Department of Kinesiology and Physical Education, McGill University, Montreal, Quebec, Canada.
Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, Quebec, Canada.
PLoS One. 2020 Dec 18;15(12):e0244321. doi: 10.1371/journal.pone.0244321. eCollection 2020.
Women involved in repetitive, fatiguing, jobs develop more neck and/or shoulder musculoskeletal disorders than men. Sex differences in the pain response to exercise could contribute to the higher prevalence of neck/shoulder musculoskeletal disorders in women. The objective of this study was to assess sex differences in pain sensitivity following a fatiguing upper limb task. Relationships between measures of fatigue and of the sensitivity to nociceptive and to non-nociceptive stimulations were also explored.
Thirty healthy adults (15 women) performed a fatiguing repetitive pointing task with their dominant arm. Upper limb electromyography was recorded from the dominant upper trapezius, anterior deltoid and bicep brachii and from the contralateral tibialis anterior. Before and immediately after the repetitive pointing task, pressure pain and light touch sensitivity thresholds were measured over the same muscles.
Electromyographic signs of fatigue were observed only in the anterior deltoid and biceps brachii muscles. Pressure pain thresholds over both muscles increased slightly (effect size ≤ 0.34), but no changes occurred over the upper trapezius and the tibialis anterior. Light touch thresholds increased moderately to importantly after the repetitive pointing task over all four muscles (effect sizes = 0.58 to 0.87). No sex differences were observed in any sensory variable. Moreover, no or weak correlations (r = -0.27 to 0.39) were observed between electromyographical signs of fatigue, light touch threshold and pressure pain threshold variables.
We observed sex-independent effects of a repetitive upper limb task on the sensitivity to painful and to nonpainful stimuli. Moreover, the hypoalgesia induced by the repetitive pointing task was weak and localized, and did not directly correlate with the induced muscle fatigue. Results suggest that fatigue-related changes in the sensitivity to noxious and innocuous stimuli could not explain women's greater prevalence of neck/shoulder musculoskeletal disorders.
从事重复性、使人疲劳的工作的女性比男性更容易患上颈部和/或肩部肌肉骨骼疾病。运动引起的疼痛反应的性别差异可能导致女性颈部/肩部肌肉骨骼疾病的患病率更高。本研究的目的是评估疲劳上肢任务后疼痛敏感性的性别差异。还探讨了疲劳测量与伤害性和非伤害性刺激敏感性之间的关系。
30 名健康成年人（15 名女性）用优势手臂进行疲劳重复指向任务。从优势上肢斜方肌上部、三角肌前部和肱二头肌以及对侧胫骨前肌记录肌电图。在重复指向任务之前和之后，立即在相同的肌肉上测量压痛和轻触觉阈值。
仅在前三角肌和肱二头肌中观察到疲劳的肌电图迹象。两种肌肉的压痛阈值均略有增加（效应大小≤0.34），但斜方肌上部和胫骨前肌无变化。重复指向任务后，所有四块肌肉的轻触觉阈值均中度至显著增加（效应大小=0.58 至 0.87）。在任何感觉变量中均未观察到性别差异。此外，肌电图疲劳迹象、轻触觉阈值和压痛阈值变量之间观察到的相关性很弱或没有（r=-0.27 至 0.39）。
我们观察到重复性上肢任务对疼痛和非疼痛刺激敏感性的独立于性别的影响。此外，重复指向任务引起的痛觉减退是微弱和局部的，与诱导的肌肉疲劳没有直接相关性。结果表明，与疲劳相关的伤害性和无害性刺激敏感性变化不能解释女性颈部/肩部肌肉骨骼疾病患病率较高的原因。
