The effects of functional electrically stimulated (FES)-arm ergometry on upper limb function and resting cardiovascular outcomes in individuals with tetraplegia: A pilot study

doi:10.4236/ojtr.2013.12004

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Vol.1, No.2, 17-21 (2013) Open Journal of Therapy and Rehabilitation

http://dx.doi.org/10.4236/ojtr.2013.12004

The effects of functional electrically stimulated

(FES)-arm ergometry on upper limb function and

resting cardiovascular outcomes in individuals

with tetraplegia: A pilot study

Jennifer Ptasinski, Hisham Sharif, David Ditor*

Department of Kinesiology, Brock University, St. Catharines, Canada; *Corresponding Author: [email protected]

Received 10 September 2013; revised 12 October 2013; accepted 19 October 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Background: Functional electrically stimulated

(FES)-arm ergometry has been shown to in-

crease peak power output and aerobic capacity

in individuals with cervical SCI. However, the

functional benefits remain unknown. Objective:

To determine the effects of FES-arm ergometry

on exercise performance, upper limb function

and resting cardiovascular function in individu-

als with tetraplegia. Methods: Five individuals

(43.8 ± 15.4 years old) with SCI (C3-C5, AIS C-D,

14.0 ± 1 1.1 years post-injury) completed 12 weeks

FES-arm ergometry. Exercise performance (time

and distance to fatigue), perceived upper limb

function [Capabilities of Upper Extremity Ques-

tionnaire (CUE), short form-Quadriplegia Index

of Function Questionnaire (sf-QIF) and Spinal

Cord Injury Spast icit y Ev a lu a t io n To o l ( SC I - SE T )]

and resting mean arterial pressure (MAP) and

heart rate (HR) were measured pre and post.

Results: Following training, MAP significantly

decreased (91.1 ± 14.0 to 87.7 ± 14.7 mmHg; p =

0.04), and there was a trend for an increased

time to fatigue (804.6 ± 359.4 to 1483.8 ± 1110.2

sec; p = 0.08), distance to fatigue (3508.4 ±

3524.5 to 7412.6 ± 7773.1 m, p = 0.08) and the

CUE scores pertaining to hand function (31.6 ±

12.8 to 38.0 ± 17.7; p = 0.07). Conclusion: Twel ve-

week FES-arm ergometry was associated with

decreased resting MAP in individuals with tetra-

plegia, and may show promise as a means to

increase exercise performance and hand func-

tion. Further research is required to verify these

preliminary findings.

Keywords: Exercise; Spinal Cord Injury; Exercise

Performance; Arm Function; Blood Pressure

1. INTRODUCTION

For individuals with cervical SCI, reductions in hand

and upper limb function can be particularly debilitating.

In a study conducted by Anderson, 681 individuals with

SCI were surveyed, and for those with tetraplegia, the

return of arm and hand function was ranked as the

highest therapeutic priority [1]. This is understandable as

recovery of even partial hand and arm function could po-

tentially have a great impact on independence. Anderson

also found that 96.5% of individuals with a SCI consi-

dered exercise to be important for functional recovery,

however, only 56.9% had access to exercise, and only

12.2% had access to a trained therapist. These findings

demonstrate a need for therapies which are targeted at

upper limb and hand musculature, and have the potential

to improve function and independence.

Manual arm ergometry has been shown to result in

physical improvements in individuals with SCI [2]. Un-

fortunately, the potential benefits attained from this form

of exercise are limited to those with at least partial upper

limb mobility. However, functional electrically stimula-

ted (FES) exercise is a therapeutic option for individuals

with SCI and FES-arm ergometry which has recently

become available. This form of exercise involves

electrical stimulation of the upper limb musculature,

which is in such a sequence as to cause a fluid arm-

cycling motion. A recent study found that 12 weeks of

thrice-weekly progressive FES-arm ergometry resulted in

increased peak power output and peak aerobic capacity

in individuals with cervical SCI [3]. Although these

results are very encouraging, the functional benefits of

J. Ptasinski et al. / Open Journal of Therapy and Rehabilitation 1 (2013) 17-21

FES-arm ergometry have yet to be fully determined.

Therefore, the purpose of the present study was to

investigate the effects of a 12-week, thrice-weekly, FES-

arm ergometry program on exercise performance, upper

limb function and resting cardiovascular outcomes in

individuals with chronic incomplete tetraplegia. We hy-

pothesized that 12 weeks of FES-arm ergometry would

improve participants’ exercise performance, upper limb

function and resting cardiovascular measures.

