[Potential elastic energy and muscular work (author's transl]

The relationship between the integrated EMG of the biceps (Qs) and positive work (W) was examined for isolated and to and fro movements of the elbow. The movements were performed against either pure inertias or against load. 1. In all cases, a linear QB--W relationship was found. 2. For isolated movements, the QB--W curve showed the same slope whether the movement was carried out against an inertia or against a load. 3. When the movements were carried out against an inertia, the slope of the QB--W curve was steeper for isolated movements than for to and fro ones. These results show that: a) for the movements against a load, the extra component of the integrated EMG arising from the initial isometric phase is compensated by the mechanical work resulting from the release of potential elastic energy; b) for the to and fro movements, elastic energy is stored in the stretched series elastic component during the negative work and released during the positive work. However, in this case, the biceps cannot escape from performing negative work which is necessary to decelerate the extension movement and so, it appears less energy expenditure relatively to the isolated movement.