An analysis of grip design for manual hammer stapling tool

Three hammer stapling tools with distinctly different handle designs were evaluated in terms of comfort, safety and hand-arm stress. Sixteen male participants used each tool on two simulated roofs with 4:12 and 6:12 pitches, and stapled roofing underlayment at a frequency of 1 staple per second for two minutes. Tools with smooth, rounded and compressible grips, received significantly better ratings (p<.05) in grip comfort and ease of use, than the tool with rectangular grip cross-section employing a hard and serrated grip surface. Tools with grip features that provided protection from unintentional finger pinching received higher safety rating (p<.05). The tool with a 10 degree bent handle reduced (p<.05) the wrist angle at tool strike. The bent handle tool reduced the wrist flexor muscle activity, but increased the wrist extensor muscle activity. The findings of this study suggest that the hammer stapling tool with smooth and rounded grip cross-section, with a bent handle, improves grip comfort, usability and tool safety, and reduces the risk of repetitive strain injury of the wrist joint.