Isotonic and isometric contraction ::
In common mans language the word contract means to get smaller however a muscle may not become always when it contracts in general there are two types of muscle contractions isotonic and isometric
1. An isotonic contraction results in decrease in the length of the muscle without changing the tension if one end of the muscle is attached to movable part its contraction moves that part the term isotonic comes from iso meaning same and tonic relating to tension while the length of the muscle is changing its tension remains the same
2. In isometric contraction on the other hand the length of the muscle remains the same (isometric = same measurement ) but its tension increases this can occur when both ends of the muscle are attached to immovable parts for example place your hands on the seat of your chair straighten your arms and then push down on the chair as hard as you can unless you were sitting in an extremely weak chair the seat did not move while you were pressing on it yet you were certainly expending energy and muscles of your arms were undergoing contraction
3. there is still a third type of peculiar muscle activity that is often disregarded muscle may also be active when they are actually lengthening this occurs while a muscle is paying out under the action of its antagonists to maintain control over the movement and protect the joint for example lift this book into the air and then slowly lay it down no the table extending your arm as the extensors in your arm contract the flexors lengthen but they still maintain a certain tension to produce a smooth flowing motion rather than a sudden drop the active lengthening of muscle is referred to as excentric action in contrast to the concentric action that occurs when the muscle shortens
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