The effects of hybrid functional electrical stimulation interval training on aerobic fitness and fatigue in people with advanced multiple sclerosis: An exploratory pilot training study

Background: Improving aerobic fitness in people with advanced multiple sclerosis (MS) may reduce fatigue, and lower the risk of cardiovascular disease, as has been found for people with mild to moderate MS. Training targeting aerobic fitness can be challenging due to paresis, access to suitable equipment and fatigue. The aim of this study was to investigate whether people with advanced multiple sclerosis could perform functional electrical stimulation (FES) cycling combined with arm crank interval exercise (hybrid FES interval training) training, and its effects on aerobic fitness and fatigue. Methods: Hybrid FES interval training was performed 2 d/wk for 12 weeks. Each session consisted of 40 min of continuous FES cycling with arm crank intervals of 30 s work/30 s rest added concurrently for 20 min. The intensity target was a minimum of 60 % of arm crank power and 'hard' measured by rate of perceived exertion (RPE). Attendance, compliance to intensity and time targets, adverse events, and drop outs were measured. Aerobic fitness was assessed by an arm crank maximal test. Fatigue was measured via the Modified Fatigue Impact Scale (MFIS). Results: Seven participants (6 female; age 57.1 +/- 7.8y; Expanded Disability Status Scale 7.1 +/- 0.8) with advanced MS attended 80 +/- 10.4 % of the scheduled exercise sessions and there were no adverse events or drop outs. Average RPE at the end of each training session was 15.1 +/- 2.1, representing vigorous intensity exercise. Aerobic fitness did not change pre- to post-intervention (14.2 +/- 5.7 to 14.8 +/- 6.0 mL/kg/min [p = 0.43]), and resulted in a small effect size (ES) (0.30). The reduction in fatigue during the intervention (31.0 +/- 10.4 to 21.7 +/- 11.4 [p = 0.10]), resulted in a moderate to large ES (-0.77). Conclusion: Hybrid FES interval training could be performed 2 days per week for 12 weeks and represented vigorous intensity exercise, but there was no change in aerobic fitness. The reduction in participants' perceptions of fatigue represented a moderate to large ES, indicating hybrid FES interval training might be suitable for people with advanced MS who need exercise equipment appropriate for their condition. Clinical Trial Registration: This study was registered with Australian and New Zealand Clinical Trials Register (U1111-1194-2040).