concentric

samankeskinen puhekieltä Having a common center.
puhekieltä (of a motion) in the direction of contraction of a muscle. (E.g. extension of the lower arm via the elbow joint while contracting the triceps and other elbow extensor muscles; closing of the jaw while flexing the masseter).

Antonym: eccentric. Concentric and eccentric movements are collectively referred to as isotonic (with motion), the antonym of which is isometric (without motion).