isokinetic

Isokinetic refers to muscle contractions that occur at a constant speed. In practice, isokinetic contractions are produced and controlled with a device such as an isokinetic dynamometer that imposes a fixed angular velocity at a joint while the subject contracts the muscle. The resistance varies to maintain that constant speed. Isokinetic contractions can be concentric (muscle shortening) or eccentric (muscle lengthening) and differ from isometric contractions (no change in length) and from isotonic contractions (load remains constant while speed varies).

Applications include isokinetic testing and rehabilitation. Dynamometers measure muscle performance during contractions at predefined velocities, yielding metrics such as peak torque, total work, and power for joints like the knee or elbow. These data help assess strength imbalances, track recovery after injury, and guide rehabilitation programs. They may also be used for training at specific speeds under controlled conditions.

Isokinetic exercise is a training modality that uses the same principle to maintain a constant movement speed while the user exerts maximal or submaximal effort. Accommodating resistance enables smooth movement through a full range of motion and allows training of both concentric and eccentric actions at chosen velocities. It is commonly used in rehabilitation, including after knee surgery, and can help improve strength at targeted speeds.

Limitations and considerations include limited transfer to many functional activities that occur at variable speeds, equipment cost and accessibility, and dependence on proper technique and motivation. Results are influenced by joint angle, velocity, and individual factors such as age and injury status. Safety considerations and contraindications should be observed.