A muscle consist of sarcomeres which can contract in three different ways, namely concentric, isometric and eccentric. But what is the difference in these types of muscle contraction?

-Isometric contraction (a): During an isometric muscle contraction the sarcomere produces force, but the length of the sarcomere and therefore the length of the muscle and the positions of the limbs does not change. Isometric contraction plays an important role in posture regulation or transferring forces or moments across joints. While the length of the sarcomere does not change, cross-bridges between actin and myosin filaments are constantly made and broken during an isometric contraction.

-Concentric contraction (b): a concentric contraction is the best know and means that the sarcomere shortens during contraction. The force delivered by the sarcomeres during shortening, causes the muscle to shorten and the affected joint(s) change position.

Three different types of muscle contraction

-Eccentric contraction (c): An eccentric contraction is a contraction in which the sarcomere delivers force against a greater external force and is thereby lengthened.

References:

-Wilmore, J.H., Costill, D.L., Kenney, W.L. (2008). Structure and function of exercising muscle. Physiology of Sport and Exercise Fourth Edition. USA Human Kinetics.