ACUTE EFFECT OF LOW-POWER LASER IN FATIGUE OF BICEPS BRACHII OF VOLLEYBALL ATHLETES

ABSTRACT Introduction: Low-power laser therapy has among its aims to aid the recovery of biological tissues, attenuating the effects of muscle fatigue and contributing to the improvement of performance in athletes. Methodological aspects still limit the conclusions of the acute effect of laser therapy on muscular performance. Objective: To verify the acute effect of low-power therapeutic laser in the induced fatigue in biceps brachii of volleyball athletes. Methods: This was a randomized double-blind study, approved by Institutional Review Board of UNESP, Marília. Nineteen volleyball athletes of both sexes participated in this study. Electromyographic data were collected from the biceps brachii muscle in isometric exercise of the elbow flexion before and after the application of the therapeutic laser. A dumbbell with 75% of the force peak, obtained by a load cell, was used for the fatigue protocol. The volunteers then underwent laser (active or placebo) application on six points of the biceps brachii muscle. The EMG data were analyzed in the frequency domain using the Myosystem ® software. The distribution of normality was verified by the Shapiro-Wilk test, and repeated measures ANOVA (split plot) was used to test the interaction between time and group. Results: No significant interaction between group and time was observed for any analyzes variables, indicating that the irradiated group did not show advantages over the placebo group. Conclusion: After the proposed fatigue protocol, a single low-power laser application was not sufficient to produce positive effects on strength performance and on the electromyographic signal of the biceps brachii muscle of volleyball athletes.

摘要：
引言：低功率激光疗法（low-power laser therapy）的核心目标之一包括辅助生物组织修复、缓解肌肉疲劳，以及提升运动员运动表现。当前方法学层面的局限仍制约了激光疗法对肌肉性能急性效应相关研究结论的可靠性。
研究目的：验证低功率治疗性激光对排球运动员肱二头肌疲劳诱导状态下的急性效应。
研究方法：本研究为随机双盲试验，经巴西圣保罗州立大学（UNESP）马里利亚校区伦理审查委员会（Institutional Review Board）批准。本研究共纳入19名男女排球运动员。在治疗性激光照射前后，采集受试者肱二头肌在肘关节屈曲等长收缩过程中的肌电数据（electromyographic data, EMG）。本研究通过负荷传感器测得受试者的峰值力量，并以其75%作为哑铃负荷，实施疲劳诱导方案。随后，受试者接受肱二头肌6个位点的激光照射，分为治疗组与安慰剂组（placebo group）。采用Myosystem®软件对肌电数据进行频域分析；通过夏皮罗-威尔克检验（Shapiro-Wilk test）验证数据的正态分布特征，并采用裂区设计重复测量方差分析（repeated measures ANOVA, split plot）检验时间与分组的交互效应。
研究结果：所有分析变量均未观测到分组与时间间存在显著交互效应，提示激光照射组未表现出优于安慰剂组的效果。
研究结论：在完成既定疲劳诱导方案后，单次低功率激光照射无法对排球运动员肱二头肌的力量性能及肌电信号产生积极影响。