Baudry Stéphane, Klass Malgorzata, Pasquet Benjamin, Duchateau Jacques
Laboratory of Applied Biology, Université Libre de Bruxelles, 28 avenue P. Héger, CP 168, 1000 Brussels, Belgium.
Eur J Appl Physiol. 2007 Jul;100(5):515-25. doi: 10.1007/s00421-006-0206-9. Epub 2006 May 23.
This study compares the fatigability of the ankle dorsiflexors during five sets of 30 maximal concentric and eccentric contractions in young and elderly adults. The torque produced by the ankle dorsiflexors and the average surface electromyogram (aEMG) of the tibialis anterior were continuously recorded. The contribution of central and peripheral mechanisms to muscle fatigue was tested before, after each set of contractions, and during a 30 min recovery period by the superimposed electrical stimulation method. The compound muscle action potential (M-wave), the mechanical response to single (twitch) and paired (doublet) stimulation, and the postactivation potentiation were also recorded. Compared with young subjects, elderly adults exhibited a greater loss of torque for concentric (50.2 vs. 40.9%; P<0.05) and eccentric (42.1 vs. 27.1%; P < 0.01) contractions. Although young subjects showed a lesser decrease in torque during the eccentric compared with concentric contractions, elderly adults experienced similar fatigability for the two types of contractions despite a comparable depression in the EMG activity of both groups and contraction types (10-20%). As tested by the interpolated-twitch method and aEMG/M-wave ratio, voluntary activation was not altered during either type of contraction or for either age group. During the two fatigue tasks, only elderly adults experienced a decrease in M-wave area (26.4-35.4%; P < 0.05). All together, our results suggest that the fatigue exhibited by both young and elderly adults during maximal concentric and eccentric contractions mainly involved peripheral alterations and that elderly adults may also have experienced a decline in neuromuscular propagation.
本研究比较了年轻人和老年人在进行五组每组30次最大等长收缩和离心收缩时踝关节背屈肌的易疲劳性。连续记录踝关节背屈肌产生的扭矩以及胫前肌的平均表面肌电图（aEMG）。通过叠加电刺激法在每组收缩前、收缩后以及30分钟恢复期间测试中枢和外周机制对肌肉疲劳的影响。还记录了复合肌肉动作电位（M波）、对单次（单收缩）和配对（双收缩）刺激的机械反应以及激活后增强。与年轻受试者相比，老年人在进行向心收缩（50.2%对40.9%；P<0.05）和离心收缩（42.1%对27.1%；P<0.01）时扭矩损失更大。尽管年轻受试者在离心收缩期间扭矩下降幅度小于向心收缩，但两组在两种收缩类型中的肌电图活动均有相当程度的降低（10 - 20%），老年人在这两种收缩类型中的疲劳程度相似。通过内插单收缩法和aEMG/M波比值测试发现，在任何一种收缩类型中，两个年龄组的自愿激活均未改变。在两项疲劳任务中，只有老年人的M波面积减小（26.4 - 35.4%；P<0.05）。总之，我们的结果表明，年轻人和老年人在最大等长收缩和离心收缩过程中表现出的疲劳主要涉及外周改变，并且老年人可能还经历了神经肌肉传导的下降。
