老年人肌力流失与肌肉疲劳的肌动图研究

研究目的：探讨老年人肌力流失对肌肉质量、最大肌力与爆发力的影响，并以肌动图（MMG）来观察老年人股外肌在不同强度表现时运动单位的激活与老化对肌肉疲劳的影响。研究方法：受试者为老年组与年轻组各10位。受试者实施股四头肌最大等长收缩、最快速度不同强度（75％、60％、45％1RM）的伸膝动作及45％的疲劳测试，记录向心期不同强度的MMG讯号。研究结果：老年组的绝对／相对最大肌力与爆发力皆明显低于年轻组（P〈0．05），而相对最大爆发力比最大肌力下降的比例高达46．2％；各强度的MMG振幅与平均功率频率皆小于年轻组（P〈0．05），显示老年组的肌纤维以慢肌为主，并发现老年组75％强度时的MMG振幅下降，表示老年人因高负荷募集不到快肌所致；MMG中位频率则无年龄差异。研究结论：老年人在静、动态力量表现有肌力流失的现象，老化对爆发力影响远超过对肌力影响，MMG讯号反应肌肉收缩的力学活动。

Mechanomyographic Study on Age-related Sarcopenia and Muscular Fatigue

The purpose of this study was to investigate the effects of age-related sarcopenia on muscle mass,relative muscle strength/power in the lower limbs,and the responses of mechanomyography(MMG) on the activation patterns of motor units under leg extension muscle power in the elder people.Subjects are divided into elder and young groups.All subjects performed quadriceps maximal voluntary contraction(MVC) and fastest speed leg extension with different levels(75%,60%,45% 1RM),and 45% fatigue test to all-out.Absolute/relative maximal MVC(MVCmax),maximal power of 75%1RM(Pmax),different level MMG amplitudes and mean power frequency responses of vastus lateralis concentric contraction,and median frequency(mdfMMG) response to fatigue are compared between groups.Comparing to the young group,the elder group has significantly less absolute/relative MVCmax and Pmax(P<0.05),whereas relative Pmax(-72%) decreased more than MVCmax(-26.3) with 46.2%,the decreased 75% MMG amplitude are observed among the elder group due to failure recruitment of fast-twitch;No age difference in post-fatigue mdfMMG.The result shows that the declines of muscle mass,neuromuscular performance and changes of MU activation patterns may result from age-related sarcopenia and the age affects muscle power more than muscle strength.