2. MATERIALS AND METHODS

2.1. Participants

Five individuals (4 male, 1 female; 43.8 ± 15.4 years

old) with chronic, incomplete SCI (C3-C5, AIS C-D,

14.0 ± 11.1 years post-injury) were recruited to partici-

pate in this study. Participant characteristics are detailed

in Table 1. All participants received medical approval

before enrolment into the study, and no participant had

undertaken FES-exercise training, or any other structured

exercise training, in the three months prior to the study.

Individuals were excluded from the study if they had do-

cumented cardiovascular disease, a tracheostomy, uncon-

trolled autonomic dysreflexia, or any other medical con-

dition contraindicating exercise. Participants were not re-

quired to discontinue their medications during the testing

or training sessions, and no participants made any change

in their medications during the course of training. This

study was approved by the Research Ethics Board of

Brock University and all participants provided informed

and signed consent before participating. All procedures

conformed with The Code Ethics of the World Medical

Association (Declaration of Helsinki) of July 1964.

2.2. Intervention

FES-arm ergometry was completed on the RT300 er-

gometer (Restorative Therapies; Baltimore, MD), with

surface electrodes (2 × 3.5 inch; PALS Platinum) being

placed on the biceps, triceps, medial deltoids, and supra-

spinatus muscles. For participants with inadequate grip

strength, tensor bandages were used to secure the hands

Table 1. Participant characteristics.

Participant Age Sex Level of Injury AIS Years Post Injury

1 26 Male C4 C 7

2 46 Male C5 C 20

3 30 Male C5 C 11

4 58 Female C3 D 30

5 59 Male C3 C 2

AIS: ASIA impairment scale, ASIA denotes American Spinal Injury Asso-

ciation.

to the grips of the RT300. The training protocol included

12 weeks of FES-arm cycling, at a frequency of three

sessions per week, with a minimum of 30 minutes and a

maximum of 45 minutes of active exercise per session.

There was 48 hours of rest between exercise sessions

whenever possible. The RT300 includes a motor that can

be used to assist the pedaling motion or provide resis-

tance as participants progress over time. Each exercise

session began with a two minute passive, motor-driven

warm up, followed by 30 - 45 minutes of active FES-arm

ergometry, and was completed with a two minute passive,

motor-driven cool down. The stimulation pulse width

was set at 250 µs, and the stimulation frequency was set

at 50 Hz for the biceps and triceps electrodes, and 25 Hz

for the deltoid and supraspinatus electrodes. The stimula-

tion current amplitude was adjustable between 0 to 140

mA, however, for the present study the current was set,

as individually tolerated by comfort, between 15 and 50

mA.

The exercise sessions were progressed as individually

tolerated by increasing the duration of exercise, followed

by increasing the resistance provided by the motor of the

arm ergometer. Specifically, each exercise session was to

include at least 30 minutes of active exercise, and no

more than 45 minutes of exercise. If the upper limbs fa-

tigued before 30 minutes, then a 5 minute rest period was

allowed and a subsequent bout would be performed. This

would continue until at least 30 minutes of exercise had

been accomplished. When a participant was able to per-

form two consecutive sessions of 30 minutes continuo-

usly, the resistance would be increased by one unit as

indicated on the RT300. The RT300 stimulates the mus-

cles such that a target cadence of 50 revolutions per mi-

nute is maintained, and fatigue was determined automa-

tically by the RT300 when, despite maximal stimulation,

the cadence of pedaling dropped below 35 revolutions

per minute for 2 seconds. Although no maximum ca-

dence was set, the revolutions per minute did not exceed

55.

A maximum of five bouts per session were allotted to

complete the 30 - 45 minutes of exercise per session.

Participants had to maintain an exercise adherence of at

least 75% for their data to be included in the analysis.

2.3. Outcome Measures

Exercise performance measures were collected via an

exercise to fatigue test. This test was conducted at base-

line and again following the completion of the 12-week

training program (48 hours following the final training

session), and the resistance used for each individual was

held constant for each test. These measures of perform-

ance included time to fatigue and distance to fatigue.

Functional outcomes included self-reported measures

of upper extremity function and independence as deter-

J. Ptasinski et al. / Open Journal of Therapy and Rehabilitation 1 (2013) 17-21 19

mined by the Capabilities of Upper Extremity Question-

naire (CUE) [4], and the short form of the Quadriplegia

Index of Function Questionnaire (sf-QIF) [5]. The CUE

is a 32-item questionnaire that evaluates how well an

individual can perform movements with his or her arms

and hands. The left and right limbs are scored separately

on a seven point scale with 1 = totally limited and 7 = not

at all limited. The sf-QIF is a 6-item questionnaire that

evaluates an individual’s level of independence when

performing activities of daily living that require upper

limb function. Items are rated on a 5-point scale with 0 =

dependent and 4 = independent.

