Master of Science in Industrial Engineering (MSIE)


Mechanical Engineering

Document Type



Finding a proper work/rest schedule is considered an important factor for improved efficiency, safety, and a higher rate of productivity in the workplace. The purpose of this study was to determine the optimum rest period for lifting tasks using heart rate, perceived exertion, and physical strength. First, the maximum acceptable weight of the box to be lifted was determined for each one of 10 participants using a psychophysical approach. Then on separate days, participants were required to repetitively lift the box from knuckle height to shoulder height for 20 minutes. They were then allowed to rest 5, 10, 15, or 20 minutes. After each rest period, the participants repeated the same lifting task. Before and after each lifting task, measurements for heart rate, perceived exertion (Borg scale), static arm strength, and hand strength were recorded. The relationship between four dependent variables (heart rate, Borg scale value, static arm strength, hand (grip) strength) and two independent variables of the experiment (resting time/phase effect), and the interactions effect was examined by the experimenter, through conducting a statistical analysis (Two-Way Repeated-Measures ANOVA) and pairwise comparison test (Post Hoc test). In addition the trend lines for all dependent variables were investigated as an additional analysis. The recovery percentages of heart rate, along with the statistically significant results of perceived exertion, indicate that 15 minutes of rest is the optimum rest period. The hand strength graph suggests that at least 10 minutes is needed for recovery. The trend for static arm strength did not show any particular correlation or pattern. The overall findings of this study suggest that workers should be provided with 15 minutes of rest to recover from a 20 minute repetitive lifting task.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Aghazadeh, Fereydoun