Ché Fornusek

Cardiorespiratory, metabolic, and biomechanical responses during functional electrical stimulation leg exercise: health and fitness benefits.

Functional electrical stimulation (FES)-induced leg exercise offers the potential for individuals with lower-limb paralysis to otherwise gain some benefits conferred by leg exercise. Although its original intent is to reactivate the leg muscles to produce functional upright mobility, as a rehabilitation therapy, FES-evoked exercise increases the whole-body metabolism of individuals with spinal cord injury (SCI) so that they may gain general and localized health and fitness benefits. The physiological and psychosocial responses during FES-evoked cycling, standing, rowing, leg extension, or stepping have been extensively explored for over 20 years. Some of the advantages of such exercise include augmented cardiorespiratory fitness, promotion of leg blood circulation, increased activity of specific metabolic enzymes or hormones, greater muscle volume and fiber size, enhanced functional exercise capacity such as strength and endurance, and altered bone mineral density. Positive psychosocial adaptations have also been reported among SCI individuals who undergo FES exercise. This article presents a position review of the available literature on the effects of FES-evoked exercise since the earliest date until 2007, to warrant a conclusion about the current status and potential of FES-evoked exercise for paralyzed people.

Development of an Isokinetic Functional Electrical Stimulation Cycle Ergometer

An isokinetic functional electrical stimulation leg cycle ergometer (iFES‐LCE) was developed for individuals with spinal cord injury (SCI). The iFES‐LCE was designed to allow cycle training over a broad range of pedalling cadences (5–60 rev/min) to promote both muscular strength and cardiorespiratory fitness. A commercially available motorized cycle ergometer was integrated with a custom built FES system, a laptop computer, and a specialized chair that restricted lateral leg movements. Sample biomechanical data were collected from an SCI subject performing FES cycling to demonstrate the iFES‐LCEs performance characteristics. Calibration of the iFES‐LCE system revealed a linear relationship between torque applied to the axle of the motorized ergometer and the braking motor current generated to maintain velocity. Performance data derived from iFES‐LCE motor torque agreed closely with similar data collected using strain‐gauge instrumented pedals (cross‐correlations = 0.93–0.98). The iFES‐LCE was shown to work well across a range of pedaling cadences. We conclude that the new iFES‐LCE system may offer improved training potential by allowing cycling over a broad range of pedaling cadences, especially low cadence. This device also improves upon the accuracy of other ergometers by adjusting for the passive load of the legs.

Maximizing muscle force via low-cadence functional electrical stimulation cycling.

OBJECTIVE This study investigated the effect of pedal cadence upon torque production, power output and muscle fatigue rates during functional electrical stimulation evoked cycling in spinal cord injured individuals. SUBJECTS All subjects had complete thoracic spinal cord injuries T4-T9 (ASIA A) and had been functional electrical stimulation training regularly for at least 6 months. METHODS One trial (n = 8) examined a low vs high pedal rate (20 and 50 rev x min(-1)) upon isolated muscle fatigue over 5 minutes. A second trial (n = 9) investigated the effect of cadence (15 vs 50 rev x min(-1)) upon performance during 35-minutes of functional electrical stimulation evoked cycling. RESULTS Peak torque produced by left quadriceps decayed significantly faster at the higher pedal cadence, indicating a higher rate of muscle fatigue. Functional electrical stimulation cycling over 35 minutes also revealed that peak and average torques were significantly greater at the lower cadence. From 15 minutes onwards, power output was significantly higher at 50 rev x min(-1) FES-cycling, compared with 15 rev x min(-1). CONCLUSION The higher muscle forces observed during low cadence functional electrical stimulation cycling should offer improvements over traditional pedalling velocities for training leg strength in individuals with spinal cord injury.

