Effects of grip force on median nerve deformation at different wrist angles

Ping Yeap Loh; Hiroki Nakashima; Satoshi Muraki

doi:10.7717/peerj.2510

Effects of grip force on median nerve deformation at different wrist angles

PeerJ. 2016 Sep 22:4:e2510. doi: 10.7717/peerj.2510. eCollection 2016.

Authors

Ping Yeap Loh¹, Hiroki Nakashima², Satoshi Muraki³

Affiliations

¹ Department of Human Science, Graduate School of Design, Kyushu University, Fukuoka, Japan; Research Fellow of Japan Society for the Promotion of Science, Japan.
² Department of Human Science, Graduate School of Design, Kyushu University , Fukuoka , Japan.
³ Department of Human Science, Faculty of Design, Kyushu University , Fukuoka , Japan.

Abstract

The present study investigated the effects of grip on changes in the median nerve cross-sectional area (MNCSA) and median nerve diameter in the radial-ulnar direction (D1) and dorsal-palmar direction (D2) at three wrist angles. Twenty-nine healthy participants (19 men [mean age, 24.2 ± 1.6 years]; 10 women [mean age, 24.0 ± 1.6 years]) were recruited. The median nerve was examined at the proximal carpal tunnel region in three grip conditions, namely finger relaxation, unclenched fist, and clenched fist. Ultrasound examinations were performed in the neutral wrist position (0°), at 30°wrist flexion, and at 30°wrist extension for both wrists. The grip condition and wrist angle showed significant main effects (p < 0.01) on the changes in the MNCSA, D1, and D2. Furthermore, significant interactions (p < 0.01) were found between the grip condition and wrist angle for the MNCSA, D1, and D2. In the neutral wrist position (0°), significant reductions in the MNCSA, D1, and D2 were observed when finger relaxation changed to unclenched fist and clenched fist conditions. Clenched fist condition caused the highest deformations in the median nerve measurements (MNCSA, approximately -25%; D1, -13%; D2, -12%). The MNCSA was significantly lower at 30°wrist flexion and 30°wrist extension than in the neutral wrist position (0°) at unclenched fist and clenched fist conditions. Notably, clenched fist condition at 30°wrist flexion showed the highest reduction of the MNCSA (-29%). In addition, 30°wrist flexion resulted in a lower D1 at clenched fist condition. In contrast, 30°wrist extension resulted in a lower D2 at both unclenched fist and clenched fist conditions. Our results suggest that unclenched fist and clenched fist conditions cause reductions in the MNCSA, D1, and D2. More importantly, unclenched fist and clenched fist conditions at 30°wrist flexion and 30°wrist extension can lead to further deformation of the median nerve.

Keywords: Clenched fist; Grip strength; Median nerve cross-sectional area; Median nerve diameter; Unclenched fist.

Grants and funding

This work is partially supported by JSPS KAKENHI Grant Number JP16J01964. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.