Study on the FES effects of different sizes of stimulation electrodes and different numbers of stimulation channels

This study aims to investigate the functional electrical stimulation (FES) effects of different sizes of stimulation electrodes and different numbers of stimulation channels. Taking the biceps brachii as the target muscle, four FES electrode configurations were designed, varying in electrode size and stimulation channel number. This study recruited ten healthy subjects. Under each FES electrode configuration, a high (30 Hz)-frequency/low (1 Hz)-frequency alternating stimulation was conducted to collect effective muscle contraction strength data and surface electromyography (sEMG) signals. The effects of different FES electrode configurations on muscle contraction strength were analyzed using fatigue-related indicators, and those on myoelectric activity property involving motion unit (MU) recruitment and muscle fiber conduction velocity (MFCV) were explored by means of sEMG data analysis. Both enlarging stimulation electrode size and increasing the number of stimulation channels delayed muscle fatigue, enhanced motor unit recruitment, and generated stronger muscle contractions at the same current intensity. Enlarging the electrode size is more conducive to recruiting more MUs and enhancing muscle contraction output, while increasing the number of stimulation channels is more conducive to delaying muscle fatigue effects. The research results of this article can provide scientific guidance for clinical doctors to develop personalized FES plans, thereby improving treatment effect.