An eccentric muscle contraction (lengthening) occurs when a force applied to the muscle exceeds the momentary force produced by the muscle itself. This will result in forced lengthening of the muscle-tendon system during contraction (the muscle is forced to lengthen due to the high external load). During this process, the muscle absorbs the energy developed by an external load, which is why eccentric action is also called “negative work” as opposed to concentric contraction (shortening) or “positive work.” Repeated eccentric muscle contraction during exercise contributes to microscopic damage to muscles and tendons, leading to chronic muscle strains, muscle rupture, and tendinopathy.
Skeletal muscles contract eccentrically to support body weight against gravity in anticipation of absorbing shock or to store elastic recoil energy for concentric (or accelerated) contractions.
Eccentric contractions are slow and elongated, aimed at a specific muscle. For example, during a slow lowering to sit in a chair, the movement is an eccentric, or “negative” contraction.
The tibialis anterior contracts eccentrically to control the lowering of the foot after being on the ball of the foot. This allows the foot to gently lower to the ground and gradually accept the body weight. Without this intervention of the tibialis anterior, the foot will “hit” the ground at initial contact.
There are three ways that a muscle can be injured:
- Intense
- Over a long period
- Eccentric.
- The micro-injury presents with small lesions in the muscle fiber.
- The micro-injury presents with small lesions in the muscle fiber.
- Swelling (swelling)
- Possible anatomical deformation
- Joint dysfunction
The muscles most at risk of fatigue are the muscles:
- With two joints (biarticular)
- Extension at the hip joint with flexion at the knee joint makes the rectus femoris very vulnerable to injury.
- Limited range of movement
- Eccentric