Isotonic: lso means 'same' and tonic means tension.In isotonic contraction muscles contract and shorten under a constant load throughout the entire range of joint. The shortening of a muscle's principle action (length of muscle decreases) is called concentric. The lengthening of the muscle (length increases) after contraction is called eccentric. Such types of contractions are commonly used in games and sports. This is also called dynamic contraction. In the initial phase of movement, concerned muscles are stretched and then they contract explosively. Because of shortening and lengthening of muscles there is always a resultant movement at concerned joint. In majority of the cases the dynamic muscle contraction is a specific combination of concentric and eccentric contractions. This happens in all explosive movements like jumps, throws, etc.
