Relationship between work constraints and the development of musculoskeletal disorders of the wrist: A prospective study

A 2-year prospective study was conducted on 184 workers about the relationship between the development of musculoskeletal wrist disorders (WD) and the occupational constraint parameters at their job (wrist angles, forces, repetitiveness and angular velocities), taking into account personal and occupational confounding factors. The results demonstrate a greater probability of developing WD for the workers suffering from chronic diseases, from psychological disorders, practising a sport involving the upper limbs and judging their work tiring. All occupational constraint factors are correlated except for the angles. Logistic correlation analyses show that the most significant associations with a greater probability of developing WD are observed for the mean relative EMG value recorded on the finger and hand flexors and the time during which the velocity in flexion–extension is greater than 50°/s. None of the angular parameters shows any association. Relevance to industry The study shows that the main factor on which to act in order to reduce the risk of WD is clearly the forces exerted by the hand. The objective of the control measures should be to reduce the muscular activity of the finger and hand flexors below 15% of the maximum activity corresponding to the maximum voluntary contraction of the finger flexors. A reduction of these forces appears to be associated with a reduction of the angular velocities of the wrist and of the repetitiveness.