School of Kinesiology, Shanghai University of Sport, Shanghai 200438, China.
J Biomech. 2010 Feb 10;43(3):551-6. doi: 10.1016/j.jbiomech.2009.09.034. Epub 2009 Nov 28.
The aim of this work was to investigate the effects of age-related sarcopenia on the time and frequency domain properties of lower extremity muscles' electromyographic and mechanomyographic activities. Healthy elderly (n=10, 64.5+/-4.5yr) and young (n=10, 22.6+/-2.8yr) were recruited as participants. Participants' lean thigh volumes (LTV) and 1 RM (one repetition maximum) leg strength of quadriceps and maximum speed knee extension with different load levels (45%, 60% and 75% 1 RM) were recorded. The root mean square (RMS) and the mean frequency (MF) of the surface electromyography (EMG(RMS), EMG(MF)) and mechanomyography (MMG(RMS), MMG(MF)) signals were collected at vastus lateralis during concentric contraction with different intensity levels. Compared to the young, the elderly had significantly less LTV, absolute and relative maximal force, as well as absolute and relative maximal power (p<.05). EMG(MF) of the elderly and the young increased monotonically from 45% to 75% 1 RM testing conditions. While the MMG(RMS) of the young increased with testing intensities, the MMG(RMS) of the elderly increased only from 45% to 60% but leveled off from 60% to 75% 1 RM testing conditions. The results indicate the declines of muscle mass, force and power production capacity with aging. The observations could be explained by neuromuscular performance and change of MU activation patterns may result from age-related sarcopenia. Aging affected muscle power more than muscle strength, which could be due to fast fiber reduction. This is supported by our observations that the MMG(RMS) differences between the young and the elderly across all three intensity level where EMG(RMS) was only different at the greatest intensity. We suggest that MMG could be used as an important measurement in studying muscle contraction in age-related sarcopenia.
本研究旨在探讨与年龄相关的肌肉减少症对下肢肌肉肌电图和肌动图活动的时频域特性的影响。招募了健康的老年人（n=10，64.5±4.5 岁）和年轻人（n=10，22.6±2.8 岁）作为参与者。记录了参与者的瘦大腿体积（LTV）和 1 RM（最大重复次数）股四头肌力量，以及在不同负荷水平（45%、60%和 75% 1 RM）下最大速度的膝关节伸展速度。在等速收缩过程中，采集了股外侧肌表面肌电图（EMG(RMS)、EMG(MF)）和肌动图（MMG(RMS)、MMG(MF)）信号的均方根（RMS）和平均频率（MF）。与年轻人相比，老年人的 LTV、绝对和相对最大力量以及绝对和相对最大功率显著降低（p<.05）。老年人和年轻人的 EMG(MF)随着 1 RM 测试条件从 45%增加到 75%而单调增加。而年轻人的 MMG(RMS)随着测试强度的增加而增加，老年人的 MMG(RMS)仅从 45%增加到 60%，但从 60%增加到 75% 1 RM 测试条件时趋于平稳。研究结果表明，随着年龄的增长，肌肉质量、力量和力量产生能力下降。这些观察结果可以用神经肌肉性能来解释，而 MU 激活模式的变化可能是由于与年龄相关的肌肉减少症引起的。衰老对肌肉力量的影响大于肌肉力量，这可能是由于快纤维减少所致。这与我们的观察结果一致，即年轻人和老年人在所有三个强度水平下的 MMG(RMS)差异，而在最大强度下只有 EMG(RMS)不同。我们认为，肌动图可以作为研究与年龄相关的肌肉减少症中肌肉收缩的重要测量方法。
