Isometrics is a form of exercise which is practiced by causing the contraction of a muscle or muscle group by exerting a force on them. This, unlike traditional weight-training exercises, does not changing the length of the muscle, instead allowing it to remain static or stationary. With typical dynamic exercises that involve the movement of muscle length, either concentrically or eccentrically, the muscle length changes. The effect of a static contraction begins with the muscle recruiting its core components. These components, in general terms called "fibers," are recruited into an activation mode. Studies show that with isometrics, up to 5% more activation occurs than with dynamic exercise. In fact, nearly all fibers are recruited with isometrics. The force generated is dependent on the length of the muscle contracting. Maximum force is achieved with maximum muscle length.

General beliefs are that more strength can be achieved with static isometric exercise than with dynamic exercise. Isometric training has shown strength increases possible from 14-40% in 10 weeks. While isometric gains are typically found at the joint angles, there can be a 20-50% transfer with an angled contraction of 20 degrees. Using tension at specific angles of muscle length can isolate muscle strengthening.

Since there is less energy expended with isometrics, it does not significantly interfere with other aspects of training due to less fatigue. Isometrics can be an ideal exercise regimen that has been shown to improve muscle strength and mass while being more easily accomplished in less time. Of course, it is likely best to combine the use of isometrics with traditional exercise for the best possible results.