Cardiovascular and Metabolic Responses During Functional Electric Stimulation Cycling at Different Cadences

OBJECTIVE To determine the influence of pedaling cadence on cardiorespiratory responses and muscle oxygenation during functional electric stimulation (FES) leg cycling. DESIGN Repeated measures. SETTING Laboratory. PARTICIPANTS Nine subjects with T4 through T10 spinal cord injury (SCI) (American Spinal Injury Association grade A). INTERVENTIONS FES cycling was performed at pedaling cadences of 15, 30, and 50 revolutions per minute (rpm). MAIN OUTCOME MEASURES At each cadence, heart rate, oxygen uptake, and cardiac output were recorded during 35 minutes of cycling. Near infrared spectroscopy was used to quantify quadriceps muscle oxygenation. RESULTS All pedaling cadences induced similar elevations in cardiorespiratory metabolism, compared with resting values. Higher average power output was produced at 30rpm (8.2+/-0.7W, P<.05) and 50rpm (7.9+/-0.5W, P<.05) compared with 15rpm (6.3+/-0.6W). Gross mechanical efficiency was significantly higher (P<.05) at 30 and 50rpm than at 15rpm. Quadriceps muscle oxygenation did not differ with pedaling cadences. CONCLUSIONS Cardiorespiratory responses and muscle metabolism adjustments during FES leg cycling were independent of pedal cadence. FES cycling at a cadence of 50rpm may not confer any advantages over 30 or 15rpm for cardiovascular fitness promotion in persons with SCI.

EXTERNAL POWER OUTPUT CHANGES DURING PROLONGED CYCLING WITH ELECTRICAL STIMULATION

This study analysed external power output and physiologic responses in 5 individuals with paraplegia during 40 minutes of electrical stimulation leg cycle exercise. Cycling was performed on a motor-driven isokinetic ergometer that enabled precise determinations of power output. Electrical stimulation was increased to 120-140 mA within the first 5 minutes and remained constant thereafter. Power output increased to 10.7 +/- 3.0 W after 2 minutes, dropped to 5.3 +/- 1.8 W after 6 minutes and subsequently recovered to 8.2 +/- 2.2 and 6.1 +/- 2.3 W after 19.5 and 40 minutes, respectively. Oxygen consumption increased to 0.47 +/- 0.09 l/min after 6 minutes and declined during the second half of the exercise bout. Gross mechanical efficiency after 19.5 minutes was elevated compared with the value after 6 minutes. Heart rate was significantly increased at the end of the trial. The time-dependent variability of power output and physiological responses question the concept of steady state for this form of exercise.

Pilot Study of the Effect of Low-Cadence Functional Electrical Stimulation Cycling After Spinal Cord Injury on Thigh Girth and Strength

OBJECTIVE To investigate the long-term effects of functional electrical stimulation (FES)-evoked cycle training cadence on leg muscle hypertrophy and electrically evoked strength. DESIGN Open intervention study. SETTING Laboratory setting. PARTICIPANTS Untrained individuals with chronic spinal cord injury (N=8). INTERVENTIONS Six weeks (3d/wk) of training on an isokinetic FES cycle ergometer. For each subject, 1 leg was randomly allocated to cycling at 10 revolutions per minute (rpm) (LOW) for 30min/d, and the other cycling at 50rpm (HIGH) for 30min/d. MAIN OUTCOME MEASURES Pre- and posttraining measurements of lower limb circumference were performed at the distal and middle position of each thigh. Electrically evoked quadriceps muscle torque during an isometric contraction was also assessed. RESULTS Six weeks of FES cycle training significantly increased thigh girth in both LOW and HIGH groups. At midthigh, girth increases induced by LOW (6.6%±1.2%) were significantly greater than those by HIGH (3.6%±0.8%). LOW also produced greater gains in electrically evoked isometric torque than HIGH after training. CONCLUSIONS These results suggest that lower pedaling cadences evoke greater muscle hypertrophy and electrically stimulated muscle strength compared with higher cadences.

Electrical stimulation plus progressive resistance training for leg strength in spinal cord injury: A randomized controlled trial

