Muscles work by pulling on the bones they are attached to. They never push. For this reason, they are only able to exert force in one direction in most circumstances. They are able to contract (think about biceps curls) and relax (lowering the weight after curling 350lbs! Just kidding…) Muscles are, however, under tension even when lowering the weight. If you think about pulling on a rubber band you are adding force to pull it apart. If you slowly move that rubber band back to the starting position, you are adding force to it while it is moving. That is eccentric work.
Eccentric work in muscles and tendons has been shown to increase blood flow, and is related to the concept to time under tension. The higher time under tension, the higher the rehab potential.
When performing exercises in a rehab setting, eccentric loading is used to improve tendon and musculotendinous healing. It is very useful when just starting out rehab for a specific injury as it allows the muscle and tendon maximum time under tension without increased risk for injury.
Tendon Injuries
Force across a tendon from eccentric exercise also affects the tendon on a physiological level. There is a term called mechanotransduction, which is a fancy way of saying the cells of a tendon turn exercise into cellular signals. These signals cause the tendon to adapt its structure and form. The more signals you add to the tendon through exercise, the stronger the tendon will be at the end of rehabilitation. Though the exact amount of time and exercise for optimal tendon repair remains unclear, it is still an important factor when dealing with a tendon issue.
Muscle Strength
After injuries, it is common for some muscles to be weaker than pre-injury, that’s where eccentric exercise comes in. Eccentric exercise has a unique benefit of providing a high force production with a relatively low energy cost. This can mean faster results for regaining strength, with a low risk of injury.
As you can see, eccentric exercise can provide many benefits from those that are recovering from injury. It can help injured structures remodel to a stronger and healthier state. There is one downside to eccentric exercise though, the connection with an inflammatory response. Eccentric exercise has been linked to higher rates of DOMS or delayed onset muscle soreness. For this reason it is important to correctly dose the type and amount of eccentric exercises done for each specific body part. Comment below if you would like me to dive deeper into a specific injury or body part that may benefit from eccentric exercises!
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