2134/15147 Christopher I. Morse Christopher I. Morse Keith Tolfrey Keith Tolfrey Jeanette M. Thom Jeanette M. Thom Vasilios Vassilopoulos Vasilios Vassilopoulos Constantinos N. Maganaris Constantinos N. Maganaris Marco V. Narici Marco V. Narici Gastrocnemius muscle specific force in boys and men Loughborough University 2014 untagged Medical and Health Sciences not elsewhere classified 2014-07-08 12:49:57 Journal contribution https://repository.lboro.ac.uk/articles/journal_contribution/Gastrocnemius_muscle_specific_force_in_boys_and_men/9610772 The aim of this study was to assess whether the in vivo specific force and architectural characteristics of the lateral gastrocnemius (GL) muscle of early pubescent boys (n=11, age 10.9 ±0.3 yr, Tanner stage 2) differed from those of adult men (n=12, age 25.3 ±4.4 yr). Plantarflexor torque was 55% lower in the boys (77.4±21.4 Nm) compared with the adults (175.631.7 Nm,P0.01). Physiological cross-sectional area (PCSA), determined in vivo using ultrasonography and MRI, was 52% smaller in the boys (P0.01). No difference was found in pennation angle, or in the ratio of fascicle length (Lf)to muscle length between the boys and men. Moment arm length was 25% smaller in the boys (P0.01). Antagonist coactivation, assessed using surface EMG on the dorsiflexors, was not different between the boys and men (11.86.7% and 13.55.8%, respectively). Surprisingly, GL force normalized to PCSA (specific force) was significantly higher (21%) in the boys than in the men (13.12.0 vs. 15.92.7N/cm2,P0.05). This finding could not be explained by differences in moment arm length, muscle activation, or architecture, and other factors, such as tendinous characteristics and/or changes in moment arm length with contraction, may be held responsible. These observations warrant further investigation