Abstract Awkward and extreme kneeling during roofing generates high muscular tension which can lead to knee musculoskeletal disorders (MSDs) among roofers. However, the combined impact of roof slope and kneeling posture on the activation of the knee postural muscles and their association to potential knee MSD risks among roofers have not been studied. The current study evaluated the effects of kneeling posture and roof slope on the activation of major knee postural muscles during shingle installation via a laboratory assessment. Maximum normalized electromyography (EMG) data were collected from knee flexor and extensor muscles of seven subjects, who mimicked the shingle installation process on a slope-configurable wooden platform. The results revealed a significant increase in knee muscle activation during simulated shingle installation on sloped rooftops. Given the fact that increased muscle activation of knee postural muscles has been associated with knee MSDs, roof slope and awkward kneeling posture can be considered as potential knee MSD risk factors. Practitioner Summary: This study demonstrated significant effects of roof slope and kneeling posture on the peak activation of knee postural muscles. The findings of this study suggested that residential roofers could be exposed to a greater risk of developing knee MSDs with the increase of roof slope during shingle installation due to increased muscle loading. Abbreviations: MSDs: musculoskeletal disorders; EMG: electromyography; ANOVA: analysis of variance; MNMA: maximum normalized muscle activation; RF: rectus femoris; VL: vastus lateralis; VM: vastus medialis; BF: biceps femoris; S: semitendinosus

中文翻译：

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瓦片安装过程中工作姿势和屋顶坡度对下肢肌肉激活的影响

摘要 盖屋顶时尴尬和极端的跪姿会产生高肌肉张力，这可能导致屋顶工人的膝盖肌肉骨骼疾病 (MSD)。然而，屋顶坡度和跪姿对膝部姿势肌肉激活的综合影响及其与屋顶工人潜在膝部 MSD 风险的关联尚未得到研究。目前的研究通过实验室评估评估了跪姿和屋顶坡度对木瓦安装过程中主要膝部姿势肌肉激活的影响。最大归一化肌电图 (EMG) 数据是从七名受试者的膝屈肌和伸肌中收集的，他们在斜坡可配置的木制平台上模拟木瓦安装过程。结果显示，在倾斜屋顶上模拟木瓦安装期间，膝部肌肉激活显着增加。鉴于膝部姿势肌肉的肌肉激活增加与膝部 MSD 相关，屋顶坡度和尴尬的跪姿可被视为潜在的膝部 MSD 风险因素。从业者总结：这项研究表明屋顶坡度和跪姿对膝部姿势肌肉的峰值激活有显着影响。这项研究的结果表明，由于肌肉负荷增加，在屋顶坡度增加的情况下，住宅屋顶工可能会面临更大的患膝 MSD 的风险。缩写：MSD：肌肉骨骼疾病；EMG：肌电图；ANOVA：方差分析；MNMA：最大标准化肌肉激活；RF：股直肌；VL：股外侧肌；VM：股内侧肌；BF：股二头肌；S：半腱肌