The type of exercise performed also depends on the individual's goals. Those who seek to increase their performance in sports would focus mostly on compound exercises, with isolation exercises being used to strengthen just those muscles that are holding the athlete back. Similarly, a powerlifter would focus on the specific compound exercises that are performed at powerlifting competitions. However, those who seek to improve the look of their body without necessarily maximizing their strength gains  would put more of an emphasis on isolation exercises.

One limitation of many free weight exercises and exercise machines is that the muscle is working maximally against gravity during only a small portion of the lift. Some exercise-specific machines feature an oval cam  which varies the resistance so that the resistance, and the muscle force required, remains constant throughout the full range of motion of the exercise.type of exercise has its uses. Compound exercises build the basic strength that is needed to perform everyday pushing, pulling and lifting activities.

These terms combine the prefix iso with tonic and metric . In isotonic exercises the force applied to the muscle does not change, and in  isometric exercises the length of the muscle does not change.

Weight training is primarily an isotonic form of exercise, because the muscles are used to push or pull weighted objects. Any object can be used for weight training, but dumbbells, barbells and other specialised equipment are normally used because they can be adjusted to specific weights, and are easily gripped. However, some exercises are not strictly isotonic because the force on the muscle varies as the joint moves through its range of motion, even though the force of the exercise remains constant.

Some forms of weight training use isometric contractions to further stress the muscles after or during a period of isotonic exercise. In this case the muscles flex and hold a stationary position, and no movement of a load takes place.

Another form of training that often uses weights has a different goal. Plyometric exercises exploit the stretch-shortening cycle of muscles to enhance the myotatic reflex. This involves rapid alternation of lengthening and shortening of muscle fibers against a resistance. The resistance involved is often a weighted object such as a medicine ball, but can also be the body itself as in jumping exercises. Plyometrics is used to develop explosive speed, and focuses on power instead of maximal strength, and may be used to improve the effectiveness of a boxer's punch, for example, or to increase the vertical jumping ability of a basketball player.

Compound exercises work several muscle groups at once, and include movement around two or more joints. For example, in the leg press movement occurs around the hip, knee and ankle joints. This exercise is primarily used to develop the quadriceps, but it also involves the hamstrings, glutes and calves.Compound exercises are generally similar to the ways that people naturally push, pull and lift objects, whereas isolation exercises often feel a little unnatural.

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