Skeletal muscle conditioning may be an effective rehabilitation intervention preceding functional electrical stimulation cycling.

Abstract

In our recent effort, we introduced a submaximal index that utilized ventilatory efficiency relative to CO2 production (VE/CO2) to evaluate the cardiovascular effectiveness to functional electrical stimulation lower-extremity cycling (FES-LEC) in persons with spinal cord injury (SCI) (Gorgey and Lawrence, 2016). When compared to the resting state, we found that an acute bout of FES-LEC resulted in increased ventilation during exercise and a significant decrease of approximately 22% in the VE/CO2 ratio, suggesting that this ratio could be utilized to monitor the cardiovascular response during submaximal FES-LEC in the SCI population. The study demonstrated that a potential limitation to the FES-LEC application is a heavy reliance on carbohydrate storage as a main source of substrate utilization. Reliance on carbohydrate utilization, transformation to fast-twitch fibers following SCI and random muscle recruitment are likely to introduce rapid muscle fatigue during FES-LEC applications. This may limit oxygen uptake and outcomes regarding cardiovascular profile. In this perspective, we propose that skeletal muscle conditioning via surface neuromuscular electrical stimulation (NMES) may be an essential rehabilitation intervention to improve the outcomes of FES-LEC applications.