title: Gastrocnemius muscle specific force in boys and men.
abstract: 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 x m) compared with the adults (175.6 +/- 31.7 N x 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 (L(f)) 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/cm(2), 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.
authors: Institute for Biophysical Research into Human Movement and Health, Manchester Metropolitan Univ., Alsager Campus, Hassall Rd., Alsager, Cheshire ST7 2HL, UK.
authors: Christopher I
authors: CI
authors: Morse
authors: Keith
authors: K
authors: Tolfrey
authors: Jeanette M
authors: JM
authors: Thom
authors: Vasilios
authors: V
authors: Vassilopoulos
authors: Constantinos N
authors: CN
authors: Maganaris
authors: Marco V
authors: MV
authors: Narici
mesh_terms: D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D002648:Child; D004576:Electromyography; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D009929:Organ Size; D011627:Puberty; D019415:Torque; D014463:Ultrasonography