The effects of force and exertion duration on duty cycle time: Implications for productivity

Abstract

Ergonomics has positive effects on both physical health and productivity, but estimating productivity benefits is difficult at the task design/redesign stage. Rest allowance prediction models are not suitable for repetitive short cycle dynamic tasks and MTM techniques are limited in their suitability for considering ergonomics risk factors such as posture and force. The purpose of this study was to investigate the relationship between force and exertion duration on self selected duty cycle time and discomfort. Twenty one participants completed repetitive upper limb exertion treatments, each of duration ten minutes. Five levels of Force (10, 20, 40, 65 and 80% MVC) and Exertion period (1, 2, 4, 6.5 and 8 seconds) were investigated. The psychophysical adjustment method was used whereby participants self selected a work pace for the second half of each treatment. Duty cycle, derived from the self pace cycle time, was the measure of productivity effects in the experiment. ANOVA revealed a significant effect on duty cycle time for force, exertion period and the interaction (each p<0.0001). Friedmans test indicated a significant effect of force (p<0.0001) and exertion period (p<0.0001) on discomfort. Spearman's correlation analysis showed a strong correlation between discomfort and duty cycle time (p<0.05). Multiple regression analysis was used to develop a predictive model for duty cycle time based on force and exertion period, and this was a good fit to the data (R 2 = 0.98, p<0.05). Profiles were generated presenting zones of acceptable self selected duty cycle times based on force and exertion duration.

Effects of grip type and wrist posture on forearm EMG activity, endurance time and movement accuracy

“…Finneran and O'Sullivan (2010b) included 20% and 40% grip MVCs in the study of the effects of force and duration of exertion on self-paced duty cycle time in a simulated task. They found a significant difference between these two levels on discomfort and duty cycle time.…”

Gamified Motor Training With Tangible Robots in Older Adults: A Feasibility Study and Comparison With the Young

“…A supporting argument for the fatigue hypothesis could be that, during the first chunk of day 2, the participants started at a higher performance level compared to the first chunk of day 1. They may thus have recruited more endurance resources early during the daily session and may have reached their physical exhaustion phase faster on day 2 (Finneran and O'Sullivan, 2010). It is shown that motor learning procedures lead to better results when the practice is done over several days or even weeks (Shea et al, 2000).…”

Self-selected duty cycle times for grip force, wrist flexion postures and three grip types

“…Previously published studies by the current authors involved psychophysical experiments investigating and modelling the relationship between physical risk factors (force, duration of exertion, posture and grip type) and operator performance, with discomfort as a mediator (Finneran andO'Sullivan 2010a and2010b). The current experiment expands on those studies by studying the effects of grip type in conjunction with grip force and wrist posture on duty cycle time (as a measure of on-job productivity or presenteeism) in a simulated task.…”

“…Initial cycle time was set at 5 seconds so that DCT would be 40%. Models developed by Finneran and O'Sullivan (2010b) and Abu-ali et al (1996) found that in high force conditions average maximum DCT was approximately 40%.…”

“…the active time within a work cycle) was calculated from Self-Paced Cycle Time and exertion period based on definitions and work by Moore and Wells (2005), Abu-Ali et al (1996) and Finneran andO'Sullivan (2010a and2010b). Discomfort was measured once per minute over the 25 minute testing combination using a 100 mm Visual Analogue Scale (VAS).…”