Influence of disruptive design changes of a hammer drill on user posture and muscle stress : An exploratory study

Repetitive physically demanding tasks, such as operating power tools, can cause work-related musculoskeletal disorders, particularly in the shoulder-arm region. Despite the need for ergonomic product designs, it is often unclear how to adjust power tool design to reduce user stress. This study explores how handle positions and orientations of a hammer drill impact joint angles and muscle activation. An adaptive hammer drill was developed, and three participants performed horizontal drilling tasks. Measurements using motion capture, electromyography, and force sensors revealed that handle configurations affect user posture and muscle activation. Key findings indicate increased handle tilt and angle result in asymmetrical postures and higher muscle activation. In contrast, closer handle positioning promotes balanced force distribution of the left and right sides. Future studies will further investigate these findings with a larger number of subjects and a reduction of noisy factors such as vibration.