Isokinetic is a term used to describe a type of movement.
The word isokinetic is most commonly used in sports science and medicine.
In these settings isokinetic defines a type of exercise (or a strength test).
Translated literally isokinetic (i·so·ki·net·ic pronounced ī'sō-kə-nĕt'ĭk) means movement at a constant speed.
In real life isokinetic means moving a resistance at a constant speed.
The key to isokinetic exercise is:
The speed of the motion remains the same even if the resistance alters (this is contrary to Dorlands medical dictionary who have the definition wrong!).
Probably the easiest way to think of isokinetic movement is to first consider the most common type of movement we human beings perform:
In almost every situation, every day, we perform isotonic movements. In these types of movements we pick up a fixed weight, let's say a dumbbell or even an empty pan. The weight of the dumbbell/pan is fixed but we decide how fast to lift it. We can lift it slow, fast, or anywhere in between. The key to this type of movement is we decide how fast it goes but the weight (resistance) remains constant.
In isokinetic movements the situation is reversed now we tell an isokinetic machine to move only at a certain speed (normally described in degrees per second). The machine will then vary it's resistance against us to maintain that speed. This means if we push against the machine hard it will give back allot of resistance to maintain the speed it was told to go at.
To achieve isokinetic movement there are many different ways of developing the resistance, however, most people use an isokinetic device. Isokinetic devices are referred to as isokinetic machines and they vary vastly in technology and price.
Most medical isokinetic machines are top of the range. They use a powerful motor to provide the isokinetic resistance to the force applied and then use a computer to keep the motion smooth, provide the acceleration and to record the results. In medical systems the components (the motor, gear box and computer control) are what make the machines so very expensive but they are also the parts that make them so very good.
Other isokinetic machines use cheaper ways of developing the isokinetic motion. These methods include (but are not exclusively) hydraulic systems (water or oil commonly) clutch based systems (not really used anymore due to noise and running costs), friction based systems and elastic resistance machines.