Discipline of Physiology, School of Medical Sciences, The University of Adelaide, Adelaide, Australia.
J Neurophysiol. 2011 Mar;105(3):1225-35. doi: 10.1152/jn.00854.2010. Epub 2011 Jan 19.
The purpose of this study was to examine changes in motor unit activity in the biceps brachii muscle after an initial (Bout 1) and repeated (Bout 2) session of eccentric exercise separated by 1 wk. Eight subjects (aged 22 ± 2 yr) participated in experimental assessments of neuromuscular function obtained before, immediately after, 24 h after, and 7 days after each exercise bout. Each experimental session involved assessments of elbow-flexor force and biceps and triceps brachii electromyography during maximum voluntary isometric contractions (MVCs) and constant-force isometric contractions at five contraction intensities (5-50% MVC), along with indicators of muscle damage (muscle pain and passive tension). In addition, motor unit recordings were obtained before exercise, 7 days after Bout 1, and 24 h after Bout 2 to assess motor unit synchronization and recruitment thresholds. Following a single eccentric exercise session that elicited significant indicators of muscle damage, we found a 57% increase in motor unit synchronization 7 days later compared with before exercise, despite the recovery of maximal strength, soreness, and relaxed elbow-joint angle at this time. Furthermore, a second bout of the same eccentric exercise resulted in reduced indicators of muscle damage and a decline in the strength of motor unit synchronization (24 h after Bout 2) toward levels observed before both exercise sessions. In contrast, no changes in motor unit recruitment thresholds were observed 7 days after Bout 1 or 24 h after Bout 2 compared with before exercise. The increased motor unit synchronization 7 days after a single eccentric exercise session provides new evidence of changes in motor unit activity during the putative repair and regeneration phase following eccentric muscle damage.
本研究的目的是观察肱二头肌在初次（第 1 回合）和重复（第 2 回合）离心运动后，在 1 周的间隔内运动单位活动的变化。8 名受试者（年龄 22 ± 2 岁）参与了神经肌肉功能的实验评估，这些评估在每次运动回合之前、之后立即、24 小时后和 7 天后进行。每个实验回合包括在最大自主等长收缩（MVC）和五个收缩强度（5-50% MVC）的等长恒力收缩期间评估肘屈肌力量和肱二头肌和肱三头肌肌电图，以及肌肉损伤指标（肌肉疼痛和被动张力）。此外，在运动前、第 1 回合后 7 天和第 2 回合后 24 小时进行运动单位记录，以评估运动单位同步和募集阈值。在单次离心运动引起明显的肌肉损伤指标后，我们发现尽管此时最大力量、酸痛和放松的肘部关节角度已经恢复，但在第 7 天运动单位同步性增加了 57%。此外，相同的离心运动第二回合导致肌肉损伤指标减少，运动单位同步性强度下降（第 2 回合后 24 小时），接近两个运动回合前的水平。相比之下，与运动前相比，第 1 回合后 7 天或第 2 回合后 24 小时，运动单位募集阈值没有变化。单次离心运动后第 7 天运动单位同步性增加，为运动单位活动在离心性肌肉损伤后的修复和再生阶段提供了新的证据。
