Caractéristiques physiques d'un circuit résistant en poulie-thérapie

In a weight-and-pulley circuit, torque is the product of the lever arm by the force (R) applied to the fastening point of the rope. Rocher [7] defined this force R as the sum of the load and the frictional forces (100 g per pulley). By this fact, he omitted the forces linked to inertia and elastic properties of the circuit. We measured R during an ab-adduction movement at the hip in order to evaluate quantitatively the relevance of these two phenomenons. R varies greatly during a movement (from 0 to 300% of the weight attached to the rope). The dynamic frictional forces depend on the number of pulleys but increase also with the load. By changing the components of the circuit (rope and cage), one can reduce the frictional forces and the oscillations resulting from the lack of rigidity. However, the forces linked to inertia are inherent to a weight-and-pulley circuit since the 'resistance' opposed on the movement is linked to a mass. Possible therapeutic inferences are discussed