Isotonic Vs. Isometric Contraction

Every exercise you do involves some sort of muscle contraction. Exercises with movement involve isotonic muscle contractions and exercises without movement involve isometric muscular contractions. Knowing the difference between these two different types of contractions can help you refine your workout routine, make the most of each exercise and get a comprehensive workout.

An isotonic contraction is any contraction is which a muscle shortens to overcome resistance. When a muscle shortens, at least one joint moves, and body movement occurs. The resistance can come from lifting a weight, pulling up your body, or from some other object such as when you lift a bag of groceries. An isotonic contraction involves two phases. The concentric phase occurs when muscle is shortened in an upward movement. The eccentric phase occurs when the muscle is lengthened in a downward movement.

Most gym exercises are isotonic exercises. Simple exercises such as pushups, squats, lunges and situps are all isotonic. Any weight machine that involves movement is also isotonic, such as lat pulldowns, chest presses and leg extensions. If you choose a weight on a machine that is too heavy for you to lift, and you push the handles but the machine does not move, your muscles are not contracting isotonically but rather isometrically, since no movement is occurring.

Isometric muscle contractions do not involve any movement. An isometric contraction occurs when your muscles push against a fixed resistance and no joint or body movement occurs. Even though there is no movement, your muscles are still working and contracting. If you are going to include isometric contractions in your workout, don't push too hard. Isometric contractions can significantly increase blood pressure, so don't hold your breath when doing these exercises and give yourself plenty of breaks. Talk to your doctor if you feel lightheaded or experience any chest pain during an exercise.

You can do isometric exercises in two different ways: By trying to move something that is too heavy for you to move or by holding static exercise poses. The second method includes plank holds, squat holds, side planks, abdominal holds, lunge holds and any other motionless exercise. Rather than counting repetitions, isometric exercises involve holding the position for a given amount of time, such as 30 seconds.