Motor unit firing rates and contractile properties in tibialis anterior of young and old men
Motor unit firing rates and contractile properties in tibialis anterior of young and old men
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DOI：
10.1152/jappl.1999.87.2.843
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发表时间：
1999-08-01
影响因子：
3.3
通讯作者：
Vandervoort, AA
中科院分区：
文献类型：
--
作者：
Connelly, DM;Rice, CL;Vandervoort, AA
通过比较6名年轻人（20.8 ± 0.8岁）和6名老年人（82.0 ± 1.7岁）的结果，研究了年龄对胫骨前肌运动神经元放电率和肌肉收缩特性的影响。对于每个受试者，在2周的时间内从重复测试中收集数据。收缩试验包括最大自主收缩（MVC）与抽搐内插和刺激抽搐收缩。老年人的MVC扭矩比年轻人低26%（P < 0.01），但激活百分比没有差异（分别为99.1%和99.3%）。老年人的抽搐收缩持续时间比青年人长23%（P < 0.01）。在10、25、50、75和100%MVC的一系列重复的短暂稳态收缩期间，记录运动单位放电率。在每个受试者组中进行的950个运动单位训练的结果表明，在所有相对扭矩水平下，老年受试者的平均放电率低30-35%（P < 0.01）。年轻和老年受试者在10%、50%和MVC扭矩下的平均放电率与其相应的平均抽搐收缩持续时间之间的比较产生了一系列中度到高度的相关性（r = -0.67至-0.84）。较低的放电率与老年人肌肉中较长的抽搐收缩持续时间相匹配，而相对较高的放电率与年轻人肌肉中较短的收缩时间相匹配，间接支持了神经肌肉年龄相关的重塑原理。
The effects of aging on motoneuron firing rates and muscle contractile properties were studied in tibialis anterior muscle by comparing results from six young (20.8 +/- 0.8 yr) and six old men (82.0 +/- 1.7 yr). For each subject, data were collected from repeated tests over a 2-wk period. Contractile tests included maximal voluntary contraction (MVC) with twitch interpolation and stimulated twitch contractions. The old men had 26% lower MVC torque (P < 0.01) than did the young men, but percent activation was not different (99.1 and 99.3%, respectively). Twitch contraction durations were 23% longer (P < 0.01) in the old compared with the young men. During a series of repeated brief steady-state contractions at 10, 25, 50, 75, and 100% MVC, motor unit firing rates were recorded. Results from similar to 950 motor unit trains in each subject group indicated that at all relative torque levels mean firing rates were 30-35% lower (P < 0.01) in the old subjects. Comparisons between young and old subjects' mean firing rates at each of 10%, 50%, and MVC torques and their corresponding mean twitch contraction duration yielded a range of moderate-to-high correlations (r = -0.67 to -0.84). That lower firing rates were matched to longer twitch contraction durations in the muscle of old men, and relatively higher firing rates were matched with shorter contraction times from the young men, indirectly supports the neuromuscular age-related remodeling principle.