Definition of Isotonic Exercises

Mid section of a woman lifting dumbbell weight in gym

Isotonic exercises provide a powerful workout for beginners and professional athletes alike. Most people perform isotonic exercise without realizing the technical term for the movement. In short, an isotonic exercise forces muscles to carry a static weight throughout a range of motion. So basically, any form of weight training, with either free weights or machines, qualifies as isotonic. The common biceps curl, in which you lift a dumbbell to work the upper arm, is a classic isotonic exercise.


All isotonic exercise features resistance. Forcing the muscles to strain against this resistance builds strength and power. Isotonic exercise doesn’t require expensive equipment. If you can’t afford dumbbells and free weights, any static weight, from bricks to sacks of sand could be used to offer the necessary resistance. If all else fails, you can even use your own body weight as resistance, as in pushups and pullups.


There are two main types of isotonic exercise: concentric and eccentric. In concentric isotonic exercise, the muscle shortens in response to the greatest resistance, as when performing a biceps curl. In eccentric isotonic exercise, the muscle experiences the same level of resistance throughout the entire motion, forcing the muscle to lengthen. Pilates would be an example of eccentric isotonic exercise.


Along with building strength, isotonic exercises also offer the ability to specifically customize a workout for a specific athletic goal. For instance, hockey players looking to improve their skating can perform isotonic exercises for the legs to build lower body strength. Baseball players intent on adding more power to their swing can work their arms and shoulders with isotonic exercises.


Performing isotonic exercises with light weights at higher repetitions will build lean, strong muscles over the entire range of motion. However, if you’re looking to add muscle mass and power, opt for fewer reps at much higher weights. You tax your muscles beyond their comfort level by lifting heavier weights, causing tiny tears within the muscle fibers. When these tears heal, they actually enlarge the muscle, resulting in more muscle mass.


Despite similar sounding names, isotonic exercise differs greatly from isometric exercise. Isotonic exercise requires movement, activating the muscles and joints to lift a static weight. In isometric exercise, the muscles flex and strain without movement of any kind. An example of an isometric exercise would be pushing your two hands together to strengthen your arms and chest; the muscles fire even though the targeted body parts never move.