Joint moment trade-offs across the upper extremity and trunk during repetitive work

• Published in: Applied ergonomics 2020-10, Vol.88, p.103142-103142, Article 103142
• Main Authors: Mulla, Daanish M., McDonald, Alison C., Keir, Peter J.
• Format: Article
• Language: English
• Subjects: Adult; Biomechanical Phenomena; Cumulative Trauma Disorders - etiology; Cumulative Trauma Disorders - physiopathology; Elbow Joint - physiology; Ergonomics; Fatigue; Humans; Male; Muscle Fatigue - physiology; Occupational Injuries - etiology; Occupational Injuries - physiopathology; Shoulder; Shoulder Joint - physiology; Task Performance and Analysis; Torso - physiology; Upper Extremity - physiology; Variability; Weight-Bearing - physiology; Young Adult
• ISSN: 0003-6870; 1872-9126
• DOI: 10.1016/j.apergo.2020.103142

Individuals can coordinate small kinematic changes at several degrees of freedom simultaneously in the presence of fatigue, leaving it unclear how overall biomechanical demands at each joint are altered. The purpose of this study was to evaluate trade-offs in joint moments between the trunk, shoulder, and elbow during repetitive upper extremity work. Participants performed four simulated workplace tasks cyclically until meeting fatigue termination criteria. Emergent fatigue-induced adaptations to repetitive work resulted in task-dependent trade-offs in joint moments. In general, reduced shoulder moments were compensated for by increased elbow and trunk joint moment contributions. Although mean joint moment changes were modest (range: 1–3 Nm) across participants, a wide distribution of responses was observed, with standard deviations exceeding 10 Nm. Re-distributing biomechanical demands across joints may alleviate constant tissue loads and facilitate continued task performance with fatigue but may be at the expense of increasing demands at adjacent joints. •Fatigue-inducing repetitive work promoted joint moment trade-offs redistributing loads across the trunk and upper extremity.•Generally, reduced shoulder joint moments were compensated for by increasing trunk and elbow joint moments.•Kinetic adaptations with repetitive work were highly variable between participants.