The effects of releasing ankle joint on pedal force and power production during electrically stimulated cycling in paraplegic individuals: A pilot study

Abstract

Previous research has investigated functional electrical stimulation (FES) cycle force and power output (PO) from the perspective of knee and hip joint biomechanics. However, ankle-foot biomechanics and, in particular, the effect of releasing the ankle joint on cycle pedal force and PO during FES cycling in paraplegics has not been widely explored. Therefore, the purpose of this study is to determine whether releasing the ankle joint might influence the peak pedal force and PO during FES cycling in paraplegics. Three complete paraplegics (C7 – T4) participated in this study. All participants performed two sessions of cycling in randomized order. Session 1 and 2 required the participants to cycle in fixed and free-ankle setup, respectively. For each session, the participants performed two sub-sessions of FES cycling. During sub-session 1, the muscles stimulated were upper leg muscles [quadriceps (QUAD) and hamstrings (HAM)]. In sub-session 2, both upper and lower leg muscles [QUAD, HAM, tibialis anterior (TA) and triceps surae (TS)] were stimulated. The normalized peak pedal force and PO of each condition were analyzed. Overall, the normalized peak pedal force and PO during fixed-ankle FES cycling is higher than free-ankle FES cycling. Stimulation of both upper and lower leg muscles during FES cycling provided higher normalized peak pedal force and PO compared to the upper leg muscles stimulated alone. The present pilot study revealed that fixed-ankle FES cycling produced higher normalized peak pedal force and PO than free-ankle FES cycling. Future work involving more paraplegics will be investigated. This finding might serve as a reference for future rehabilitative cycling protocols.