12th Annual Conference of the International FES Society
International FES Society
Voluntary breathing can influence motor functions of non-respiratory skeletal muscles, e.g., finger muscles. The influence was proposed to be mediated by the ventilation-associated enhancement on corticospinal excitability of the finger muscles, possibly including spinal mechanisms. Force responses to electrical stimulation include spinal mechanisms. The purpose was to investigate the potential spinal mechanism mediating the voluntary breathing effects on responses of finger extension forces to electrical stimulation. A single-pulse electrical stimulation of the same intensity was delivered to the extensor digitorum communis (EDC) during voluntary breathing (forced inspiration, IN and force expiration, OUT) and normal breathing (Norm) across various submaximal levels (10 ~30%) of isometric finger extension. Among the tested 3 subjects, differences of background finger extension forces were 2~3% at each force level. The evoked force increment was greater during IN and OUT than during Norm consistently at all tested force levels. However, the increment seemed not to be different between IN and OUT. Latency of the ES-evoked response was in the range from 52ms to 68ms. These pilot results demonstrated that voluntary breathing modulated finger extension force responses to electrical stimulation, most likely mediated by spinal mechanisms.