Shoulder motion assistance using a single-joint Hybrid Assistive Limb robot: Evaluation of its safety and validity in healthy adults.

PURPOSES

To evaluate the feasibility of using the single-joint Hybrid Assistive Limb robot (HAL) to assist with shoulder flexion-extension in healthy adults, and to assess the capacity of the HAL to analyze the bioelectrical signals of muscle activity for shoulder flexion-extension.

METHODS

This cross-sectional feasibility study included six healthy adult men with no impairment in shoulder motion. The single-joint HAL was fixed to a custom-designed platform and upper arm attachment, and aligned 3 cm below the acromion process. Vital signs, shoulder fatigue, and shoulder pain were evaluated before and after the shoulder elevation exercise performed with and without the HAL. Activity of selected muscles of the shoulder was recorded using a wireless superficial electromyography device. Shoulder movement was captured using a three-dimensional motion analysis system.

RESULTS

The HAL supported smooth flexion-extension of the arm at the shoulder joint, with no negative effects on vital signs, shoulder fatigue, and shoulder pain. The HAL decreased muscle activity levels, with a 55% decrease in trapezius muscle activity. The upward rotation angle of the scapula was significantly lower with the HAL at 120° of shoulder flexion.

CONCLUSION

The single-joint HAL provided safe and effective assistance to scapular plane shoulder flexion-extension among healthy adults.