Isometric v Isotonic Contractions

An isometric contraction is where a muscle contracts but the length of the muscle does not change (therefore it doesn’t move). Sporting examples could include a rugby scrum or leaning back and holding in a tug of war.

An isotonic contraction is where a muscle contracts and movement is present. There are two types of isotonic muscular contraction:
Eccentric contractions occur when the muscle lengthen due to a greater opposing force.
Concentric contractions occur when the muscle shortens, therefore generating force.