Isometrics deals with the concept that muscles will get stronger without actually moving them through a range of motion. This is accomplished by challenging the muscle or muscle group to use more force. If there is enough resistance against a muscle then it will strengthen simply by trying to move something rather than actually moving it. Muscles contract to produce force, and eventually build strength, in three ways. First, concentrically, as when you lift a dumbbell, second, as when you lower a dumbbell, and third, isometrically, as when you hold a dumbbell in a fixed position where the muscle contracts without actually moving. Strength building requires only that the muscle contract, not move. Isometrics allows this to occur.

The advantages of isometrics include convenience since you do not need to go to a gym to perform the exercise. Isometrics can be done while at work, at home or at rest. You can use your own muscles in opposition to each other, like pushing your palms together. There is not a need for weight equipment or special machinery. Contractions need only last for 10 seconds to produce a result. Holding your feet off the floor will contract your abdominal muscles, or holding a stomach crunch will strengthen stomach and back muscles.

Research has shown that with isometrics more contractions over a shorter period of time are feasible as opposed to traditional isotonic exercising. Isometrics is not ideal for all situations. Athletic training that requires range of motion strength may need a combination of static and isotonic exercises. Since the muscles are strengthened only in the position of the contraction, a better overall effect will result if the angle is varied through the isometric contraction.