What is the term for when a muscle contracts and shortens?

The term for when a muscle contracts and shortens is known as concentric action. This type of muscle contraction is characterized by the active shortening of the muscle fibers as they generate force. During concentric contraction, the muscle overcomes an external resistance, such as when lifting a weight or moving a body part against gravity.

For instance, when performing a bicep curl, as you lift the weight toward your shoulder, the biceps muscle contracts concentrically to produce movement, resulting in a shortening of the muscle. This is essential for various physical activities and plays a crucial role in exercises aimed at building strength and muscle mass.

In contrast to concentric action, eccentric action involves the muscle lengthening while still under tension, such as when lowering a weight. Isometric action occurs when the muscle generates force without changing its length, meaning there is no movement at the joint. Static action, while less commonly used as a specific term in exercise science, generally refers to motions or positions that do not involve movement. Thus, understanding concentric action is vital for recognizing how muscles contribute to movement in fitness and sports.