Monday, 25 November 2019

Unravelling the types of muscular contraction.

When a muscle contracts it generates a force.
In injury prevention we typically begin with isometric contractions; but what are they?

  • Isometric contractions generate force without changing the length of the muscle.  (a)  An example is when the muscles of the hand and forearm grip an object; the joints of the hand do not move, but muscles generate sufficient force to prevent the object from being dropped.

  • Isotonic contractions generate force by changing the length of the muscle and can be concentric contractions or eccentric contractions.  (b and c)

b) Concentric contractions cause muscles to shorten, thereby generating force and changing the angle of the joint. For instance, a concentric contraction of the biceps would cause the arm to bend at the elbow as the hand moves from near to the leg to close to the shoulder (a biceps curl)

c) Eccentric contractions cause muscles to elongate in response to a greater opposing force. Rather than working to pull a joint in the direction of the muscle contraction, the muscle acts to decelerate the joint at the end of a movement or otherwise control the re-positioning of a load.