Abstract Motor performance patterns for mechanical assistance on unilateral force control can be affected by simultaneous muscle contraction. This study investigated how muscle activity and motor performance during the cooperation between dominant-arm force control and assistive force are affected by simultaneous non-dominant arm muscle contraction with inertial loading. Eleven participants (age: 24.1 ± 1.7 years) performed trajectory-tracking task based on visual feedback of real-time isometric force control. Their force for dominant-arm elbow flexion was released from reference magnitude of 47 N to magnitude of 23.5 N by providing mechanical assistance of a linear actuator. A 47 N of inertial loading on non-dominant arm elbow flexion was conditionally provided. For four time epochs of the experimental task, we measured responses of the assisted arm in terms of: (1) surface electromyography (EMG) amplitudes of biceps brachii and triceps brachii muscles, (2) peak perturbation, and (3) motor performance of force variability and target overshoot during manual force output. Simultaneous loading on unassisted arm did not affect peak perturbation of assisted arm. However, it caused lower force variability and overshoot ratio during the time epoch of force release and higher EMG amplitudes of biceps brachii muscle during the time epochs after mechanical assistance is provided, compared to the non-loaded condition. Our results indicate that simultaneous muscle contraction affects unilateral force control with mechanical assistance aimed at enhancing motor performance by creating extra agonist muscle activity. These findings can be utilized for improving the performance of human-robot cooperation during manual material handling in many industrial sites.

中文翻译：

---

单侧机械辅助和双侧肌肉收缩之间的运动表现模式

摘要 单侧力量控制机械辅助的运动表现模式会受到同时肌肉收缩的影响。这项研究调查了在优势臂力控制和辅助力之间的合作过程中，肌肉活动和运动表现如何受到同时具有惯性载荷的非优势臂肌肉收缩的影响。11 名参与者（年龄：24.1 ± 1.7 岁）根据实时等距力控制的视觉反馈执行轨迹跟踪任务。通过提供线性致动器的机械辅助，他们用于优势臂肘部屈曲的力从 47 N 的参考幅度释放到 23.5 N 的幅度。有条件地提供了对非惯用手肘屈曲的 47 N 惯性载荷。对于实验任务的四个时间纪元，我们在以下方面测量了辅助手臂的反应：（1）肱二头肌和肱三头肌的表面肌电图（EMG）幅度，（2）峰值扰动，以及（3）在手动力输出期间力变化和目标超调的运动性能. 在无辅助臂上同时加载不影响辅助臂的峰值扰动。然而，与无负荷状态相比，在提供机械辅助后的时间段内，它导致力释放时间段内的力变异性和超调率较低，而肱二头肌的 EMG 幅度较高。我们的结果表明，同时肌肉收缩会影响单侧力量控制，机械辅助旨在通过产生额外的主动肌活动来提高运动表现。