Fatigue and Discomfort During Spatially Distributed Sequential Stimulation of Tibialis Anterior.

Neuromuscular electrical stimulation is conventionally applied through a single pair of electrodes over the muscle belly (Single Electrode Stimulation, SES). SES is limited by discomfort and incomplete motor-unit recruitment, restricting electrically-evoked torque and promoting premature fatigue-induced torque-decline. Sequential stimulation, involving rotation of pulses between multiple pairs of electrodes, has been proposed as an alternative (Spatially Distributed Sequential Stimulation, SDSS). The present aim was to compare discomfort, maximal-tolerated torque and fatigue-related outcomes between SES and SDSS of tibialis anterior. Ten healthy participants completed two experimental sessions. The self-reported discomfort at sub-maximal torque, the maximal-tolerated torque, fatigue-induced torque-decline during, and doublet-twitch torque at 10-and 100-Hz before and after, 300 intermittent (0.6-s-ON-0.6-s-OFF) isokinetic contractions were compared between SES and SDSS. SDSS stimulation improved fatigue-related outcomes, whereas increased discomfort and reduced maximal-tolerated torque. SDSS holds promise for reducing fatigue. However, limited torque production and associated discomfort may limit its utility for rehabilitation/training.