Isotonic exercise is a form of exercise which involves controlled contraction and extension of muscles and mobilization of the joints around those muscles. For exercise to be isotonic, the tension involved must remain constant throughout the exercise, rather than fluctuating. One of the most classic forms of isotonic exercise is weight lifting. This type of exercise tends to be inexpensive to perform, and it can be used to develop strength in both the muscles and the joints.
People sometimes confuse isotonic and isometric exercise, because the two terms sound very similar. The key difference is the presence of movement. In isotonic workouts, the joints move through a range of positions controlled by the user, while in isometric exercise, the joints remain stationary. Pressing one's palms against a wall and leaning into them to elongate muscles is an isometric exercise, while doing a pushup is an isotonic exercise.
Classically, isotonic exercise is used to support an overall fitness plan. People lift weights, do pushups and pullups, and engage in other types of isotonic exercise to make themselves more fit for a particular sport. A swimmer, for example, might use this type of exercise to build up the arms to be a more effective and powerful swimmer. Regular isotonic exercise can also promote healthy joints which will perform well into old age.
Light isotonic exercises are sometimes utilized in physical therapy programs to gently develop muscle and joint strength. The gentle elongation and contraction of the muscles which occurs during the exercise can be used to pinpoint problem areas, such as a point when a muscle experiences a very high level of strain. The exercise can also build up muscles and joints after surgery or trauma, with the guidance of a physical therapist or personal trainer who has experience.
Every person's body is different, and ideally an isotonic exercise program should be developed for a specific person, rather than being used generically. Professional athletes often develop such programs with their coaches and sports physicians to reach an optimal level of performance. Personal trainers, fitness instructors, and physical therapists can offer suggestions and help formulate appropriate programs to ensure that people are using the most suitable and effective set of exercises. For people who are just embarking on an exercise plan, it is a good idea to consult a physician, and to work with a trainer for the first few sessions to learn how to exercise safely and effectively.