Occupational Safety and Health Laboratory

Carpenters frequently work in awkward and stooped postures. Autofeed extension screw guns (ESGs) allow certain tasks to be performed upright. This study evaluated low back and wrist motion in fifteen carpenters using a traditional screw gun (TSG) and ESG during floor level work. ESG use required a greater percentage of time in awkward wrist postures with higher velocities and accelerations, yet neither tool placed workers at risk for wrist injury. The ESG resulted in significantly less low back flexion, left-sided bending and twisting, velocity and acceleration. The probability of low back disorder group membership risk was 53% with TSG use and 47% with ESG use. Carpenters liked using ESGs and reported less exertion when using them. The ESG's autofeed feature enhanced productivity. Training may be important to further reduce back flexion and improve tool maintenance, and design changes would improve ESGs overall.