Elbow Joint Angles in Elbow Flexor Unilateral Resistance Exercise Training Determine Its Effects on Muscle Strength and Thickness of Trained and Non-trained Arms

Shigeru Sato; Riku Yoshida; Ryosuke Kiyono; Kaoru Yahata; Koki Yasaka; João Pedro Nunes; Kazunori Nosaka; Masatoshi Nakamura

doi:10.3389/fphys.2021.734509

Elbow Joint Angles in Elbow Flexor Unilateral Resistance Exercise Training Determine Its Effects on Muscle Strength and Thickness of Trained and Non-trained Arms

Front Physiol. 2021 Sep 16:12:734509. doi: 10.3389/fphys.2021.734509. eCollection 2021.

Authors

Shigeru Sato¹, Riku Yoshida¹, Ryosuke Kiyono¹, Kaoru Yahata¹, Koki Yasaka², João Pedro Nunes³, Kazunori Nosaka⁴, Masatoshi Nakamura^{1

2}

Affiliations

¹ Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan.
² Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan.
³ Metabolism, Nutrition, and Exercise Laboratory, Physical Education and Sport Center, Londrina State University, Londrina, Brazil.
⁴ Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia.

Abstract

The present study compared two unilateral arm curl resistance exercise protocols with a different starting and finishing elbow joint angle in the same ROM for changes in elbow flexors strength and muscle thickness of the trained and non-trained arms. Thirty-two non-resistance trained young adults were randomly assigned to one of the three groups: extended joint training (0°-50°; EXT, n = 12); flexed joint training (80°-130°; FLE, n = 12); and non-training control (n = 8). The exercise training was performed by the dominant arms twice a week for 5 weeks with gradual increases in the training volume over 10 training sessions, and the non-dominant (non-trained) arms were investigated for the cross-education effect. Maximal voluntary contraction torque of isometric (MVC-ISO), concentric (MVC-CON), and eccentric contractions (MVC-ECC), and thickness (MT) of biceps brachii and brachialis of the trained and non-trained arms were assessed at baseline and 4-8 days after the last training session. The control group did not show significant changes in any variables. Significant (P < 0.05) increases in MVC-ISO torque (16.2 ± 12.6%), MVC-CON torque (21.1 ± 24.4%), and MVC-ECC torque (19.6 ± 17.5%) of the trained arm were observed for the EXT group only. The magnitude of the increase in MT of the trained arm was greater (P < 0.05) for EXT (8.9 ± 3.9%) than FLE (3.4 ± 2.7%). The cross-education effect was evident for MVC-ISO (15.9 ± 14.8%) and MVC-CON (16.7 ± 20.0%) torque of the EXT group only. These results suggest that resistance training at the extended elbow joint induces greater muscle adaptations and cross-education effects than that at flexed elbow joint.

Keywords: concentric; cross-education effect; eccentric; isometric; maximal voluntary contraction torque; range of motion.