The muscle act in three major ways of contraction where there are the concentric, eccentric, and isometric actions. The nerve musculoskeletal control system of the muscle is a mixed system of a length-control system which uses the muscle spindle and a tension-control system which uses the tendon organ. (Faulkner, John A. et al., 2007)

Concentric contractions occur when a muscle develops sufficient muscle tension to overcome a resistance or load. The muscle shortens visibly in order to move a body part. An example is during the up phase of a pushup where the elbow extensors contract concentrically to extend the elbow. Concentric contractions may be isokinetic or isotonic.

Isokinetic exercise attempts to combine the best features of both isometrics and weight training. It provides muscular overload at a constant preset speed while a muscle mobilizes its force through the full range of motion. During isokinetic contractions, muscle shortens at constant speed or constant angular velocity over the full range of motion. During a full isokinetic contraction, the tension developed by a muscle is at its maximum throughout its whole range.

In order to perform a controlled isokinetic contraction, special equipment is needed which contains a speed governor so that the speed of movement remains constant regardless of how much tension is produced by the contracting muscle. For instance, an isokinetic stationary bicycle which is set at 120 revolutions per minute means that no matter how hard and fast the athlete works, the isokinetic properties of the bicycle will allow the athlete to pedal only as fast as 120 revolutions per minute.

It is thought that training that uses isokinetic contractions is able to increase the blood supply to skeletal and cardiac muscle, and hence improves muscle strength, endurance, and cardiac fitness. Since high muscle tensions are exerted at each phase of movement, isokinetic contractions strengthen the whole muscle.

In addition, isokinetic exercises can be designed to mimic the actual speeds of sports-specific activities. This is thought to also improve the neuromuscular coordination so that more muscle fibres can be recruited and muscles can contract more efficiently. The major disadvantages of isokinetic exercises are that they can only be performed properly on machines which are usually expensive, and the types of movement that can be performed are rather limited. Hence, it may not provide the full range of sports-specific movements available.

Isotonic contractions involve the muscle in a situation where equal amount of tension is being developed in the muscle throughout the exercise. The muscle develops equal tension while the muscle length changes. Such examples are pull-ups, push-ups and lighting weights.

Isotonic exercises are especially beneficial for developing strength and cardiovascular endurance. However, the major disadvantage is that the efficiency of joints varies with joint angles and thus, unlike the isokinetic contractions, a fixed resistance may not provide a sufficient workload over the complete range of motion to provide the maximum training benefits.

Eccentric contraction causes a muscle to lengthen under tension. Such contractions are used to resist external forces such as gravity. The quadriceps muscles, for instance, undergo eccentric contractions when a person walks down steps, runs downhill, or lowers a weight. Eccentric contractions also occur during the deceleration phases of running. The downward phase of a biceps curl, for example, requires eccentric action of the biceps muscle.

Training in which eccentric contractions predominate tends to cause significantly greater muscle soreness than other forms of training, although it may protect against future muscle soreness. In these training, strong muscle fibres may replace the weak ones, and neuromuscular coordination can improve, so that forces are distributed more effectively.

In order to get the maximum benefit from weight training using eccentric contractions, the weights must be lowered slowly and in a controlled manner either using spotters or machines. Another example is the plyometric press up where the athlete uses their own body weight as the resistance against gravity.

Isometric contraction is usually done when the joint or position of the limb is held in a fixed angular position. The muscle develops tension but there is no change in the length of the muscle. Isometric contractions occur when a rugby front row forward pushes against opponents in a static scrum, when American footballers perform a block tackle, or when a weight-lifter holds a barbell above his head for a few seconds. Exercises involving isometric contractions are especially good for developing strength, but it is not good for developing cardiovascular fitness. (McArdle, W. D. et al., 2007)