A COMPARISON OF THE
PEAK PHYSICAL WORK CAPACITY DURING ARM ERGOMETRY, FES CYCLING, AND TWO HYBRID
EXERCISE CONDITIONS
IN SPINAL CORD INJURED
Verellen, J.1,2, Kerby, B.1,
Olijnyk, B.1, Saab, S.1, Smith, G.1, Jeon, J.1,
Steadward, R.D.1, Vanlandewijck, Y.2, Andrews, B.J.3,
Wheeler, G.D.1
1The Steadward Centre, Faculty of Physical
Education and Recreation, W1-67, Van Vliet Centre, University of Alberta,
Edmonton, Alberta, Canada. T6G 2H9
2Faculty of Physical Education and
Physiotherapy, Catholic University of Leuven, Tervuursevest 101,
B-3001 Heverlee, Belgium
3.University of Oxford, England, and The Stoke
Mandeville Hospital, National Spinal Injuries Unit.
The purpose of this study was to compare a
newly developed functional electrical stimulation (FES) assisted rowing machine
(ROWSTIM) with arm ergometry (ACE), FES cycling (CFES LE), and hybrid cranking
and cycling (CFES LE + ACE). Five SCI participants (C7-T12) underwent a
progressive maximal peak oxygen assessment to ascertain peak physical work capacity
across 4 conditions. Three trials per exercise modality were completed to
examine peak physical work capacity and to establish reliability of
measurement. A one-way ANOVA with condition as the main factor showed peak
absolute and relative functional aerobic capacity and heart rate to be
significantly lower for CFES LE versus ACE, CFES LE + ACE and FES ROW measures
(p < 0.05). However there were no significant differences between both
hybrid exercise conditions or between hybrid exercise and arm ergometry.
Preliminary results suggest that the ROWSTIM is as effective as an exercise
device or training tool for SCI as FES cycling or hybrid cycling and cranking.
However, a larger sample size and further technological developments of the
ROWSTIM are needed to demonstrate the efficacy of rowing over upper extremity
exercise and hybrid cycling and cranking.
Interest in enhancing exercise opportunities
for persons with SCI has been mediated by evidence of increased risk for heart
disease in this population./1/ One possible solution to enhance physical
activity of persons with SCI is through functional electrical stimulation
(FES)-assisted exercise technology. Demonstrated fitness and health related
benefits of FES assisted exercise include 1) increased cardiac function, such
as oxygen uptake, cardiac output and myocardial function; 2) increased venous
return by activating the muscle pump below the lesion level; 3) (theoretically)
reduced risk for deep vein thrombosis; 4) increased bone mineral density; 5)
increased muscle area and joint range of motion; 6) increased muscle strength
and endurance; 7) improved pulmonary function; and 8) increased self esteem and
enjoyment of the social contact./2/ More recently research has been focused on
combining FES leg ergometry with voluntary arm ergometry, referred to as hybrid
exercise (HE). This theoretically augments the cardiovascular stress during
exercise and consequently increases cardiovascular training effects./3,4/ Most
commonly used in this hybrid approach is the addition of FES cycling to upper
arm ergometry. Several studies have already demonstrated increased oxygen
consumption levels and cardiovascular training effects during submaximal and
maximal work compared to upper or lower extremity exercise alone./3,5,6,7,8/
Others have focused on a new form of hybrid exercise, FES rowing./5/ An FES
assisted rowing machine (ROWSTM) was developed at the Robert Steadward Centre,
Edmonton, Alberta by Dr Garry Wheeler and associates, to examine the potential
for extending hybrid training opportunities for persons with SCI./4,9/ Studies
by Laskin (1993) and later by Wheeler et al. (in press) suggest that the peak
oxygen consumption measures achieved using the ROWSTIM I and II systems are
comparable or superior to those reported in literature for other hybrid
exercise systems. In addition, it has been demonstrated that up to 36 sessions
of progressive FES rowing produces significant changes in cardiovascular
fitness in spinal cord injured participants./5/ Such data are important since
the FES rowing device is a much less expensive option for training and is very
well tolerated and accepted by SCI participants who have used it (personal
communications during the Laskin et al. (1993), the Wheeler et al. (in press)
studies and this investigation).
The purpose of this study was therefore to
conduct a within subject comparison of peak physical work capacity as defined
by peak functional aerobic power (VO2 peak) across 4 different types
of exercise: arm crank ergometry (ACE), FES leg cycling (CFES LE), hybrid
cycling and arm cranking (CFES LE + ACE) and electrical stimulation assisted
rowing (FESROW).
5 participants, 4 with complete and 1 with
incomplete SCI underwent a progressive maximal peak oxygen assessment to
ascertain peak physical work capacity across 4 conditions. Conditions were arm
ergometry (ACE), FES cycling (CFES LE), FES cycling combined with arm ergometry
(CFES LE + ACE) and FES rowing (FESROW) with 3 maximal exercise trials per exercise
modality to establish reliability of measurement. Each test was preceded by a 2
minute rest. The protocols for each exercise modality were the following:
ACE: Participants were instructed to
crank an arm crank ergometer (Monark Model 881, Varberg, Sweden) at 15 Watts
for 2 minutes. Every 2 minutes thereafter, power output was increased by 15
Watts until voluntary fatigue. Peak functional aerobic power was defined as VO2
at the point of failure to maintain 50 rpm arm cranking for at least 15 seconds
or until the participants voluntarily stopped cranking.
CFES LE: CFES LE was performed on the ERGYS
II cycle ergometer. The test protocol consisted of a 5 minute warm up with assisted pedalling. Participants were then
instructed to cycle at 0 Watts for 2 minutes. Every 2 minutes thereafter cycle
load was increased by 3 Watts. Peak functional aerobic power was defined as VO2
at the point of failure to maintain 35 rpm at maximum stimulation.
