Sex differences with aging in the fatigability of dynamic contractions.
Sex differences with aging in the fatigability of dynamic contractions.
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DOI：
10.1016/j.exger.2015.07.001
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发表时间：
2015-10
影响因子：
3.9
通讯作者：
Hunter SK
中科院分区：
文献类型：
--
作者：
Yoon T;Doyel R;Widule C;Hunter SK
本研究旨在探讨手肘屈肌在动态疲劳任务中疲劳性的性别差异及其机制。我们比较了18名年轻人（20.2±1岁：9名男性）和36名老年人（73.5±1岁：16名男性）在反复动态收缩（~60度/秒）期间和恢复期间手肘屈肌的疲劳性，负荷相当于最大随意等长收缩（MVIC）扭矩的20%，直至失败。经颅磁刺激（TMS）被用来评估脊髓上疲劳（增加叠加抽搐，SIT）和肌肉放松的峰值速率。男性的失败时间短于女性（分别为6.1±2.1 vs. 9.7±5.5 min; P=0.02），年轻人和老年人之间无差异（分别为7.2±2.9 vs. 8.4±5.2 min，P=0.45），无相互作用（P>0.05）。年轻人和老年人的峰值松弛率与疲劳性的相对下降相似（P=0.11），但男性比女性更大（P=0.046）。所有组的椎上疲劳均增加，并与失败时间相关（P<0.05）。然而，回归分析表明，失效时间最好通过峰值松弛率（基线值和疲劳性减缓）预测（r2=0.55）。限速收缩机制（如兴奋-收缩耦合）负责增加疲劳性的手肘屈肌的男性相比，女性的动态疲劳任务的角速度慢，这种性别差异保持与老化。相对于等长疲劳收缩通常观察到的情况，男女在动态任务疲劳性方面的年龄差异都有所减少。
This study determined the sex difference with aging in fatigability of the elbow flexor muscles during a dynamic fatiguing task, and explored the associated mechanisms. We compared fatigability of the elbow flexor muscles in 18 young (20.2±1 years: 9 men) and 36 old adults (73.5±1 years: 16 men) during and in recovery from repeated dynamic contractions (~60 deg/s) with a load equivalent to 20% of maximal voluntary isometric contraction (MVIC) torque until failure. Transcranial magnetic stimulation (TMS) was used to assess supraspinal fatigue (an increase in the superimposed twitch, SIT) and the peak rate of muscle relaxation. Time to failure was briefer for the men than the women (6.1±2.1 vs. 9.7±5.5 min, respectively; P=0.02) with no difference between young and old adults (7.2±2.9 vs. 8.4±5.2 min, respectively, P=0.45) and no interaction (P>0.05). The relative decline in peak relaxation rate with fatigability was similar for young and old adults (P=0.11), but greater for men than women (P=0.046). Supraspinal fatigue increased for all groups and was associated with the time to failure (P<0.05). Regression analysis however, indicated that the time to failure was best predicted by the peak relaxation rate (baseline values and slowing with fatigability) (r2=0.55). Rate-limiting contractile mechanisms (e.g. excitation-contraction coupling) were responsible for the increased fatigability of the elbow flexors of men compared with women for a dynamic fatiguing task of slow angular velocity, and this sex difference was maintained with aging. The age difference in fatigability for the dynamic task was diminished for both sexes relative to what is typically observed with isometric fatiguing contractions.