Twitch potentiation induced by two different modalities of neuromuscular electrical stimulation: Implications for motor unit recruitment

Abstract

ABSTRACTIntroduction: We tested the hypothesis that twitch potentiation would be greater following conventional (CONV) neuromuscular electrical stimulation (50‐µs pulse width and 25‐Hz frequency) compared with wide‐pulse high‐frequency (WPHF) neuromuscular electrical stimulation (1‐ms, 100‐Hz) and voluntary (VOL) contractions, because of specificities in motor unit recruitment (random in CONV vs. random and orderly in WPHF vs. orderly in VOL). Methods: A single twitch was evoked by means of tibial nerve stimulation before and 2 s after CONV, WPHF, and VOL conditioning contractions of the plantar flexors (intensity: 10% maximal voluntary contraction; duration: 10 s) in 13 young healthy subjects. Results: Peak twitch increased (P < 0.05) after CONV (+4.5 ± 4.0%) and WPHF (+3.3 ± 5.9%), with no difference between the 2 modalities, whereas no changes were observed after VOL (+0.8 ± 2.6%). Conclusions: Our results demonstrate that presumed differences in motor unit recruitment between WPHF and CONV do not seem to influence twitch potentiation results. Muscle Nerve 51: 412–418, 2015