THE 3 DIFFERENT TYPES OF MUSCLE CONTRACTIONS: Whether you're looking to build lean muscle, lose weight or increase your strength levels, there are 3 different muscle contractions that you can generate: Concentric Contraction: when the muscle is actively shortening. This typically happens on the initial lift of an exercise. An example would be the "pushing" movement. Eccentric Contraction: when the muscle is actively lengthening. This generally occurs on the negative portion of each rep.