Exercises can be classified based on the engaged muscle's length and tension. Isotonic exercises involve an eccentric or lowering phase, and a concentric or lifting phase. Isometric exercises are those that do not produce joint movement but have tension developed within the muscle to support a load.
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Isotonic and isometric exercises can both be used to develop stability and muscle endurance, while isotonic exercises are generally better for increasing functional strength.
Read More: Isometric Exercises for Lower Back
Concentric Vs. Eccentric Exercise
Isotonic exercise can be further broken down into two categories: concentric and eccentric. Concentric exercise occurs when a contraction causes a muscle to shorten. For example, your biceps muscle shortens as your elbow bends during a dumbbell curl.
Eccentric exercise occurs when a muscle is contracting, but also getting longer. Lowering the dumbbell back to the starting position of a curl is one example of an eccentric exercise. These types of exercise, sometimes called negatives, are one of the biggest causes of delayed onset muscle soreness (DOMS), according to the American College of Sports Medicine.
Isolation Isotonic Exercise
An isolation isotonic exercise involves movement around a single joint. Isolation exercises are used by body builders to target specific areas of their body. Examples of isolation isotonic exercises include leg extensions, leg curls, seated and standing calf raises, side lateral shoulder raises, front shoulder raises, pec deck flies and preacher curls.
The primary muscle involved in producing the joint movement is called the agonist and is the target muscle in this type of exercise.
Compound Isotonic Movement
Compound isotonic movement occurs at more than one joint. As well as requiring an agonist, compound exercises also recruit muscles called synergists to assist in the movement.
Synergist muscles tend to be smaller than agonists. In overhead pressing exercises, the agonist is the triceps, while the synergist is the deltoid. Examples of compound isotonic exercises include push-ups, pull-ups, barbell presses, squats, lunges and dead lifts.
Compound exercises typically are more functional, as they mirror everyday or sporting movements and have a carry-over to real life activities, according to ExRx.net.
Lower Body Exercises
Your lower body contains the majority of your overall muscle mass. A strong, well-developed lower body can make everyday tasks such as walking, climbing stairs and standing easier. You can develop your lower body conditioning by performing isometric exercises.
One of the main isometric exercise benefits is that these activities do not require any equipment and thus are ideal for doing at home. Lower body isometric exercise examples include the wall squat hold, lying hip bridge, static lunge hold, static knee extension and knee squeezes against a pillow or small medicine ball.
Upper Body and Core Exercises
Although your upper body and core represent a smaller area of muscle than your lower body, these muscles are no less important. Strong upper body and core muscles help you lift heavy objects by supporting your spine, stabilizing your shoulders and encouraging good posture.
You can increase your strength in your upper body exercises by performing isotonic push-ups or pull-ups and self-resisted biceps curls. Isometric core exercises include planks, side planks, abdominal vacuums, wrestler's bridges and isometric crunches.