Gastrocnemius muscle specific force in boys and men.
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.
Morse
Christopher I
CI
Institute for Biophysical Research into Human Movement and Health, Manchester Metropolitan Univ., Alsager Campus, Hassall Rd., Alsager, Cheshire ST7 2HL, UK.
Tolfrey
Keith
K
Thom
Jeanette M
JM
Vassilopoulos
Vasilios
V
Maganaris
Constantinos N
CN
Narici
Marco V
MV
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