Northwestern Polytechnical University, Xian, P.R. China (Key Laboratory of Industrial Design and Ergonomics, Ministry of Industry and Information Technology)
Taiyuan University of Science and Technology, Taiyuan, P.R. China (Mechanical Engineering College)
Int J Occup Med Environ Health. 2019 Jul 15;32(4):537–552. doi: 10.13075/ijomeh.1896.01387.
The objective of this study was to assess the postures that were commonly used in automobile chassis repair operations, and to evaluate shoulder girdle muscle fatigue for different combinations of the weight of hand-tools.
Two right muscles, including upper trapezius (UT) and middle deltoid (MD), were selected. Surface electromyography (SEMG) and a perceived level of discomfort (PLD) were used to assess the degree of shoulder girdle fatigue. Fifteen healthy young male subjects from the Northwestern Polytechnical University participated in the test. The test consisted of assuming 4 different postures and maintaining each of them for 60 s. The 4 postures varied in terms of dumbbell weights, standing for the hand-tools weight: W1 was 0.48 kg and W2 was 0.75 kg; the 4 shoulder postures were shoulder flexions of 150°, 120°, 90°, and 60°, combined with an included elbow angle of 180°, 150°, 120° and 90°, respectively. The experimental sequences were randomly selected. The signals of SEMG and the values of PLD in the shoulder girdle were recorded in 60 s. All subjects completed the whole test. The repeated measure analysis of variance (ANOVA) was performed to ascertain differences between dumbbell weight (0.48 kg and 0.75 kg) and shoulder postures (150°/180°, 120°/150°, 90°/120° and 60°/90°). The Friedman test was utilized to determine the significant differences for UT(PLD) and MD(PLD) on shoulder postures. Spearman’s correlation was used to analyze the relationship between the subjective and objective measurements.
Significant correlational relationships existed between the UT percentage of the maximal voluntary electrical activation (%MVE) and UT(PLD) (r = 0.459, p < 0.01), between MD(%MVE) and MD(PLD) (r = 0.821, p < 0.01). The results showed that SEMG and PLD of the 4 postures under analysis differed significantly (p < 0.05).
It was indicated that posture T4 (shoulder forward flexion 60° and included elbow angle 90°) resulted in the lowest fatigue, both in terms of the objective measure and the subjective perception, which meant that this posture was more ergonomic. Int J Occup Med Environ Health. 2019;32(4):537–52
本研究旨在评估汽车底盘维修操作中常用的姿势，并评估不同手持工具重量组合下肩部肌肉的疲劳程度。
选择两块右侧肌肉，包括上斜方肌（UT）和中三角肌（MD）。使用表面肌电图（SEMG）和感知不适程度（PLD）来评估肩部疲劳程度。来自西北工业大学的 15 名健康年轻男性参与了测试。测试包括假设 4 种不同姿势，并每种姿势保持 60 秒。4 种姿势在哑铃重量方面有所不同，分别代表手持工具的重量：W1 为 0.48kg，W2 为 0.75kg；4 种肩部姿势分别为肩部前屈 150°、120°、90°，肘部夹角分别为 180°、150°、120°和 90°。实验顺序随机选择。在 60 秒内记录肩部肌电图信号和 PLD 值。所有受试者均完成了整个测试。采用重复测量方差分析（ANOVA）确定哑铃重量（0.48kg 和 0.75kg）和肩部姿势（150°/180°、120°/150°、90°/120°和 60°/90°）之间的差异。采用 Friedman 检验确定 UT（PLD）和 MD（PLD）在肩部姿势上的显著差异。采用 Spearman 相关分析来分析主观和客观测量之间的关系。
UT 的最大随意电激活百分比（%MVE）与 UT（PLD）之间存在显著的相关性（r = 0.459，p < 0.01），MD（%MVE）与 MD（PLD）之间存在显著的相关性（r = 0.821，p < 0.01）。结果表明，分析的 4 种姿势的 SEMG 和 PLD 差异有统计学意义（p < 0.05）。
结果表明，姿势 T4（肩部前屈 60°，肘部夹角 90°）在客观和主观感知方面疲劳程度最低，这意味着该姿势更符合人体工程学。国际职业医学与环境卫生杂志。2019；32（4）：537–52
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