Thom Jeanette M, Morse Chris I, Birch Karen M, Narici Marco V
Institute for Biophysical and Clinical Research into Human Movement (IRM), Manchester Metropolitan University, Alsager Campus, Hassall Road, Alsager, Cheshire, ST7 2HL, UK.
Eur J Appl Physiol. 2007 Jul;100(5):613-9. doi: 10.1007/s00421-007-0481-0. Epub 2007 May 26.
This study investigated the contribution of muscle architecture to the differences in the torque-velocity and power-velocity relationships between older (OM n = 9, aged 69-82 years) and younger men (YM n = 15, aged 19-35 years). Plantarflexors' (PF) maximal isometric and concentric torques were recorded at 0.87, 1.75, 2.62, 3.49 and 4.36 rad s(-1). Physiological cross-sectional area (PCSA) was calculated as the ratio of muscle volume (determined by magnetic resonance imaging) to muscle fascicle length (Lf, measured by ultrasonography). GM PCSA and Lf of the OM were, respectively, 14.3% (P < 0.05) and 19.3% (P < 0.05) smaller than of the YM. In the OM, GM maximum isometric torque and maximum contraction velocity (Vmax), estimated from Hill's equation were, respectively, 48.5 and 38.2% lower (P < 0.001) than in the YM. At all contraction velocities, the OM produced less torque than the YM (46.3% of YM at 0.87 rad s(-1) to 14.7% at 4.36 rad s(-1), P < 0.001). Peak power (PP) of the OM was 80% lower than that of the YM and normalisation of PP to muscle volume only reduced this difference by 10%. Normalisation of torque to PCSA reduced, but did not eliminate, differences in torque between YM and OM (9.6%) and differences in torque/PCSA increased with contraction velocity (P < 0.05). After normalisation of velocity to Lf, the difference in Vmax between the OM and the YM was reduced to 15.9%. Thus, although muscle architecture contributes significantly to the differences in the torque- and power-velocity properties of OM and YM, other contractile factors, intrinsic to the muscle, seem to play a role. It is noteworthy that the deficit in PP between OM and YM is far greater than that of muscle torque, even after normalisation of PP to muscle volume. This finding likely plays an important role in the loss of mobility in old age.
本研究调查了肌肉结构对老年男性（OM，n = 9，年龄69 - 82岁）和年轻男性（YM，n = 15，年龄19 - 35岁）之间扭矩 - 速度关系及功率 - 速度关系差异的影响。在0.87、1.75、2.62、3.49和4.36弧度·秒⁻¹时记录了跖屈肌（PF）的最大等长扭矩和向心扭矩。生理横截面积（PCSA）通过肌肉体积（由磁共振成像确定）与肌肉肌束长度（Lf，由超声测量）的比值计算得出。老年男性的腓肠肌内侧头PCSA和Lf分别比年轻男性小14.3%（P < 0.05）和19.3%（P < 0.05）。在老年男性中，根据希尔方程估算的腓肠肌内侧头最大等长扭矩和最大收缩速度（Vmax）分别比年轻男性低48.5%和38.2%（P < 0.001）。在所有收缩速度下，老年男性产生的扭矩均低于年轻男性（在0.87弧度·秒⁻¹时为年轻男性的46.3%，在4.36弧度·秒⁻¹时为14.7%，P < 0.001）。老年男性的峰值功率（PP）比年轻男性低80%，将PP归一化至肌肉体积仅使这种差异减少了10%。将扭矩归一化至PCSA减少了但未消除年轻男性和老年男性之间的扭矩差异（9.6%），并且扭矩/PCSA差异随收缩速度增加（P < 0.05）。在将速度归一化至Lf后，老年男性和年轻男性之间Vmax的差异降至15.9%。因此，尽管肌肉结构对老年男性和年轻男性的扭矩及功率 - 速度特性差异有显著贡献，但肌肉内在的其他收缩因素似乎也发挥了作用。值得注意的是，即使将PP归一化至肌肉体积，老年男性和年轻男性之间PP的 deficit仍远大于肌肉扭矩的 deficit。这一发现可能在老年人活动能力丧失中起重要作用。
