Conduction Velocity of Muscle Action Potential of Knee Extensor Muscle During Evoked and Voluntary Contractions After Exhaustive Leg Pedaling Exercise

Kohei Watanabe; Taiki Sakai; Shosaku Kato; Natsuka Hashizume; Naoki Horii; Maki Yoshikawa; Natsuki Hasegawa; Keiko Iemitsu; Katsunori Tsuji; Masakata Uchida; Masao Kanamori; Motoyuki Iemitsu

doi:10.3389/fphys.2020.00546

Conduction Velocity of Muscle Action Potential of Knee Extensor Muscle During Evoked and Voluntary Contractions After Exhaustive Leg Pedaling Exercise

Front Physiol. 2020 May 27:11:546. doi: 10.3389/fphys.2020.00546. eCollection 2020.

Authors

Affiliations

¹ Laboratory of Neuromuscular Biomechanics, School of International Liberal Studies, Chukyo University, Nagoya, Japan.
² Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan.
³ Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan.
⁴ Research Organization of Science and Technology, Ritsumeikan University, Kusatsu, Japan.

Abstract

Purpose: Muscle fiber conduction velocity (CV) has been developed to estimate neuromuscular fatigue and measured during voluntary (VC) and electrically evoked (EC) contractions. Since CV during VC and EC reflect different physiological phenomena, the two parameters would show inconsistent changes under the conditions of neuromuscular fatigue. We investigated the time-course changes of CV during EC and VC after fatiguing exercise.

Methods: In 14 young males, maximal voluntary contraction (MVC) of knee extensor muscles, CV during electrical stimulation (CV-EC) and MVC (CV-VC) were measured before and immediately, 30 min, 60 min, 120 min, and 24 h after exhaustive leg pedaling exercise.

Results: CV-EC significantly increased immediately after the fatiguing exercise (p < 0.05) and had a significant negative correlation with MVC in merged data from all time-periods (r = -0.511, p < 0.001). CV-VC significantly decreased 30, 60, and 120 min after the fatiguing exercise (p < 0.05) and did not show any correlations with MVC (p > 0.05).

Conclusion: These results suggest that CV during EC and VC exhibits different time-course changes, and that CV during EC may be appropriate to estimate the degree of neuromuscular fatigue after fatiguing pedaling exercise.

Keywords: cycling; multi-channel surface electromyography; neuromuscular fatigue; quadriceps; vastus lateralis.