Any exercise which produces tension in the muscle without changing the length of the muscle is termed as isometric exercise. Now if you are in sitting position and you are flexing and extending your knees you are majorly working your quadriceps and hamstring muscles this is a form of active exercise where tension/contraction in a muscle is produced by changing the length of the muscle through active joint motion...... similarly now consider the scenario where you're lying down and pressing your heels and then your knees below the surface and holding it for 5 to 10 seconds now in this you are again producing tension in the muscle but without any movement of the joint or change the length of the muscle this is a static form of contraction/isometric exercise. benefits of isometric exercises are......... safe and easy to initiate. first line of treatment in rehabilitation. helps in strengthning an energizing muscle and to extent helps in stretching the muscle. makes the muscle fit and healthy. Brings the muscle to a stage from where active exercise and weight bearing Can be initiated. hope that answers your query. regards and take care.

3 types of exercises for improving muscle strength and endurance ●Isometric Exercises ●Isotonic Exercises ●Isokinetic Exercises In isometric exercises we do muscle contraction without movement of joint so that the muscle length remains same. In isometric exercises we hold the muscle in a contracted stage for 10 to 15 seconds so that by this manner we increase the strength of that muscle by holding it in a contracted manner. Initially we start with isometric and then shift to isotonic or isokinetic according to the case.