CFES LE + ACE: The test protocol consisted of a combination of the ACE and the CFES LE
protocol. Power output for cycling and cranking were increased every 2 minutes
with 3 and 15 Watts respectively in a way that participants were both cycling
and cranking simultaneously at their maximum as defined by their previous isolated
ACE and CFES LE tests until fatigue. Peak functional aerobic power was defined
as VO2 at the point of failure to maintain 35 rpm cycling at maximum
stimulation, failure to maintain 50 rpm cranking or until the participants
voluntarily stopped cranking.
FESROW: Participants were instructed to
start arm rowing at a heart rate equivalent to 40 % of their ACE functional
maximum aerobic capacity. After 2 minutes, participants started arm rowing with
assisted passive leg rowing at 50 % of their VO2 max for 2 minutes.
Thereafter, participants rowed (with leg stimulation) for 2 minutes at 60 % of
their VO2 max. After a 1 minute resting period, participants rowed
for 2 minutes at 80% of their VO2 max, and after another 1 minute
resting period participants were instructed to row at their maximum until
fatigue as defined by collapsing legs during the pull phase /5/ or if the
subjects reached exhaustion.
VO2 peak and HR were significantly
lower for CFES LE versus ACE, CFES LE + ACE and FES ROW measures (all p <
0.05). VO2 peak was consistently lower for ACE across all trials
versus CFES LE + ACE and FESROW, but the reported differences were not
significant (p>0.05). (Table
1)
|
|
ACE |
CFES
LE |
ACE +
CFES LE |
FESROW |
|
VO2 (l/min) |
1.72 |
1.02 |
2.03 |
2.06 |
|
VO2 (ml/min/kg) |
20.47 |
12.23 |
24.28 |
23.79 |
|
HR (bpm) |
160 |
103 |
161 |
162 |
Table 1: Mean peak absolute (l/min) and relative (ml/min/kg) VO2,
and HR (bpm) during ACE, CFES LE, CFES LE + ACE and FESROW
The need to develop exercise opportunities for
persons with SCI has already been demonstrated. Ashley et al. (1993) previously suggested the ROWSTIM may be
an alternative exercise solution for persons with SCI. Wheeler et al. (in press) demonstrated a 11.2 % increase in
peak O2 consumption after a 3 month progressive rowing training
program. However, the only available comparison with other electrical
stimulation (ES) assisted exercise modes to date was through literature data.
Clearly the next step in the development of the ROWSTIM was to conduct a within
subject comparison to determine peak work output from 4 different exercise
modalities.
Interestingly, the data indicate
how limited the potential CV training effect of cycling is. In agreement with
the findings of previous studies, data show that values for hybrid training are
significantly higher in comparison with the values of cycling only and clearly suggest that hybrid
exercise is superior to simple leg exercise./6,10/ In addition, Hooker (1992)
and Laskin (1993) demonstrated a significant difference of hybrid exercise over
ACE.
ES assisted and hybrid exercise has already
been associated with a number of physiological and psychological benefits.
However, additional benefits of FES rowing in terms of client appreciation have
also been reported. All participants preferred FES rowing over hybrid cycling
and cranking as rowing was considered to be a more natural movement. In
addition, since rowing utilises the shoulder retractors and muscles of lower
and upper back and forearms, this exercise could have additional benefits
reducing the risk of overuse and other wheelchair use related shoulder
problems./5/ As well, the ROWSTIM is a minimally adapted version of an exercise
tool for able-bodied people and is therefore easier and cheaper to manufacture.
However, there remain a number of
considerations that have to be taken into account. Only a small sample size was
used, reducing the statistical power of this investigation. Clearly a larger
sample size is necessary to further demonstrate the superiority of hybrid
rowing over upper extremity exercise and other hybrid training modalities. In
addition, there’s a number of modifications to the ROWSTIM that have to be
considered. Regarding electrode placement, an attempt was made to stimulate the
common peroneal nerve to facilitate the forward movement during the return
phase. The authors suggest that by stimulating the common peroneal nerve a less
powerful spring could be used, increasing the muscle work during training. As
well, power output during rowing can not be controlled. Clearly a controllable
power output would facilitate comparing hybrid and other training modalities in
terms of mechanical efficiency. However, the authors suggest that with further
technological developments, rowing represents a better hybrid training activity
than ACE or CFES LE + ACE. A brake that would sufficiently prevent the legs
from collapsing during the arm pull phase would neutralise the forward momentum
originated in this phase. Consequently, leg fatigue would be delayed and
exercise time and arm power output would further increase peak functional
aerobic capacity. As well, a combination of hybrid exercise and upper extremity
exercise alone would allow new participants to continue training while the legs
are recovering. As a consequence of these technological developments, an
increased arm power output and therefore a further increase in VO2 peak
by neutralising the forward momentum during the pull phase, can be expected.
Previous studies have already demonstrated the safety and efficacy of the ROWSTIM II system and suggested that this device represents a great potential for cardiovascular training for persons with SCI. This study clearly demonstrated that the aerobic demand during hybrid exercise and ACE were significantly higher than elicited during electrical stimulation assisted cycling. However, no significant differences were found between both hybrid exercise modalities and ACE. Further technological developments to the ROWSTIM II system are now necessary to further increase the metabolic demand during rowing. At present the team is working on a new break that would allow persons to train longer by minimising the force necessary to control for the forward momentum generated in the legs during the pull phase. In addition, we are confident that this break will also allow persons to train at a higher power output.
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The authors wish to acknowledge the Alberta
Heritage Foundation for Medical Research for providing a Phase I technology
commercialisation grant in support of this investigation.
Joeri Verellen
Katersberg 25
2440 Geel, Belgium
joeriverellen@hotmail.com