According to various studies, one of the most effective ways of muscle strengthening is by using the method of isokinetic exercise.
This type of exercise is performed at a fixed range of motion, with stable angular speed of execution.

isokinetic exercise there is no interest in the amount of resistance that is applied against the action of the muscles.
The important part here is the speed of motion. 
This speed actually determines the resistance of the dynamometer according to the intensity   of effort.

Humac/Cybex is an isokinetic machine that is used to exercise, measure and evaluate the muscular system of  the body and therefore, helps guide the patients correctly to the appropriate fitness/rehabilitation programs.