title: Influence of muscle hypertrophy on the moment arm of the triceps brachii muscle.
abstract: Although the moment arm of the triceps brachii muscle has been shown to be associated with the muscle's anatomical cross-sectional 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.
authors.affiliation: Center for Environment, Health and Field Sciences, Chiba University, Kashiwa-no-ha, Kashiwa, Chiba, Japan.
authors.forename: Norihide
authors.initials: N
authors.lastname: Sugisaki
authors.forename: Taku
authors.initials: T
authors.lastname: Wakahara
authors.forename: Koichiro
authors.initials: K
authors.lastname: Murata
authors.forename: Naokazu
authors.initials: N
authors.lastname: Miyamoto
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawakami
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kanehisa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Fukunaga
mesh_terms: D000293:Adolescent; D004551:Elbow Joint / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D006984:Hypertrophy / Q000503:physiopathology; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D056740:Olecranon Process / Q000033:anatomy & histology*; D009929:Organ Size / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology; D015203:Reproducibility of Results; D055070:Resistance Training / Q000379:methods*; D012680:Sensitivity and Specificity; D019415:Torque; D016896:Treatment Outcome