Vafadar Amir K, Côté Julie N, Archambault Philippe S
School of Physical and Occupational Therapy, McGill University and Interdisciplinary Research Center in Rehabilitation (CRIR), 3654 Promenade Sir William Osler, Montreal, QC, H3G 1Y5, Canada.
Department of Kinesiology and Physical Education, McGill University and Interdisciplinary Research Center in Rehabilitation (CRIR), 475 Pine Avenue West, Montreal, QC, H2W 1S4, Canada.
BMC Musculoskelet Disord. 2015 Sep 30;16:273. doi: 10.1186/s12891-015-0731-y.
Work-related musculoskeletal disorders (WMSD) is the most expensive form of work disability. Female sex has been considered as an individual risk factor for the development of WMSD, specifically in the neck and shoulder region. One of the factors that might contribute to the higher injury rate in women is possible differences in neuromuscular control. Accordingly the purpose of this study was to estimate the effect of sex on shoulder joint position sense acuity (as a part of shoulder neuromuscular control) in healthy individuals.
Twenty-eight healthy participants, 14 females and 14 males were recruited for this study. To test position sense acuity, subjects were asked to flex their dominant shoulder to one of the three pre-defined angle ranges (low, mid and high-ranges) with eyes closed, hold their arm in that position for three seconds, go back to the starting position and then immediately replicate the same joint flexion angle, while the difference between the reproduced and original angle was taken as the measure of position sense error. The errors were measured using Vicon motion capture system. Subjects reproduced nine positions in total (3 ranges × 3 trials each).
Calculation of absolute repositioning error (magnitude of error) showed no significant difference between men and women (p-value ≥ 0.05). However, the analysis of the direction of error (constant error) showed a significant difference between the sexes, as women tended to mostly overestimate the target, whereas men tended to both overestimate and underestimate the target (p-value ≤ 0.01, observed power = 0.79). The results also showed that men had a significantly more variable error, indicating more variability in their position sense, compared to women (p-value ≤ 0.05, observed power = 0.78).
Differences observed in the constant JPS error suggest that men and women might use different neuromuscular control strategies in the upper limb. In addition, higher JPS variability observed in men might be one of the factors that could contribute to their lower rate of musculoskeletal disorders, compared to women.
The result of this study showed that shoulder position sense, as part of the neuromuscular control system, differs between men and women. This finding can help us better understand the reasons behind the higher rate of musculoskeletal disorders in women, especially in the working environments.
与工作相关的肌肉骨骼疾病（WMSD）是工作致残最昂贵的形式。女性被认为是发生WMSD的个体危险因素，特别是在颈部和肩部区域。可能导致女性受伤率较高的因素之一是神经肌肉控制方面的潜在差异。因此，本研究的目的是评估性别对健康个体肩关节位置觉敏锐度（作为肩部神经肌肉控制的一部分）的影响。
本研究招募了28名健康参与者，其中14名女性和14名男性。为了测试位置觉敏锐度，要求受试者闭上眼睛将优势肩屈曲到三个预先定义的角度范围（低、中、高范围）之一，将手臂保持在该位置三秒钟，回到起始位置，然后立即重复相同的关节屈曲角度，而将再现角度与原始角度之间的差异作为位置觉误差的度量。使用Vicon运动捕捉系统测量误差。受试者总共再现九个位置（每个范围3次试验，共3个范围）。
绝对重新定位误差（误差大小）的计算显示男性和女性之间无显著差异（p值≥0.05）。然而，误差方向（恒定误差）的分析显示性别之间存在显著差异，因为女性往往大多高估目标，而男性则既有高估也有低估目标的情况（p值≤0.01，观察效能=0.79）。结果还显示，与女性相比，男性的误差变化明显更大，表明其位置觉的变异性更大（p值≤0.05，观察效能=0.78）。
在恒定的关节位置觉误差中观察到的差异表明，男性和女性在上肢可能使用不同的神经肌肉控制策略。此外，在男性中观察到的较高的关节位置觉变异性可能是与女性相比其肌肉骨骼疾病发生率较低的因素之一。
本研究结果表明，作为神经肌肉控制系统一部分的肩部位置觉在男性和女性之间存在差异。这一发现有助于我们更好地理解女性，尤其是在工作环境中肌肉骨骼疾病发生率较高背后的原因。
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