Power loss is greater in old men than young men during fast plantar flexion contractions
Power loss is greater in old men than young men during fast plantar flexion contractions
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DOI：
10.1152/japplphysiol.00335.2010
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发表时间：
2010-11-01
影响因子：
3.3
通讯作者：
Rice, Charles L.
中科院分区：
文献类型：
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作者：
Dalton, Brian H.;Power, Geoffrey A.;Rice, Charles L.
目前尚不清楚在人类衰老过程中，健康的老年人(70岁)与年轻人相比，疲劳性是更强、更弱还是相同。已报道的不同结果可能与疲劳的任务依赖性以及探索非等长收缩功能和衰老的研究数量有限有关。本研究的目的是采用等长和动态测量方法，测定10名青年男子(24岁)和10名老年男子(78岁)的小腿三头肌快速缩短收缩对其疲劳能力的影响。受试者在20%最大自愿等长收缩(MVC)的恒定负荷下进行了50次最大速度相关的足底屈曲。在基线、疲劳任务期间和之后测试等长抽动特性和MVC。自发性激活在老年人和年轻人之间是相似的(类似于98%)，并且不会因疲劳而改变。老年人的等长MVC扭矩比年轻人低26%(P<；0.01)，最大缩短速度慢18%(P<；0.01)。因此，老年人的峰值功率降低了38%(P<；0.01)。在任务结束时，老年人的MVC扭矩保持不变(P=0.15)，但年轻人的MVC扭矩下降了21%(P<；0.01)。在任务终止时，老年人的抽动半松弛时间延长了26%(P<；0.01)，而年轻人的收缩半松弛时间没有变化(P=0.10)。在任务终止时，老年人和年轻人的峰值功率分别降低了24%和17%(P<；0.01)。尽管等长MVC扭矩产生的维持性更好，但在以不受限制的速度进行快速动态训练时，老年人较弱且收缩较慢的小腿三头肌比年轻人更容易疲劳。
It is unclear during human aging whether healthy older adults (>70 yr old) experience greater, lesser, or the same fatigability compared with younger adults. The reported disparate findings may be related to the task-dependent nature of fatigue and the limited number of studies exploring nonisometric contractile function and aging. The purpose here was to determine the effects of fast shortening contractions on the fatigability of the triceps surae in 10 young (similar to 24 yr old) and 10 old (similar to 78 yr old) men using isometric and dynamic measures. Participants performed 50 maximal velocity-dependent plantar flexions at a constant load of 20% maximal voluntary isometric contraction (MVC). Isometric twitch properties and MVCs were tested at baseline and during and following the fatigue task. Voluntary activation was similar between the old and young (similar to 98%) and was unaltered with fatigue. The old had 26% lower (P < 0.01) isometric MVC torque and 18% slower (P < 0.01) maximal shortening velocity than the young. Hence, peak power was 38% lower in the old (P < 0.01). At task termination, MVC torque was maintained in the old (P = 0.15) but decreased by 21% in the young (P < 0.01). Twitch half-relaxation time was lengthened in the old at task termination by 26% (P < 0.01) but unchanged in the young (P = 0.10). Peak power was reduced by 24% and 17% at task termination in the old and young, respectively (P < 0.01). Despite a better maintenance in isometric MVC torque production, the weaker and slower contracting triceps surae of the old was more fatigable than the young during fast dynamic efforts with an unconstrained velocity.