This form of exercise is in contrast to the other forms in that it permits maximum muscle contraction throughout the full range of joint movement. You will often seen it referred to as "accommodating resistance exercise" (a term first introduced by Hislop and Perrine, 1967). The resistance is now variable in proportion to the change in muscular capability at every point in the range of motion. The variation is controlled so that at all times it equals the product of the muscular strength.

There are two major types of machine available to offer isokinetic exercise.
Type 1 an active dynamometer (the most familiar to clinicians) In this type of exercise the speed is controlled whilst resistance is variable according to the amount of force throughout the range of movement. No matter how much force the individual applies the speed does not change. Thus the motion of the body segment is kept at a predetermined velocity.

Type 2 utilizes a change in the moment arm of the selected resistance to coincide with the change in moment arm of the muscle effort and the change in tension due to muscle length change. The resistance thus accommodates the continuous changes in muscle force which occur throughout the range of movement.

The changes in the resistance arm on the machine are determined and pre-set to coincide with the average strength curves for various joint actions (obviously this involves a different machine for each movement).

Isokinetic exercise and testing have been available since 1970. The concept was far from an immediate a success. Isokinetics machines were few and far between with little or no feedback. The results we all love to hate were not available with exercise as the only option.

Isokinetic testing was originally a tool used mainly in exercise science and the only isokinetic movements available were concentric (with no thought given to isotonics, isometrics, continuous passive motion (CPM) or range of motion expansion).

Eventually, isokinetics found its way into therapy albeit with very rigid machines usually specific to a joint or small numbers of joints.

In the early 80’s (around 1984) the world of isokinetics changed dramatically. Servo motors and microprocessors transformed the early machines into fast and dynamic tools offering instant data analysis and reproducibility. This now meant that real time data became available and testing became as important as exercise.

The new machines now incorporated what we call today active dynamometry. It was at this stage that eccentric isokinetic testing and exercise became available. This change in the fundamental data collection process finally sparked large scale interest in isokinetic testing.

Tag: Isokinetic exercise