Although the moment arm of the triceps brachii muscle has been shown to be associated with the muscle’s anatomical crosssectional area, whether training-induced muscle hypertrophy alters the moment arm of the muscle remains unexplored. Therefore, the current study aimed to examine this. Eleven men underwent a 12-week resistance training program for the triceps brachii muscle. The maximum muscle anatomical cross-sectional area (ACSAmax), the moment arm of the triceps brachii muscle, and the anterior-posterior dimension of the olecranon were measured using a magnetic resonance imaging system before and after intervention. The ACSAmax (33.6 ± 11.9%, P < .001) and moment arm (5.5 ± 4.0%, P = .001) significantly increased after training, whereas the anterior-posterior dimension of the olecranon did not change (P > .05). The change in moment arm was smaller than that expected from the relationship between the ACSAmax and the moment arm before the intervention. The present results indicate that training-induced triceps brachii muscle hypertrophy could increase the muscle moment arm, but its impact can be small or negligible.
Norihide Sugisaki is with the Center for Environment, Health and Field Sciences, Chiba University, Kashiwa-no-ha, Kashiwa, Chiba, Japan. Taku Wakahara is with the Faculty of Health and Sports Science, Doshisha University, Tatara Miyakodani, Kyotanabe City, Kyoto, Japan. Koichiro Murata is with the Department of Human Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido, Japan. Naokazu Miyamoto, Hiroaki Kanehisa, and Tetsuo Fukunaga are with the Department of Sports and Life Science, National Institute of Fitness and Sports in Kanoya, Kanoya, Kagoshima, Japan. Yasuo Kawakami is with the Faculty of Sport Sciences, Waseda University, Tokorozawa, Saitama, Japan.