Factors affecting applied grip force and a system for classifying the forceful aspects of manual work

This dissertation describes three related studies. The first evaluated the influence of load, coefficient of friction (COF), work pace, and grip/pinch strength on the amount of grip and pinch force used to perform a simulated industrial task. Loads represented an average of 6% to 21% of grip or pinch strength (MVC). The most significant predictor of pinch and grip force was the load-strength interaction. This interaction, plus the main effects of load and strength, explained 19% to 33% of the variation in performance data. Load alone accounted for 9% to 25% of pinch and grip force; strength, from 2% to 7%. For midcycle pinch force, in addition to the load-strength interaction, the pace-strength interaction was significant. COF and gender were not significant. Because applied force is largely voluntary, some variation in performance may be due to behavioral characteristics of the individual such as attentiveness and anxiety level.; The second study investigated the effect of COF on peak and static pinch force at loads representing an average of 10% to 70% MVC. The main and interaction effects of load and COF for peak and static force were significant; the COF effect was statistically significant (p {dollar}<{dollar}.01) only at the high load. These results indicate that high-friction handles are most effective in reducing force exertions for heavy objects.; The results of the first two studies increase our understanding of factors affecting manual force, a risk factor for cumulative trauma disorders. The final study described a system for classifying the forceful elements of manual tasks. The structural basis of the taxonomy is the primary work objective of a force element. The first four objectives involve direct hand use: MOVE, HOLD, DEFORM, and APPLY TORQUE. The fifth objective, USE TOOL, includes nine tool actions: Secure threaded fastener, Secure non-threaded fastener, Cut, Strike, Grind/Polish, Stretch/Compress, Stir/Spread, Drill, and Move/Hold. Force attributes are specified. The taxonomy can be used for hazard analyses and, potentially, for the development of a standard data system for estimating the force requirements of manual tasks.