Recovery from supraspinal fatigue is slowed in old adults after fatiguing maximal isometric contractions
Recovery from supraspinal fatigue is slowed in old adults after fatiguing maximal isometric contractions
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DOI：
10.1152/japplphysiol.01246.2007
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发表时间：
2008-10-01
影响因子：
3.3
通讯作者：
Taylor, Janet L.
中科院分区：
文献类型：
--
作者：
Hunter, Sandra K.;Todd, Gabrielle;Taylor, Janet L.
这项研究比较了脊柱上疲劳对老年人和年轻人肌肉疲劳的影响。采用经颅运动皮质磁刺激(TMS)技术，对17例青年(25.5+/-3.6岁；平均+/-SD)和7例老年人(73.0+/-3.3岁)肘屈肌最大自主收缩(MVC)时的自主活动进行了研究。受试者进行了一项疲劳任务，包括6个持续的MVC(22-S持续时间，隔开10个S)。年轻人的最大自愿扭矩(67+/-15%)比老年人(37+/-6%；P<；0.001)的下降幅度更大。在持续的MVC期间，TMS产生的扭矩(叠加的抽动)增量在年轻人和老年人中增加(P<；0.001)，但在持续收缩开始和恢复期间，老年人的增量更大(P<；0.05)。在持续收缩开始和恢复期间，老年人的自主激活较少(P=0.02)。在疲劳任务中，运动诱发电位面积随着年龄的增长类似地增加，但在恢复过程中，老年人比年轻人更大。在疲劳任务中，老年人的静默期延长较少。在疲劳任务结束时，年轻人肌肉纤维的峰值松弛速率比老年人下降得更多。年龄越大，耐力越强，这在很大程度上是由于肌肉内部机制的不同。然而，老年人从疲劳运动中恢复的能力受到损害，因为比年轻人更严重的是脊柱上的疲劳。
This study compared the contribution of supraspinal fatigue to muscle fatigue in old and young adults. Transcranial magnetic stimulation (TMS) of motor cortex was used to assess voluntary activation during maximal voluntary contractions (MVCs) of elbow flexor muscles in 17 young adults (25.5 +/- 3.6 yr; mean +/- SD) and 7 old adults (73.0 +/- 3.3 yr). Subjects performed a fatigue task involving six sustained MVCs (22-s duration, separated by 10 s). Young adults exhibited greater reductions in maximal voluntary torque (67 +/- 15% of baseline) than the old (37 +/- 6%; P < 0.001). Increments in torque (superimposed twitch) generated by TMS during sustained MVCs increased for the young and old (P < 0.001) but were larger for the old adults at the start of the sustained contractions and during recovery (P < 0.05). Voluntary activation was less for the old adults at the start of some sustained contractions and during recovery (P = 0.02). Motor-evoked potential area increased similarly with age during the fatiguing task but was greater for the old adults than young during recovery. Silent period duration lengthened less for the old adults during the fatigue task. At the end of the fatiguing task, peak relaxation rate of muscle fibers had declined more in the young than the old adults. The greater endurance with age is largely due to a difference in mechanisms located within the muscle. However, recovery from the fatiguing exercise is impaired for old adults because of greater supraspinal fatigue than in the young.