Relationships among static strength, dynamic strength, and psychophysically determined levels of acceptable force for a pushing task and foot pedal actuation task

Static strength or psychophysical tests are commonly used to define the capabilities of a working population, but these data are not easily translated to the peak forces that users apply to products or the operational forces associated with product ease of use. This study investigated the relationships among static strength, peak forces from rapid exertions, and psychophysically determined levels of acceptable forces for 39 subjects depressing a foot pedal and pushing against a vertical surface. Peak forces were greater than static strength and psychophysically determined acceptable forces were less than static strength. The ratio of peak to static strength was greater for the pushing task than for the foot pedal task, likely because of the types of motor units recruited and the inertial effects of each exertion. Engineers should be mindful when using published strength values to generate requirements for product design. The ratios among static strength, peak force, and psychophysical limits appear to vary based on task and could affect product safety, effectiveness, and ease of use. •Static strength, peak strength, and acceptable force were measured for two activities.•The strengths of correlation and ratios among forces are dependent on activity.•Engineers should be mindful when using published static strength values for design.