In vivo physiological cross-sectional area and specific force are reduced in the gastrocnemius of elderly men
In vivo physiological cross-sectional area and specific force are reduced in the gastrocnemius of elderly men
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DOI：
10.1152/japplphysiol.01186.2004
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发表时间：
2005-09-01
影响因子：
3.3
通讯作者：
Narici, MV
中科院分区：
文献类型：
--
作者：
Morse, CI;Thom, JM;Narici, MV
肌肉减少症和肌肉无力是众所周知的衰老后果。本研究的目的是确定肌束力（Ff）的下降是否可以完全由肌肉萎缩引起。对一组73.8岁的老年男性[EM，年龄100岁]的腓肠肌（GL）外侧头的在体生理横截面积（PCSA）和比力（Ff/PCSA）进行了评估（SD 3.5），身高173.4 cm（SD 4.4），体重78.4 kg（SD 8.3）;平均值（SD）1，用于一组年轻男性[YM，年龄25.3岁（SD 4.4），身高176.4 cm（SD 7.7），体重79.1 kg（SD 11.9）]的比较。使用磁共振成像评估GL肌肉体积（ACL）和跟腱力臂长度。采用B型超声测量跖屈肌等长最大自主收缩时的羽状角和纤维束长度。PCSA估计为AUC/Lf。GL Ff的计算方法为：在最大双联体插值期间，将跟腱力除以0的余弦，并考虑拮抗剂激活水平（使用EMG评估）、跟腱力臂长度和跖屈肌组内GL的相对PCSA。EM组的跖屈肌自主激活率低于YM组（分别为86%和98%，P < 0.05）。与YM相比，EM的跖屈肌最大随意收缩力矩和Ff分别降低了47%和40%（P < 0.01）。EM组的平均动脉压和PCSA分别减小28%（P < 0.01）和16%（P < 0.05）。此外，在EM中，扇形角小12%，而在YM和EM之间的Lf没有显著差异。在考虑激动剂和拮抗剂激活差异后，EM的Ff/PCSA比YM低30%（P < 0.01）。这些发现表明，随着年龄的增长，肌肉力量的损失不仅可以解释为对肌肉的自愿驱动减少，而且主要是由内在肌肉力量的减少。这种现象可能是由于单纤维比张力的降低。
Sarcopenia and muscle weakness are well-known consequences of aging. The aim of the present study was to ascertain whether a decrease in fascicle force (Ff) could be accounted for entirely by muscle atrophy. In vivo physiological cross-sectional area (PCSA) and specific force (Ff/PCSA) of the lateral head of the gastrocnemius (GL) muscle were assessed in a group of elderly men [EM, aged 73.8 yr (SD 3.5), height 173.4 cm (SD 4.4), weight 78.4 kg (SD 8.3); means (SD)l and for comparison in a group of young men [YM, aged 25.3 yr (SD 4.4), height 176.4 cm (SD 7.7), weight 79.1 kg (SD 11.9)]. GL muscle volume (Vol) and Achilles tendon moment arm length were evaluated using magnetic resonance imaging. Pennation angle and fiber fascicle length (Lf) were measured using B-mode ultrasonography during isometric maximum voluntary contraction of the plantar flexors. PCSA was estimated as Vol/Lf. GL Ff was calculated by dividing Achilles tendon force by the cosine of 0, during the interpolation of a supramaximal doublet, and accounting for antagonist activation level (assessed using EMG), Achilles tendon moment arm length, and the relative PCSA of the GL within the plantar flexor group. Voluntary activation of the plantar flexors was lower in the EM than in the YM (86 vs. 98%, respectively, P < 0.05). Compared with the YM, plantar flexor maximal voluntary contraction torque and Ff of the EM were lower by 47 and 40%, respectively (P < 0.01). Both Vol and PCSA were smaller in the EM by 28% (P < 0.01) and 16% (P < 0.05), respectively. Also, pennation angle was 12% smaller in the EM, whereas there was no significant difference in Lf between the YM and EM. After accounting for differences in agonists and antagonists activation, the Ff/PCSA of the EM was 30% lower than that of the YM (P < 0.01). These findings demonstrate that the loss of muscle strength with aging may be explained not only by a reduction in voluntary drive to the muscle, but mostly by a decrease in intrinsic muscle force. This phenomenon may possibly be-due to a reduction in single-fiber specific tension.