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J Appl Physiol 104: 469-474, 2008. First published December 20, 2007; doi:10.1152/japplphysiol.00697.2007
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Gastrocnemius muscle specific force in boys and men

Christopher I. Morse, Keith Tolfrey, Jeanette M. Thom, Vasilios Vassilopoulos, Constantinos N. Maganaris, and Marco V. Narici

Institute for Biophysical and Clinical Research into Human Movement and Health (IRM), Manchester Metropolitan University, Alsager, Cheshire, United Kingdom

Submitted 29 June 2007 ; accepted in final form 10 December 2007

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 N·m) compared with the adults (175.6 ± 31.7 N·m, P < 0.01). Physiological cross-sectional area (PCSA), determined in vivo using ultrasonography and MRI, was 52% smaller in the boys (P < 0.01). 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 (P < 0.01). Antagonist coactivation, assessed using surface EMG on the dorsiflexors, was not different between the boys and men (11.8 ± 6.7% and 13.5 ± 5.8%, respectively). Surprisingly, GL force normalized to PCSA (specific force) was significantly higher (21%) in the boys than in the men (13.1 ± 2.0 vs. 15.9 ± 2.7 N/cm2, P < 0.05). 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.

pennation angle; fascicle length; muscle architecture


Address for reprint requests and other correspondence: M. Narici, Institute for Biophysical Research into Human Movement and Health, Manchester Metropolitan Univ., Alsager Campus, Hassall Rd., Alsager, Cheshire ST7 2HL, UK (e-mail: m.narici{at}mmu.ac.uk)






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