Power Geoffrey A, Allen Matti D, Gilmore Kevin J, Stashuk Daniel W, Doherty Timothy J, Hepple Russell T, Taivassalo Tanja, Rice Charles L
Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph Ontario, Canada;
School of Medicine and School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada.
J Appl Physiol (1985). 2016 Oct 1;121(4):1013-1020. doi: 10.1152/japplphysiol.00149.2016. Epub 2016 Mar 24.
Our group has shown a greater number of functioning motor units (MU) in a cohort of highly active older (∼65 yr) masters runners relative to age-matched controls. Because of the precipitous loss in the number of functioning MUs in the eighth and ninth decades of life it is unknown whether older world class octogenarian masters athletes (MA) would also have greater numbers of functioning MUs compared with age-matched controls. We measured MU numbers and neuromuscular transmission stability in the tibialis anterior of world champion MAs (∼80 yr) and compared the values with healthy age-matched controls (∼80 yr). Decomposition-enhanced spike-triggered averaging was used to collect surface and intramuscular electromyography signals during dorsiflexion at ∼25% of maximum voluntary isometric contraction. Near fiber (NF) MU potential analysis was used to assess neuromuscular transmission stability. For the MAs compared with age-matched controls, the amount of excitable muscle mass (compound muscle action potential) was 14% greater (P < 0.05), there was a trend (P = 0.07) toward a 27% smaller surface-detected MU potential representative of less collateral reinnervation, and 28% more functioning MUs (P < 0.05). Additionally, the MAs had greater MU neuromuscular stability than the controls, as indicated by lower NF jitter and jiggle values (P < 0.05). These results demonstrate that high-performing octogenarians better maintain neuromuscular stability of the MU and mitigate the loss of MUs associated with aging well into the later decades of life during which time the loss of muscle mass and strength becomes functionally relevant. Future studies may identify the concomitant roles genetics and exercise play in neuroprotection.
我们的研究小组发现，与年龄匹配的对照组相比，一群高活跃度的老年（约65岁）大师级跑步运动员拥有更多功能正常的运动单位（MU）。由于在人生的第八和第九个十年中，功能正常的运动单位数量会急剧减少，因此尚不清楚老年的世界级八旬大师级运动员（MA）与年龄匹配的对照组相比，是否也会有更多功能正常的运动单位。我们测量了世界冠军级大师级运动员（约80岁）胫前肌的运动单位数量和神经肌肉传递稳定性，并将这些值与健康的年龄匹配对照组（约80岁）进行比较。在最大自主等长收缩的约25%进行背屈时，使用分解增强的触发脉冲平均法来收集表面肌电图和肌内肌电图信号。采用近纤维（NF）运动单位电位分析来评估神经肌肉传递稳定性。与年龄匹配的对照组相比，大师级运动员的可兴奋肌肉质量（复合肌肉动作电位）高出14%（P<0.05），表面检测到的运动单位电位有减小27%的趋势（P=0.07），这代表着侧支神经再支配减少，且功能正常的运动单位多28%（P<0.05）。此外，大师级运动员的运动单位神经肌肉稳定性高于对照组，表现为较低的NF抖动和微颤值（P<0.05）。这些结果表明，高龄的优秀运动员能更好地维持运动单位的神经肌肉稳定性，并减轻与衰老相关的运动单位损失，直至生命的后几十年，此时肌肉质量和力量的损失在功能上变得至关重要。未来的研究可能会确定基因和运动在神经保护中所起的协同作用。