Self-reported muscle spasticity was determined by the

Spinal Cord Injury Spasticity Evaluation Tool (SCI-SET)

[6]. This 35-item, 7-day recall questionnaire does not

evaluate the amount of spasticity per se, but rather, it

evaluates how spasticity affects (either positively or ne-

gatively), certain activities of daily living. The SCI-SET

questionnaire employs a 7-point scale with −3 = extre-

mely problematic, 0 = no effect, and 3 = extremely help-

ful. All functional outcome measures were made at base-

line and following the 12-week exercise training pro-

gram.

Resting mean arterial blood pressure (MAP) and heart

rate (HR) were conducted at baseline and following

twelve weeks of FES-arm ergometry exercise (48 hours

following the final training session). Resting cardiova-

scular measures were conducted in the supine position

following 10 minutes of rest in a dark, quiet room. MAP

and HR were determined via an automated cuff placed

over the left brachial artery, and measures were taken

twice per test and averaged to determine the true resting

value.

2.4. Statistical Analysis

All statistical analyses were conducted with the Statis-

tica software program. Due to the relatively small sample

size and high amount of baseline variability between par-

ticipants, outcome measures were compared pre and

post-testing with non-parametric statistical analysis. Spe-

cifically, the Wilcoxon test was used to compare means

at pre and post-testing. Effect size (ES) calculations were

also conducted on all outcome measures for the baseline

and 12-week values. Statistical significance was set at p

< 0.05, and all values are expressed as mean ± standard

deviation (SD).

3. RESULTS

Participants completed the 12-week exercise training

program, without any adverse events or exercise-induced

injury. The average adherence rate was 85%, with

adherence being defined as the percentage of scheduled

sessions attended and completed.

3.1. Exercise Performance

Following the 12-week exercise program, there were

no significant changes in exercise performance, however,

there were trends towards improvement in both time to

fatigue (804.6 ± 359.4 to 1483.8 ± 1110.2 sec; p = 0.08;

ES = 1.14) and distance to fatigue (3508.4 ± 3524.5 to

7412.6 ± 7773.1 m, p = 0.08; ES = 1.24) during the ex-

ercise performance test (Table 2).

3.2. Functional Outcomes

Following the 12-week exercise program, there was no

significant change in the composite score for the CUE

(Table 3). Likewise, when considering the subscales of

the CUE, there was no significant change in shoulder,

biceps, wrist extensor, triceps, or trunk function (Table

3). However, there was a trend towards an increase in the

CUE subscale pertaining to hand function following the

12-week exercise program (Table 3). There was no sig-

nificant change in upper limb function as determined by

the sf-QIF, or the SCI-SET, following the training pro-

gram (Table 3).

Table 2. Measures of exercise performance before and after 12

weeks of FES-arm ergometry.

Pre Post p-value ES

Time to

fatigue (sec)804.6 ± 359.4 1483.8 ± 1110.2 0.08 1.14

Distance to

fatigue (m)3508.4 ± 3524.57412.6 ± 7773.1 0.08 1.24

ES: Effect Size.

Ta bl e 3 . Measures of upper limb function before and after 12

weeks of FES-arm ergometry.

Scale Pre Post p-value ES

CUE (Composite )119.6 ± 49.4 127.6 ± 54.2 0.58 0.31

CUE (Subsets)

Shoulders 20.4 ± 11.122.2 ± 9.6 0.67 0.25

Biceps 21.0 ± 8.218.8 ± 8.1 0.35 0.48

Wrist Extensors19.2 ± 9.718.4 ± 9.5 0.78 0.21

Triceps 23.8 ± 10.123.0 ± 9.9 0.58 0.26

Hands 31.6 ± 12.838.0 ± 17.7 0.07 1.16

Trunk 5.2 ± 3.6 6.4 ± 5.0 0.18 1.01

sf-QIF 7.8 ± 9.8 9.2 ± 11.0 0.2 0.72

SCI-SET 122.6 ± 14.9 129.8 ± 9.2 0.23 0.72

CUE: Capabilities of Upper Extremity Questionnaire; sf-QIF: short form-

Quadriplegia Index of Function Questionnaire; SCI-SET: Spinal Cord Injury

Spasticity Evaluation Tool; ES: Effect Size.

