The biomechanical characteristics and physiological cost of three standardized pulling tasks

Purpose: The purpose of this study was to investigate the biomechanical characteristics and physiological cost of three standardized pulling tasks. 12 female and 17 male subjects participated in the study. The subjects were instructed to pull a load at three different heights (hip, shoulder, eye – anatomical landmarks defined the end of a pull) at a rate of ten pulls per minute, for a period of ten minutes (one hundred total pulls). The pulls were sub-maximal and chosen to represent a task during a typical 8 hour workday.

Statistics: ANOVA statistical analyses with Bonferroni pairwise comparisons were performed to determine significance.

Results: Statistical significance was obtained for energy expenditure (Ė), sagittal displacement and twisting velocity. Hip pulling Ė was lower than shoulder pulling Ė (p=0.046) and eye pulling Ė (p=0.002) by 7% and 11%, respectively. Hip pulling involves less sagittal displacement than shoulder (p=0.004) and eye (p=0.001) by 37% and 46%, respectively. Finally, twisting velocity at hip (p=0.042) and shoulder (p=0.006) pulling were 30% and 36% higher than twisting velocity at eye pulling.

Conclusion: Physiological data combined with biomechanical data provide a comprehensive description of the demands associated with this standardized pulling task. This combined information assists in risk factor identification and intervention design for tasks involving repetitive upper limb movements.