Fatigue-induced increase in movement variability does not come at a cost of worse performance in a repetitive pointing task

• Neuromuscular strategies employed in multijoint movements during repetitive motion-induced fatigue are still unclear, and movement variability may present a novel way to understand the compensatory control mechanisms that occur during fatigue. The aim of this study was to assess changes in shoulder and elbow joint kinematic variabilities and shoulder-elbow coordination variability associated with neck-shoulder fatigue, and whether these changes affected the spatio-temporal aspects of task performance. Nineteen healthy young adults continuously performed a repetitive pointing task between two targets placed in front of them at shoulder height at 1 Hz until fatigue (Borg CR10 rating of 8). Shoulder and elbow kinematics were recorded and used to compute shoulder abduction-adduction and elbow flexion-extension joint angles, and fingertip trajectories were used to compute the movement time and 3D spatial coordinates of the endpoint in each repetitive pointing movement cycle. Cycle-to-cycle movement variability of the shoulder and elbow joint angles from 15 consecutive forward pointing movements and cycle-to-cycle variability of continuous relative phase between the shoulder and elbow joint angles were compared between the first (baseline) and last (fatigue-terminal) minutes of performance. Shoulder kinematic variability and shoulder-elbow coordination variability were found to significantly increase with fatigue (by 60% and 30% of their respective baseline values). However, movement timing errors and spatial variability of the endpoint were found to be unchanged with fatigue. Results suggest that fatigue-related increase in shoulder variability may have been compensated by changes in shoulder-elbow coordination with an overall task performance objective and associated hierarchical control mechanisms.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Arbetsmedicin och miljömedicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Occupational Health and Environmental Health (hsv//eng)

Nyckelord

multijoint movements

arm kinematics

fatigue

coordination variability

relative phase

performance metrics

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)