J. Ptasinski et al. / Open Journal of Therapy and Rehabilitation 1 (2013) 17-21

3.3. Cardiovascular Outcomes

There was a statistically significant decrease in resting

MAP following the 12-week FES-arm ergometry pro-

gram (91.1 ± 14.0 to 87.7 ± 14.7 mmHg; p = 0.04; ES =

1.63), but there was no change in resting HR (66.8 ± 7.9

to 70.0 ± 10.1 beats/min; p = 0.14; ES = 1.06) (Table 4).

4. DISCUSSION

The current pilot study was preliminary in nature, and

thus the results should be interpreted with caution. Still,

the main finding of the current study was that individuals

with incomplete tetraplegia may experience decreases in

resting MAP following 12 weeks of FES-arm ergometry,

and although only trends were detected, this form of the-

rapy may also show promise for improving exercise per-

formance and self-reported hand function. Improvements

in exercise performance and hand function would have

obvious practical benefit. However, whether or not the

observed cardiovascular effects are clinically significant

is questionable. Individuals with SCI do experience

higher rates of cardiovascular disease, however, our par-

ticipants were normotensive both before and after the

training program and the magnitude of the reduction in

MAP was not profound. Still, this finding does hold pro-

mise for cardiovascular improvement following FES-arm

exercise and research in hypertensive participants with

SCI is warranted.

4.1. Exercise Performance

As mentioned, there were no significant changes in

exercise performance in the present study, although there

were trends for an increased time and distance to fatigue.

In related work, Coupaud and colleagues conducted a

pilot study investigating the effects of FES-arm ergome-

try on two individuals with tetraplegia [3]. In that pilot

work, the authors found variable results on exercise per-

formance that seemed to depend on functional ability.

Specifically, their more able participant (C6, AIS B, 18

years post-injury) showed increases in peak oxygen

uptake (0.7 to 1.1 L/min) and peak power output (7 to 38

Watts) following 12 weeks of progressive FES-arm ergo-

metry, while their less able participant (C6, AIS A, 8

months post-injury) made no improvement in peak oxy-

gen uptake and a smaller increase in peak power output

Table 4. Cardiovascular outcomes before and after 12 weeks of

FES-arm ergometry.

Pre Post p-value ES

MAP (mmHg) 91.1 ± 14.0 87.7 ± 14.7 0.04 1.63

HR (beats/min) 66.8 ± 7.9 70.0 ± 10.1 0.14 1.06

ES: Effect Size; HR: Heart Rate; MAP: Mean Arterial Pressure.

(3 to 8 Watts). The present study lacked the statistical

power to formally assess correlations between baseline

function and exercise-induced improvement. However,

anecdotally, our two most able participants did experi-

ence large improvements in exercise performance (289%

and 87% in time to fatigue; 336% and 78% in distance to

fatigue), while the others made little to no change. Fur-

ther research with larger samples is required to determine

the relationship between baseline function and the poten-

tial for benefit following FES-arm ergometry.

4.2. Upper Limb Function

There were no significant changes in the CUE when

considering the composite score for the group as a whole,

however, analyzing the separate subscales yielded more

encouraging results. Most notably, there was a trend for

an increase in hand function following the 12-week FES-

arm ergometry program, and these improvements were

observed in 4 of the 5 participants, while one participant

showed no change. This was an interesting finding, es-

pecially given that the biceps, triceps and shoulders were

electrically stimulated and not the hands or forearms.

Anecdotally, spinal cord injured individuals in our reha-

bilitation center, who did not participate in this study,

also reported improved hand function after using FES-

arm ergometry for their weekly therapy. It is not clear

why hand function improves despite no stimulation of

the hands or forearms. However, stimulating and strength-

ening the shoulders, biceps and triceps, may increase

upper limb stability while performing tasks that involve

the hands. Regarding the range of perceived benefits for

hand function, they seemed to encompass a fairly wide

array of gross and fine motor abilities, as the questions

pertained to a wide array of tasks. Further research is

certainly warranted to determine who may yield clini-

cally important benefits in hand function following FES-

arm ergometry, and what the optimal training stimuli are

to realize these results. Unfortunately, however, there

were no significant changes in biceps, triceps or shoulder

function, and this finding was surprising since those are

the muscles stimulated during the FES-arm ergometry.

