Hybrid high-intensity interval training using functional electrical stimulation leg cycling and arm ski ergometer for people with spinal cord injuries: a feasibility study

AIM: The aim was to assess safety and feasibility of Hybrid High-Intensity Interval Training (HIIT) using Functional Electrical Stimulation (FES) leg cycling and arm ski ergometer in people with Spinal Cord Injuries (SCI). METHOD: Eight outpatients (mean age 42.8 years; 7 men) with stable SCI paraplegia (mean 14.5 years since injury) participated in hybrid HIIT (90% peak watts; 4 × 4–min intervals), three times a week (over 8 weeks). Primary outcomes were Adverse Events (AE), participant acceptability, shoulder pain, training intensity (% peak watts), and attendance. Secondary outcomes were effect on peak oxygen uptake (VO(2)peak) during FES hybrid poling, mean watts, self-reported leisure time physical activity, quality of life, and fatigue. RESULTS: No serious AE occurred; acceptability with the training modality was high, while shoulder pain increased by 9% (SD 95.2). During training, 50% of the participants reached > 90% peak watts during the intervals, three with the legs (FES cycle) and one with the arms (Ski-Erg). Overall, mean training intensity (% peak watts) was 92% (SD 18.9) for legs and 82% (SD 10.3) for arms. Proportion of fulfilled training minutes was 82% (range 36–100%); one participant dropped out after 6 weeks due to back pain. Mean VO(2)peak increased by 17% (SD 17.5). Participants reported increased leisure time physical activity and health-related quality of life, besides reduced fatigue. CONCLUSION: Hybrid HIIT was safe for people with SCI paraplegia. The majority of the criteria for feasibility were met with acceptable attendance rate, limited drop out, participants enjoyed training, and increased VO(2)peak and mean watts. However, the intensity of 90% peak watts was reached by < 60% of the participants despite high RPE ratings during training. The method of measuring and calculating intensity needs to be studied further before a study using this HIIT protocol is undertaken. TRIAL REGISTRATION: Clinicaltrials.gov, NCT04211311, registered 12 December 2019 retrospectively registered SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40814-022-00997-2.