What type of contraction is landing from a jump?

A weird bit of muscle physiology

tap to expand

An eccentric or braking contraction is an interesting but routine type of muscular contraction that seems like a paradox: the muscle is contracting even as it is lengthening! It is the yang to the yin of concentric contraction. Eccentric contraction is a bit physiologically mysterious, and is known to be harder on muscle, causing more soreness (quadriceps after hiking down a mountain is the classic example). It may be a good stimulus for adaptation in tendon as well as muscle. However, just because it is a little harder on muscle does not make it ‘better exercise’ or a reason to run downhill rather than up.

When you think of a muscle contraction, you usually think of a muscle getting shorter, which is called “concentric” contraction — but that’s not always what happens. We can also do “isometric” contractions, in which there’s no change in length, AKA “clenching.” And then there’s the weird one, a mysterious but routine bit of muscle trickery known as “eccentric” contraction, and it is odd indeed: contraction while lengthening, also sometimes called a braking contraction.

How is this possible? How can that even be called a “contraction”?1 Good question! This is one of the classic examples of a small but persistent mystery of biology. In this age of science fiction body scans and custom-built medicinal molecules, no one really knows quite how eccentric contraction works. The theory of muscle contraction — the sarcomere model, more on this below — is impressive but inadequate.

What is an eccentric contraction used for?

Even if no one knows how it works, it’s easy to understand why you need eccentric contraction: we regularly need to control, slow-down the lengthening of a muscle, a “braking” contraction.

Not literally, of course. 0–5 items/week depending on coffee intake & most posts are very short. Subscribe now or follow on Twitter or Facebook. Browse the archives. ❐