Isotonic and isometric exercises

Good muscle tone improves coordination. When muscles are slightly contracted, they can react more rapidly if and when greater exertion is necessary. Muscles with poor tone are usually soft and flabby, but exercise will improve muscle tone.

There are two general types of exercise: isotonic and ismetric. In isotonic exercise, muscles contract and bring about movement. Jogging, swimming, and weight lifting are examples. Isotonic exercise improves muscle tone, muscle strength, and if done repetitively against great resistance (as in weight lifting), muscle size. This type of exercise also improves cardiovascualr and respiratory efficience, because movement exerts demands on the heart and respiratory muscles. If done for 30 minutes or longer, such exercise may be called "aerobic," because it strengthens the geart and respiratory muscles as well as the skeletal muscles.

Isometric exercise involves contraction without movement. If you put your plams together and push one hand against the other, you can feel your arm muscles contracting. If both hands push equally, there will be no movement; this is isometric contraction. Such exercises will increase muscle tone and muscle strength but are not considered aerobic. Without movement, heart rate and breathing do not increase nearly as much as they would during an equally strenuous isotonic exercise.

Many of our actions involve both isotonic and isometric contractions. Pulling open a door requires isotonic contractions of arm muscles, but if he door is then held open for someone else, those contractions become ismetric. Picking up your books is isotonic; holding them in your arm is isometric. Both kinds of contraction are needed for even the simplest activities.