Functional Electrical Stimulation Cycling and Muscle Oxidative Capacity in Two Non-Ambulatory People with MS

Background: People with multiple sclerosis (MS) who are non-ambulatory are challenged by the negative impact of decreased mobility on their health and function. Decreased mobility leads to deconditioning that can cause secondary conditions and further functional decline. Exercise has been shown to have positive effects on health measures in people with MS; however, options for exercise are limited in those who use a wheelchair. Functional electrical stimulation (FES) cycling is one intervention accessible to people who use a wheelchair. The use of surface electrodes to stimulate the leg muscles during cycling may provide enough exercise to induce changes in health measures. FES cycling does not appear to cause an increase in symptoms in people with MS. However, little is known about the effect of FES cycling on muscle in people with MS, known to have impaired central nervous system input as well as impaired muscle metabolism. Muscle response to FES cycling may provide insights to assist with exercise prescription for people with MS who are non-ambulatory.

Objectives: To describe differences in FES cycling performance and muscle oxidative capacity in two non-ambulatory individuals with MS who participated in a 4-week FES cycling intervention.

Methods: Participants were part of a larger trial in which they trained on an FES cycle 30 mins/day, 2-3 days/week for 4 weeks. FES cycling performance was collected during each session. Muscle oxidative capacity (mVO₂) was measured in the right vastus lateralis muscle using near infrared spectroscopy before and after the FES cycling training program.

Results: Both individuals safely exercised on the FES cycle for 4 weeks, without adverse events. Both presented with mVO₂ lower than that in able-bodied individuals. One was able to increase time and resistance during cycling over the 4-week period. She also demonstrated greater mVO₂ than the participant who was unable to improve cycling performance; she also had an increase in mVO₂ after training, while the other participant showed a decrease.

Conclusions: Muscle oxidative capacity may influence muscle performance in people with MS who are non-ambulatory. Exercise may impact muscle oxidative capacity and function. This may be an important consideration when prescribing exercise and choosing interventions for people with MS who are non-ambulatory. The relationship between exercise and muscle oxidative capacity requires further investigation in people with MS.