Power output during knee extension/flexion movement performed in controlled mechanical conditions

In order to investigate how exercise, performed under controlled mechanical conditions, might be influenced by variables such as fatigue and immobilization, a computerized transducer system was specially built. Quadriceps femoris and knee flexors were studied in healthy non-athlete and post-meniscal surgery subjects, by means of an isokinetic extension-flexion protocol. The protocol was applied before and after cycloergometer "fatiguing" effort in the healthy subjects and before and after re-training in the surgical ones. An original software was able to display the time course of dynamic parameters, particularly force, velocity and power output. Results obtained showed a 26.5% significant decrease in power output after the effort, owing to a concomitant decrease in velocity, while force increased, but over a longer time. As to the operated subjects, power output was higher following retraining, as a result of the combination of lower force and higher velocity. The transducer system proved reliable in detecting changes in power output, whatever the cause. The instantaneous control of variables which power is depending upon, such as force and velocity, may give a few hints on the efficacy of training and rehabilitation programs.