The aim was to investigate if the method of normalizing surface electromyography (sEMG) can change results on sex differences in the muscular activation of the shoulder girdle muscles during a simulated work task. sEMG was recorded in 36 asymptomatic participants (17 females, 19 males) from four parts of trapezius and from serratus anterior muscles during a simulated work task. Four normalization methods, one involving maximal voluntary contractions (MVCs) and three involving submaximal voluntary contractions were applied. Sex differences in absolute and normalized amplitude of sEMG were analyzed. The normalization method had a significant influence on the observed sex differences. Females only showed higher sEMG amplitude than males when the sEMGs were normalized to MVC and to a submaximal contraction based on 20% of MVC for the upper trapezius (acromial fibers). Researchers and practitioners should be aware of the impact of the sEMG normalization method in sex differences investigation.

中文翻译：

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在模拟工作任务期间，sEMG归一化变化是否由于性别差异导致肩带肌肉的激活？

目的是研究标准化表面肌电图（sEMG）的方法是否可以在模拟工作任务期间改变性别差异对肩带肌肉的肌肉激活的影响。在模拟工作任务期间，从斜方肌的四个部位和前锯肌的36名无症状参与者（17名女性，19名男性）中记录了sEMG。应用了四种归一化方法，一种涉及最大自愿收缩（MVC），三种涉及次最大自愿收缩。分析了sEMG的绝对幅度和归一化幅度的性别差异。标准化方法对观察到的性别差异有重大影响。当将sEMGs归一化为MVC并基于上斜方肌（肩峰纤维）的MVC的20％收缩至次最大收缩时，女性仅显示出比男性更高的sEMG振幅。研究人员和从业人员应意识到sEMG标准化方法在性别差异调查中的影响。