Vibration transmitted to the upper limb is the primary source of occupational musculoskeletal disorder. Transmissibility is not just caused by vibration magnitude but is also directly influenced by the applied force and posture. This study investigated the effects of two forearm postures and grip force levels, when using dual-handle guided equipment, on hand-arm transmitted vibration and physiological responses. Sixteen young male adults were recruited. Pre-task and post-task assessments including grip strength and perceived discomfort were measured. The task was to hold a vibrating handlebar for 5 -min under four randomly sequenced conditions: N/P_M/H—neutral/pronated forearm and mild/hard grip. Transmissibility and forearm muscle activities were recorded during each task. It was discovered that neutral posture led to higher wrist and elbow transmissibility, whereas hard grip resulted in higher elbow transmissibility, forearm muscle activities, grip strength reduction, and distal arm discomfort. Furthermore, the interaction between the effects of posture and force significantly influenced wrist extensor activity (N_H > P_H; N_M = P_M), proximal arm discomfort (N_H < P_H; N_M = P_M), and wrist transmissibility (P_H > P_M; N_H = N_M). Essentially, with constant vibration and exposure duration, the application of sustained hard grip had more negative physiological effects because of the greater physical workload toward the hands and forearms. Moreover, gripping hard during pronation led to higher discomfort that reached the proximal arm because a greater effort was required. Hence, a neutral forearm posture is recommended when the tasks require forceful movements and either posture is suggested when less powerful movements are involved.

中文翻译：

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两种握力水平和前臂姿势对手臂传递振动和生理反应的影响

传递到上肢的振动是职业性肌肉骨骼疾病的主要来源。传递性不仅由振动幅度引起，还直接受到施加的力和姿势的影响。本研究调查了使用双手柄引导设备时两种前臂姿势和握力水平对手臂传递振动和生理反应的影响。招募了 16 名年轻男性成年人。测量了任务前和任务后的评估，包括握力和感知的不适。任务是在四种随机排序的条件下保持振动车把 5 分钟：N/P _M/H- 中性/内旋前臂和轻度/硬握。在每项任务期间记录可传递性和前臂肌肉活动。研究发现，中立姿势导致较高的手腕和肘部传递性，而硬握导致较高的肘部传递性、前臂肌肉活动、握力降低和手臂远端不适。此外，姿势和力量之间的相互作用显着影响了腕伸肌活动（N _H  > P _H；N _M  = P _M）、近端手臂不适（N _H  < P _H；N _M  = P _M）和手腕传递率(P _H  > P _M ; N _H = _NM )。本质上，随着持续的振动和暴露时间，持续用力握力的应用会产生更多的负面生理影响，因为对手和前臂的身体负荷更大。此外，在旋前时用力抓握会导致到达近臂的不适感更高，因为需要更大的努力。因此，当任务需要用力的动作时，建议采用中立的前臂姿势，而在涉及较弱的动作时，建议使用任一姿势。