Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma, USA.
J Strength Cond Res. 2012 Mar;26(3):633-40. doi: 10.1519/JSC.0b013e3182474296.
The purpose of this study was to examine the strength, electromyographic (EMG), and mechanomyographic (MMG) responses after workouts designed to elicit fatigue and muscle damage vs. only fatigue. Thirteen men (mean ± SD age = 23.7 ± 2.2 years) performed 6 sets of 10 maximal concentric isokinetic (CONexercise) or eccentric isokinetic (ECCexercise) muscle actions of the dominant forearm flexors on 2 separate days. Before (PRE) and after (POST) these workouts, peak torque (PT), surface EMG, and MMG signals were measured during maximal concentric isokinetic, eccentric isokinetic, and isometric muscle actions of the forearm flexors. The subjects also visited the laboratory for a control (CTL) visit with quiet resting between the PRE and POST measurements, rather than performing the CONexercise or ECCexercise. The results showed that there were significant 26 and 25% decreases in PT after the CONexercise and ECCexercise, respectively, and these decreases were statistically equivalent for the concentric, eccentric, and isometric muscle actions. There were also 19 and 23% reductions in normalized EMG amplitude after the CONexercise and ECCexercise, respectively, but no changes in EMG mean frequency (MNF), MMG amplitude, or MMG MNF. These findings demonstrated a neural component(s) to the strength decrement after CONexercise and ECCexercise. It is possible that after these 2 types of exercise, activation of free nerve endings that are sensitive to muscle damage and pH changes resulted in inhibition of alpha motor neurons, causing decreased muscle activation and torque. These findings suggest that training programs designed to minimize strength loss during competition should consider the fact that at least some of this loss is because of neural factors.
本研究的目的是检验与仅疲劳相比，旨在引起疲劳和肌肉损伤的锻炼后的强度、肌电图（EMG）和肌动描记图（MMG）反应。13 名男性（平均±标准差年龄=23.7±2.2 岁）在 2 天内分别进行了 6 组 10 次最大向心等速（CONexercise）或离心等速（ECCexercise）的优势前臂屈肌运动。在这些锻炼前后（PRE 和 POST），在最大向心等速、离心等速和前臂屈肌等长肌肉运动期间测量了峰值扭矩（PT）、表面 EMG 和 MMG 信号。受试者还在实验室进行了控制（CTL）访问，在 PRE 和 POST 测量之间保持安静休息，而不是进行 CONexercise 或 ECCexercise。结果表明，CONexercise 和 ECCexercise 后分别出现了 26%和 25%的 PT 显著下降，这两种下降在向心、离心和等长肌肉运动中具有统计学等效性。CONexercise 和 ECCexercise 后分别出现了 19%和 23%的 EMG 归一化幅度减少，但 EMG 平均频率（MNF）、MMG 幅度或 MMG MNF 没有变化。这些发现表明，CONexercise 和 ECCexercise 后力量下降存在神经成分。在这两种运动之后，可能由于对肌肉损伤和 pH 变化敏感的游离神经末梢的激活导致α运动神经元抑制，从而导致肌肉激活和扭矩减少。这些发现表明，旨在最大限度减少比赛期间力量损失的训练计划应考虑到这种损失至少部分是由于神经因素造成的事实。
