Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec H2W 1S4, Canada; Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, Quebec H7V 1R2, Canada.
Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec H2W 1S4, Canada; Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, Quebec H7V 1R2, Canada.
Hum Mov Sci. 2023 Dec;92:103149. doi: 10.1016/j.humov.2023.103149. Epub 2023 Sep 22.
Previous studies have shown that the dominant arm is generally stronger and more resistant to fatigue. However, whether there are side differences in shoulder muscle activation during a fatiguing upper limb task, and whether this varies according to sex, is unknown. Thirty right-handed adults (15 females) were recruited to complete two sessions of an overhead repetitive fatiguing task (shoulder flexion between 90 and 135° at 1 Hz), performed in two separate sessions with their dominant arm (DA) and non-dominant arm (NDA) until exhaustion. Electromyographic (EMG) data was collected from 11 shoulder muscles of the moving arm, and their activation amplitude (RMS) and activation variability (SD) were assessed. Results show that time to exhaustion was not affected by arm or by sex. There were some main arm effects on EMG activity amplitude, with higher activity on the DA's pectoralis major (p < 0.001), and on the NDA's middle (p = 0.009) and posterior deltoid (p = 0.001) and infraspinatus (p < 0.001). The pectoralis major was affected by arm and fatigue mostly in males. Their DA's pectoralis major activity amplitude was higher, and the amplitude variability was lower, compared to the NDA, with both parameters showing fatigue-dependent decreases at the NDA only (arm x sex x fatigue: RMS: p = 0.007; SD: p = 0.001). As for females, the DA variability of their lower trapezius was smaller, and that of their subscapularis was higher, compared to the NDA (sex x arm, p = 0.028, p = 0.05). There was also more EMG variability on the supraspinatus' dominant side, and on the posterior deltoid and infraspinatus ND side. Results show an overhead shoulder flexion task dependency on pectoralis major control in males, and on lower trapezius and shoulder girdle stabilizers in females, which could be related to both sex- and gender-based factors. This knowledge can help identify side-specific injury risk factors due to overhead work in males and females, and help determine the appropriateness of implementing sex-specific workplace protocols, including alternating arms as fatigue compensatory and recovery strategies.
先前的研究表明，惯用手通常更强壮，更不易疲劳。然而，在进行上肢疲劳任务时，肩部肌肉的激活是否存在侧别差异，以及这种差异是否因性别而异，目前尚不清楚。
招募了 30 名右利手成年人（15 名女性），让他们分别用惯用手（DA）和非惯用手（NDA）完成两次重复的肩部过顶疲劳任务（90 到 135°的肩部屈伸，频率为 1Hz），直至力竭。对运动手臂的 11 块肩部肌肉进行肌电图（EMG）数据采集，并评估其激活幅度（RMS）和激活变异性（SD）。
结果表明，力竭时间不受手臂或性别的影响。EMG 活动幅度存在一些主要手臂效应，DA 的胸大肌活动更高（p < 0.001），NDA 的中三角肌（p = 0.009）、后三角肌（p = 0.001）和冈下肌（p < 0.001）也是如此。胸大肌主要受手臂和疲劳的影响，男性更为明显。与 NDA 相比，男性 DA 的胸大肌活动幅度更高，幅度变异性更低，且只有 NDA 的参数随疲劳而降低（手臂 x 性别 x 疲劳：RMS：p = 0.007；SD：p = 0.001）。而对于女性，与 NDA 相比，其 DA 的下斜方肌变异性更小，肩胛下肌变异性更大（性别 x 手臂，p = 0.028，p = 0.05）。此外，优势侧的冈上肌和三角肌后束以及非优势侧的三角肌后束和冈下肌的 EMG 变异性更大。
这些结果表明，在上肢过顶肩部屈伸任务中，男性依赖于胸大肌的控制，而女性依赖于下斜方肌和肩带稳定肌，这可能与性别和基于性别的因素有关。
这些知识有助于识别因上肢过顶工作导致的男性和女性的特定手臂损伤风险因素，并有助于确定实施基于性别的工作场所协议的适当性，包括交替手臂作为疲劳补偿和恢复策略。
