There are many different ways to exercise. Exercise can be divided into several categories. Isotonic activities are those where there is a range of motion employed to move a muscle group. There is a force exerted on the muscles that are maneuvered by contractions. Within this range of isotonic tensions are concentric and eccentric contractions. Concentric contractions are the most common. They occur when muscles are shortened and move across the joint attachment as force. An example of this is curling a dumbbell. When you extend the dumbbell to lower it, there is an eccentric contraction, which is the lengthening of the biceps. Even though it is lengthening there is still a contraction to control the free fall of the barbell against gravity.

Most exercises fall into the anaerobic category of exercise as opposed to aerobic. Anaerobic are repetitive motions like weight lifting that deal with fast-twitch muscle fibers. Anaerobic exercises tend to fatigue muscle because it quickly uses up the oxygen stores and replaces it with a metabolic by-product called lactic acid that causes cramping and soreness. Aerobic exercise deals with slow-twitch fibers. Fatigue of muscle with this type of activity comes from the consumption of the glucose energy stored for the muscles. They then tire because there is no more energy for them as when distance runners hit “the wall.”

Isometrics, however, are exercises where you contract muscles without shortening the muscle. Imagine holding a weight at arm's length. The muscle contracting to hold that object in that specific location is an example of isometrics. Isometric contractions build muscle strength and mass over a shorter period of time and effort. Contractions lasting for only ten seconds produce enough contractile tension over time to increase strength. Overall, isometric exercise is the preferred method for both toning muscles and losing weight. There is no danger of injury, exertion is lessened and time is saved.