From operational leeway to motor variability and diversity in MSDS prevention

Musculoskeletal disorders (MSDs) remain a topical issue for both ergonomists and prevention actors. French-language ergonomics based on the central concept of activity has developed and mobilized a conceptual set to characterize work situations that weaken the health of operators. In the context of this article, we critically address the concept of operational leeway whose theoretical and conceptual basis seems unclear. We argue that the concept of operational leeway is based on a cognitivist conception of motor control that makes it unfit to account for motor variability, that is, the intrinsic variability of movement. Based on a theoretical framework of nonlinear dynamical systems, we show through an international literature review that motor variability plays an important functional role both in the production of motor performance and in the preservation of MSDs. Returning to the ergonomic of activity, we show that they are based more on the concept of motor diversity. Motor variability and motor diversity are nevertheless concepts that can be articulated within the same conceptual framework. In this sense, we conclude that the concepts of motor variability and motor diversity are conceptually more established than the concept of operational leeway and are likely to guide interventions in a more operational way by being quantifiable or objectivable.