Effects of sex and joint action on voluntary activation

Ryoichi Ema; Momoka Suzuki; Emi Kawaguchi; Itaru Saito; Ryota Akagi

doi:10.7717/peerj.5968

Effects of sex and joint action on voluntary activation

PeerJ. 2018 Nov 15:6:e5968. doi: 10.7717/peerj.5968. eCollection 2018.

Authors

Ryoichi Ema¹, Momoka Suzuki², Emi Kawaguchi³, Itaru Saito², Ryota Akagi^{2

4}

Affiliations

¹ School of Management, Shizuoka Sangyo University, Iwata, Japan.
² College of Systems Engineering and Science, Shibaura Institute of Technology, Saitama, Japan.
³ Graduate School of Human Sciences, Waseda University, Tokorozawa, Japan.
⁴ Graduate School of Engineering and Science, Shibaura Institute of Technology, Saitama, Japan.

Abstract

The current study tested the hypothesis that voluntary activation during maximal voluntary contraction (MVC) conditionally depends on sex and joint action. Twenty-eight healthy adults (14 of each sex) performed knee extensor MVC and plantar flexor MVC at extended and flexed knee positions. Voluntary activation during MVC was assessed using a twitch interpolation technique. The voluntary activation during plantar flexor MVC at the extended knee position was significantly lower (P = 0.020, 95% confidence interval 1.4 to 14.6, Cohen's d for between-subject design = 0.94) in women (88.3% ± 10.0%) than in men (96.2% ± 6.6%). In contrast, no significant sex differences were shown in the voluntary activation during knee extensor MVC (93.7% ± 5.9% (women) vs. 95.0% ± 3.9% (men)) and during plantar flexor MVC at the flexed knee position (90.4% ± 12.2% (women) vs. 96.8% ± 5.6% (men)). The voluntary activation during knee extensor MVC was significantly higher (P = 0.001, 95% confidence interval 2.1 to 8.8, Cohen's d for within-subject design = 0.69) than that during plantar flexor MVC at the extended knee position in women, whereas the corresponding difference was not observed in men. The results revealed that the existence of sex difference in the voluntary activation during MVC depends on joint action and joint angle.

Keywords: Knee extension; Plantar flexion; Sex difference; Twitch interpolation technique.

Grants and funding

This work was supported in part by the grant from the Nakatomi Foundation and JSPS KAKENHI Grant Numbers JP16K01671/JP16H05918. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.