The influence of precision requirements and cognitive challenges on upper extremity joint reaction forces, moments and muscle force estimates during prolonged repetitive lifting

• Published in: Ergonomics 2014-02, Vol.57 (2), p.236-246
• Main Authors: Joseph, Caroline, Beach, Tyson A.C., Callaghan, Jack P., Dickerson, Clark R.
• Format: Article
• Language: English
• Subjects: Adult; Attention; Biological and medical sciences; Biomechanical Phenomena - physiology; Biomechanics; Cognition; cumulative loading; Elbow Joint - physiology; Ergonomics; Ergonomics. Human factors; Fundamental and applied biological sciences. Psychology; Humans; Lifting; Male; manual handling; mental processing; Muscle Contraction; Muscle, Skeletal - physiology; Muscular system; musculoskeletal disorders; Occupational Health; Occupational psychology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Shoulder; Shoulder Joint - physiology; Task Performance and Analysis; Wrist Joint - physiology; Young Adult
• ISSN: 0014-0139; 1366-5847
• DOI: 10.1080/00140139.2013.869359

Prolonged repetitive lifting is a whole-body exertion. Despite this, the roles and physical exposures of the upper extremities are frequently neglected. The influence of precision requirements and cognitive distractions on upper extremity responses when lifting was evaluated by quantifying several biomechanical upper extremity quantities. Nine participants completed four 30-min lifting tasks with and without simultaneous cognitive distractions and/or precision placement constraints. Specific metrics evaluated were joint reaction forces and moments (wrist, elbow and shoulder) and modelled shoulder muscle forces (38 defined shoulder muscle mechanical elements). The addition of a precision requirement increased several metrics by up to 43%, while the addition of the cognitive distraction task had minimal influence. Furthermore, several metrics decreased by up to 14% after the first 10 min of lifting, suggesting a temporal change of lifting strategy. Practitioner Summary: Lifting tasks often include precision placements and cognitive demands. This study shows that precision placement during prolonged repetitive lifting increases upper extremity forces and moments, while the addition of a cognitive task is benign. Furthermore, field assessments of repetitive lifting should include observations longer than 10 min, as adaptive strategies appear to be adopted.