Study design:A randomized controlled trial.Objectives:To determine the effectiveness of electrical stimulation (ES)-evoked muscle contractions superimposed on progressive resistance training (PRT) for increasing voluntary strength in the quadriceps muscles of people with spinal cord injuries (SCI).Setting:Sydney, Australia.Methods:A total of 20 people with established SCI and neurologically induced weakness of the quadriceps muscles participated in the trial. Participants were randomized between experimental and control groups. Volunteers in the experimental group received ES superimposed on PRT to the quadriceps muscles of one leg thrice weekly for 8 weeks. Participants in the control group received no intervention. Assessments occurred at the beginning and at the end of the 8-week period. The four primary outcomes were voluntary strength (Nm) and endurance (fatigue ratio) as well as the performance and satisfaction items of the Canadian Occupational Performance Measure (COPM; points).Results:The between-group mean differences (95% confidence interval (CI)) for voluntary strength and endurance were 14 Nm (1–27; P=0.034) and 0.1 (−0.1 to 0.3; P=0.221), respectively. The between-group median differences (95% CI) for the performance and satisfaction items of the COPM were 1.7 points (−0.2 to 3.2; P=0.103) and 1.4 points (−0.1 to 4.6; P=0.058), respectively.Conclusion:ES superimposed on PRT improves voluntary strength, although there is uncertainty about whether the size of the treatment effect is clinically important. The relative effectiveness of ES and PRT is yet to be determined.

Systematic review of exercise for Charcot-Marie-Tooth disease

Charcot‐Marie‐Tooth disease (CMT) is a slowly progressive hereditary degenerative disease and one of the most common neuromuscular disorders. Exercise may be beneficial to maintain strength and function for people with CMT, however, no comprehensive evaluation of the benefits and risks of exercise have been conducted. A systematic review was completed searching numerous electronic databases from earliest records to February 2015. Studies of any design including participants of any age with confirmed diagnosis of CMT that investigated the effects of exercise were eligible for inclusion. Of 13,301 articles identified following removal of duplicates, 11 articles including 9 unique studies met the criteria. Methodological quality of studies was moderate, sample sizes were small, and interventions and outcome measures used varied widely. Although the majority of the studies identified changes in one or more outcome measurements across exercise modalities, the majority were non‐significant, possibly due to Type II errors. Significant effects described included improvements in strength, functional activities, and physiological adaptations following exercise. Despite many studies showing changes in strength and function following exercise, findings of this review should be met with caution due to the few studies available and moderate quality of evidence. Well‐powered studies, harmonisation of outcome measures, and clearly described interventions across studies would improve the quality and comparability of the evidence base. The optimal exercise modality and intensity for people with CMT as well as the long‐term safety of exercise remain unclear.

nEuRoMuSculAR ElEctRIcAl StIMulA tIon cyclIng ExERcISE FoR PERSonS WIth ADv AncED MultIPlE SclERoSIS

OBJECTIVE To investigate the feasibility of neuromuscular electrical stimulation cycling modified to suit persons with advanced multiple sclerosis. SUBJECTS Eight women with secondary progressive multiple sclerosis. METHODS Subjects participated in an 18-session (40 min) neuromuscular electrical stimulation cycling program. A pedaling cadence of 10 rev•min-1 was employed and stimulation intensity was not modulated to control cadence, but increased gradually throughout each session. The outcomes included the stimulation intensity tolerated, thigh circumference changes, and power output and cardiorespiratory response during cycling. Participants were interviewed about perceived benefits of the treatment including changes in transfer ability. RESULTS Seven participants (Expanded Disability Status Scale 6.5-8.5) (mean 7.4 (standard deviation 0.7)) completed the training program over an average of 10 weeks. Greater stimulation intensities were tolerated than previously reported for persons with multiple sclerosis. Increases were found in thigh volume. Perceived benefits included improvements in transfer ability, leg circulation, spasticity and strength. CONCLUSION Modifying neuromuscular electrical stimulation cycling allowed persons with advanced multiple sclerosis to tolerate greater stimulation intensities and exercise their muscles more intensely than previous studies. The benefits reported, which were solely due to neuromuscular electrical stimulation cycling, demonstrate that persons with preserved sensation and muscle paralysis/paresis might benefit from neuromuscular electrical stimulation exercise when it is adjusted appropriately.

Evoked EMG and muscle fatigue during isokinetic FES-cycling in individuals with SCI.

Purpose:  This study investigated whether muscle fatigue during functional electrical stimulation (FES)‐induced cycling was associated with changes occurring in evoked electromyographic signals (eEMG, M‐waves) in individuals with spinal cord injury. We also explored the effects of recovery intervals between exercise sessions on the relationship between eEMG and muscle torque.