You are in Our Content Affiliates . To be an isometric exercise, a muscle must contract and develop force without changing its length or affecting a change in any joint angle. This is in contrast to dynamic exercise, such as running and weight lifting, which involves movement and changes in joint angles.
Isometric exercise differs from dynamic exercise in terms of physiology and applicability.
Dynamic exercise demands a lot of energy but causes the heart to work only moderately harder as it increases the volume of blood pumped to the muscles. Isometric exercise, on the other hand, requires less energy but makes the heart work much harder in response to the increased blood pressure caused by static muscle contraction. It is this sudden and potentially excessive increase in blood pressure that makes isometric exercise risky, especially for people with cardiovascular weakness or disease. Isometric contractions that require gripping something are more likely to cause a big jump in blood pressure than exercises that involve simply pressing against an immovable object. Furthermore, if the exercise is accompanied by that forceful act of breath holding known as the Valsalva maneuver, the resulting increase of pressure in the chest blocks blood from returning to the heart and rapidly drives blood pressure to dangerously high levels.