Still, the lack of significant results for these data may be

due, in part, to the ceiling effect inherent in the CUE

questionnaire, as three of our participants had relatively

high baseline scores for the biceps and triceps. Nonethe-

less, there were participants with room to improve who

still showed no benefit in biceps or triceps function, and

further research is required to determine who may yield

upper limb benefit from FES-arm ergometry and to what

degree. There were also no significant changes on the sf-

QIF following the 12-week training program. This lack

of improvement may be due in small part to the ceiling

effect inherent in the questionnaire, as one participant

J. Ptasinski et al. / Open Journal of Therapy and Rehabilitation 1 (2013) 17-21

5. CONCLUSION

was either independent, or independent with devices, in

all 6 items at baseline. Still, consistent with the results of

the CUE, there were participants with room to improve

on the sf-QIF who showed no benefit following the trai-

ning. Furthermore, the lack of functional improvements

could be due to the nature of the exercise program, as it

was not intense enough to elicit functional improvements.

Training with FES at a continuous moderate intensity in-

creases cardiovascular function, as shown previously by

improvements in total aerobic capacity [3] and MAP in

the present study, but clearly, not functional tasks. Ac-

cordingly, our lab is currently experimenting with high

intensity FES training modes as a means for potentially

improving functional outcomes. Regarding the SCI-SET

scores, there were no significant changes for the group as

a whole, however, three of our five participants did ex-

perience moderate increases. This finding is interesting

as it illustrates that any functional improvements that

may ultimately be demonstrated with larger trials may be

due to increases in strength and muscular endurance, or

alternatively, decreases in muscle spasticity; or possibly

a combination of all three factors. Other studies with

larger sample sizes and a focus on strength, spasticity

and function will be required to answer these questions.

The current study demonstrated that individuals with

incomplete tetraplegia may experience positive changes

in resting blood pressure following 12 weeks of FES-arm

ergometry. In addition, although only trends were found,

our data justify further studies examining the potential

benefits of FES-arm ergometry on exercise performance

and upper limb function, and which individuals are most

likely to realize such benefits.

6. ACKNOWLEDGEMENTS

The authors would like to acknowledge the participants of this study

for their efforts and dedication. H. Sharif was supported by the Ontario

Neurotrauma Foundation.

REFERENCES

[1] Anderson, K.D. (2004) Targeting recovery: Priorities of

the spinal cord-injured population. Journal of Neuro-

trauma, 21, 1371-1383.

http://dx.doi.org/10.1089/neu.2004.21.1371

[2] Hicks, A.L., Martin Ginis, K.A., Pelletier, C.A., Ditor,

D.S., Foulon, B. and Wolfe, D.L. (2011) The effects of

exercise training on physical capacity, strength, body

composition and functional performance among adults

with spinal cord injury: A systematic review. Spinal Cord,

49, 1103-1127. http://dx.doi.org/10.1038/sc.2011.62

4.3. Study Limitations

The main limitation of the current study was the small

sample size. However, significant findings and some

very large effect sizes were still obtained. The other no-

table limitation was that function was only determined

by self-reported questionnaire. This type of data collec-

tion is advantageous as it represents real world function.

However, the particular questionnaires that were used in

the current study were susceptible to ceiling effects. As

such, it is possible that our more physically capable par-

ticipants, made functional gains that were not captured

by the testing methods employed. Further, as question-

naires were used as a measure of upper limb function, it

was perceived function that was specifically evaluated,

rather than actual function demonstrated in the lab.

Therefore, future studies with larger sample sizes, more

invasive measures of strength or muscle morphology,

and possibly a qualitative measure of function are war-

ranted to fully understand the potential benefits of FES-

arm ergometry.

[3] Coupaud, S., Gollee, H., Hunt, K.J., Fraser, M.H., Allan,

D.B. and McLean, A.N. (2008) Arm-cranking exercise

assisted by functional electrical stimulation in C6 tetra-

plegia: A pilot study. Technology and Health Care, 16,

415-427.

[4] Marino, R.J., Shea, J.A. and Stineman, M.G. (1998) The

capabilities of upper extremity instrument: Reliability and

validity of a measure of functional limitation in tetraple-

gia. Archives of Physical Medicine and Rehabilitation, 79,

1512-1521.

http://dx.doi.org/10.1016/S0003-9993(98)90412-9

[5] Marino, R.J. and Goin, J.E. (1999) Development of a

short-form quadriplegia index of function scale. Spinal

Cord, 37, 289-296.

http://dx.doi.org/10.1038/sj.sc.3100772

[6] Adams, M.M., Martin Ginis, K.A. and Hicks, A.L. (2007)

The spinal cord injury spasticity evaluation tool: Devel-

opment and evaluation. Archives of Physical Medicine

and Rehabilitation, 88, 1185-1192.

http://dx.doi.org/10.1016/j.apmr.2007.06.012

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