School of Exercise and Nutrition Sciences, Faculty of Health, Queensland University of Technology (QUT), Brisbane, Australia.
Griffith University, Menzies Health Institute Queensland, The Hopkins Centre, Brisbane, Australia.
Mech Ageing Dev. 2022 Apr;203:111647. doi: 10.1016/j.mad.2022.111647. Epub 2022 Feb 23.
Nervous system maladaptation is linked to the loss of maximal strength and motor control with aging. Motor unit discharge rates are a critical determinant of force production; thus, lower discharge rates could be a mechanism underpinning maximal strength and motor control losses during aging. This meta-analysis summarized the findings of studies comparing motor unit discharge rates between young and older adults, and examined the effects of the selected muscle and contraction intensity on the magnitude of discharge rate difference between these two groups. Estimates from 29 studies, across a range of muscles and contraction intensities, were combined in a multilevel meta-analysis, to investigate whether discharge rates differed between young and older adults. Motor unit discharge rates were higher in younger than older adults, with a pooled standardized mean difference (SMD) of 0.66 (95%CI= 0.29-1.04). Contraction intensity had a significant effect on the pooled SMD, with a 1% increase in intensity associated with a 0.009 (95%CI= 0.003-0.015) change in the pooled SMD. These findings suggest that reductions in motor unit discharge rates, especially at higher contraction intensities, may be an important mechanism underpinning age-related losses in maximal force production.
神经系统适应不良与衰老导致的最大力量和运动控制丧失有关。运动单位放电率是力量产生的关键决定因素；因此，较低的放电率可能是导致衰老过程中最大力量和运动控制丧失的机制。这项荟萃分析总结了比较年轻人和老年人运动单位放电率的研究结果，并研究了所选肌肉和收缩强度对这两组之间放电率差异幅度的影响。对来自 29 项研究的估计值进行了多层次荟萃分析，以研究放电率是否在年轻人和老年人之间存在差异。年轻人的运动单位放电率高于老年人， pooled standardized mean difference (SMD) 为 0.66 (95%CI= 0.29-1.04)。收缩强度对 pooled SMD 有显著影响，强度增加 1%，pooled SMD 变化 0.009（95%CI= 0.003-0.015）。这些发现表明，运动单位放电率的降低，特别是在较高的收缩强度下，可能是导致最大力量产生与年龄相关的丧失的一个重要机制。
