Subtle Kinematic Changes During One-Arm Pulling and Their Implications on Upper Extremity and Trunk Moments

OCCUPATIONAL APPLICATIONSSmall deviations in individual joint angles (<5°) simulated using a simple probabilistic computational model resulted in significant and meaningful changes in upper limb and trunk joint moments, by up to 20% of mean population joint strength. Moment tradeoffs between the upper extremity and trunk were also observed and depended upon work height and individual anthropometrics. Our work challenges the common practice of ergonomists and human factors practitioners to analyze task demands based on one representative posture. We recommend practitioners instead consider variability in adopted postures, as captured by monitoring worker kinematics over the course of a day. The sensitivity of joint demands to small postural changes also underscores the need for using reliable kinematic measurement tools in the field, since results from ergonomic analyses and consequently decision-making can be susceptible to large discrepancies despite small differences in postural inputs.