Leong B, Kamen G, Patten C, Burke J R
Department of Exercise Science, University of Massachusetts at Amherst, 01003, USA.
Med Sci Sports Exerc. 1999 Nov;31(11):1638-44. doi: 10.1097/00005768-199911000-00022.
Although the existence of "neural factors" is regularly cited as an important contributor to muscular strength, we have little specific knowledge regarding the existence of such neural factors or how they contribute to the expression of muscular force.
The present investigation sought to assess maximal motor unit discharge rates in older, highly resistance-trained adults to determine whether maximal motor unit discharge rates might be one such neural contributor to maximal strength production.
Subjects consisted of seven well-trained older weight lifters (ages 67-79 yr) and five untrained age-matched older adults. While subjects performed 50 and 100% maximal voluntary knee extensor contractions (MVC), recordings from groups of motor units were obtained from the rectus femoris muscle by using an indwelling electrode. Off-line analysis was performed to identify individual motor unit firing occurrences and to compute maximal motor unit discharge rates.
As expected, knee extension strength in the trained weight lifters (367.0 +/- 72.0 N) was significantly greater than that in the control subjects (299.9 +/- 35.9 N; P < 0.05). Motor unit discharge rates were similar in the two subject groups at the 50% MVC force level (P > 0.05), but maximal (100% MVC) motor unit discharge rate in the weight lifters (23.8 +/- 7.71 pps) was significantly greater than that in the age-matched controls (19.1 +/- 6.29 pps; P < 0.05).
Motor unit discharge rates may comprise an important neural factor contributing to maximal strength in older adults.
尽管“神经因素”的存在常被认为是肌肉力量的一个重要促成因素，但我们对这类神经因素的存在情况或它们如何促成肌肉力量的表达知之甚少。
本研究旨在评估年龄较大、经过高强度抗阻训练的成年人的最大运动单位放电率，以确定最大运动单位放电率是否可能是最大力量产生的此类神经促成因素之一。
受试者包括7名训练有素的老年举重运动员（年龄67 - 79岁）和5名年龄匹配的未经训练的老年人。当受试者进行50%和100%最大自主膝关节伸展收缩（MVC）时，通过植入电极从股直肌获取运动单位组的记录。进行离线分析以识别单个运动单位放电事件并计算最大运动单位放电率。
正如预期，训练有素的举重运动员的膝关节伸展力量（367.0±72.0 N）显著大于对照组受试者（299.9±35.9 N；P < 0.05）。在50%MVC力量水平时，两组受试者的运动单位放电率相似（P > 0.05），但举重运动员的最大（100%MVC）运动单位放电率（23.8±7.71次/秒）显著高于年龄匹配的对照组（19.1±6.29次/秒；P < 0.05）。
运动单位放电率可能是促成老年人最大力量的一个重要神经因素。
