Low-level voluntary input enhances corticospinal excitability during ankle dorsiflexion neuromuscular electrical stimulation in healthy young adults

PLoS One. 2023 Mar 8;18(3):e0282671. doi: 10.1371/journal.pone.0282671. eCollection 2023.

Abstract

Previous evidence indicated that interventions with combined neuromuscular electrical stimulation (NMES) and voluntary muscle contractions could have superior effects on corticospinal excitability when the produced total force is larger than each single intervention. However, it is unclear whether the superior effects exist when the produced force is matched between the interventions. Ten able-bodied individuals performed three intervention sessions on separate days: (i) NMES-tibialis anterior (TA) stimulation; (ii) NMES+VOL-TA stimulation combined with voluntary ankle dorsiflexion; (iii) VOL-voluntary ankle dorsiflexion. Each intervention was exerted at the same total output of 20% of maximal force and applied intermittently (5 s ON / 19 s OFF) for 16 min. Motor evoked potentials (MEP) of the right TA and soleus muscles and maximum motor response (Mmax) of the common peroneal nerve were assessed: before, during, and for 30 min after each intervention. Additionally, the ankle dorsiflexion force-matching task was evaluated before and after each intervention. Consequently, the TA MEP/Mmax during NMES+VOL and VOL sessions were significantly facilitated immediately after the interventions started until the interventions were over. Compared to NMES, larger facilitation was observed during NMES+VOL and VOL sessions, but no difference was found between them. Motor control was not affected by any interventions. Although superior combined effects were not shown compared to voluntary contractions alone, low-level voluntary contractions combined with NMES resulted in facilitated corticospinal excitability compared to NMES alone. This suggests that the voluntary drive could improve the effects of NMES even during low-level contractions, even if motor control is not affected.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ankle* / physiology
  • Electric Stimulation / methods
  • Electromyography
  • Evoked Potentials, Motor / physiology
  • Humans
  • Muscle Contraction / physiology
  • Muscle, Skeletal* / physiology
  • Transcranial Magnetic Stimulation / methods
  • Young Adult

Grants and funding

This study was supported by the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI https://www.jsps.go.jp/english/) [awarded to KN (#18H04082, #18KK0272) and MM (#19K23606 and #20K19412)] and the CREST grant from the Japan Science and Technology Agency (https://www.jst.go.jp/kisoken/crest/en/index.html) awarded to KN.