Date of Award


Degree Type


Degree Name




First Advisor

Cort, Joel




The purpose of the present study was to determine if a relationship between what individuals chose as an acceptable workload and muscle effort existed. Additionally, physical capability limits for direct current right-angle power tool operation were established. A psychophysical methodology was utilized to examine 40 non-skilled female participants while performing a right-angle power tool fastening task on a simulated joint. A combination of two between subject variables were examined: joint orientation (horizontal and vertical planes) and joint hardness (hard and soft joints). Participants were evenly distributed into one of the four joint orientation-hardness groups via a minimization technique that reduced between group mean characteristics (i.e. height, weight, age, grip strength). Within each of these four groups, a combination of three fastening strategies (Automatic Tightening Control, Quick Step, and Turbo Tight) and three fastening frequencies (1/min, 3/min, and 5/min) were performed by each participant. The chosen target torque, forces experienced in all three orthogonal axes, and surface electromyography were gathered throughout the data collection. Separate mixed-design repeated analyses of variance were used to assess each of the dependent measures, with Tukey’s post hoc test comparisons as relevant (p<0.05). Fastening strategy and frequency influenced the target torque and forces participants chose as an acceptable workload, which was also supported by the surface electromyography data. Participants chose significantly higher target torques with the Turbo Tight strategy, which was associated with lower peak force and force impulse in comparison to the other two strategies. Participants chose to accept lower target torques and forces as fastening frequency increased. Physical capability limits were calculated to accommodate 75% of the female working population, which will help reduce the risk of injury associated with right-angle power tool use in the automotive sector and elsewhere.