Adaptations to fatigue during a repetitive multiplanar lifting task.

Warehouse workers are often required to perform physically demanding repetitive lifting tasks leading to fatigue. Previous research has primarily focused on constrained lifting tasks when investigating fatigue. The purpose of the current study was to investigate fatigue-based movement adaptations during a multiplanar, ecologically relevant lifting task. Participants (n = 28) lifted, transferred, and lowered a mass continuously for 60 min. Full body kinematics and muscle activity of the lumbar erector spinae, rectus abdominis, external oblique, and anterior deltoids were collected continuously. Results suggest that the load moment arm decreased across the trial (4% decrease), and participants tended to complete movements faster (4% decrease). Further, participants exhibited less variability in thorax-pelvis flexion deviation phase when fatigued (9% decrease). Finally, rectus abdominis activity increased (4%MVIC increase), while anterior deltoid activity decreased over time (2% decrease). These behavioural, coordination-based, and muscular adaptations to fatigue all have potential implications for injury risk in repetitive lifting tasks.