EMG is a stochastic (random-like) signal, being a response to unsynchronized motor-neuron firings, whereas the below- lesion EMG is a deterministic signal responding to synchronized firings that result solely from the FES pulses. The present review discusses the merits and difficulties of EMG control and attempts to give a critical evaluation of patient performance under such control, contrasted to other methods of control, noting that FES-activated walking without adequate and patient-responsive control is of very limited attraction and use to paraplegics. Of the various control methods, only

Graupe D., Kohn K.H., and Basseas S. (1988) A. J. Biomed. Eng 10, 305-311.
Abstract: We describe and evaluate a

Graupe D. (1989) EMG pattern analysis for patient-responsive control of FES in paraplegics for walker-supported walking. IEEE Trans. Biomed. Eng 36, 711-719.
Abstract: This paper describes and discusses the employment of EMG pattern analysis to provide upper-motor-neuron paraplegics with patient- responsive control of FES (functional electrical stimulation) for the purpose of walker-supported walking. The system described employs above- lesion surface EMG signals to activate standing and walking functions in a patient-responsive manner. This system has been experimentally applied to paraplegics at Michael Reese Hospital and Medical Center in Chicago since early 1982. Below-lesion response-EMG control from the stimulated sites has been added in 1987 to regulate stimuli levels in the face of fatigue. Although transcutaneous FES alone is being employed, the system is applicable in principle also to implantable FES systems

Graupe D. and Kordylewski H. (1995) Artificial neural network control of FES in paraplegics for patient responsive ambulation. IEEE Trans. Biomed. Eng 42, 699-707.
Abstract: This paper describes an ART-1-based artificial neural network (ANN) adapted for controlling functional electrical stimulation (FES) to facilitate patient-responsive ambulation by paralyzed patients with spinal cord injuries. This network is to serve as a controller in an FES system developed by the first author which is presently in use by 300 patients worldwide (still without ANN control) and which was the first and the only FES system approved by the FDA. The proposed neural network discriminates above-lesion upper-trunk electromyographic (EMG) time series to activate standing and walking functions under FES and controls FES stimuli levels using response-EMG signals. For this particular application, we introduce several modifications of the binary adaptive resonance theory (ART-1) for pattern recognition and classification. First, a modified on-line learning rule is proposed. The new rule assures bidirectional modification of the stored patterns and prevents noise interference. Second, a new reset rule is proposed which prevents "exact matching" when the input is a subset of the chosen pattern. We show the applicability of a single ART-1-based structure to solving two problems, namely, 1) signal pattern recognition and classification, and 2) control. This also facilitates ambulation of paraplegics under FES, with adequate patient interaction in initial system training, retraining the network when needed, and in allowing patient's manual override in the case of error, where any manual override serves as a retraining input to the neural network. Thus, the practical control problems (arising in actual independent patient ambulation via FES) were all satisfied by a relatively simple ANN design