Eccentric contraction

[BSHC]

Eccentric contraction

During an eccentric contraction, the muscle elongates while under tension due to an opposing force being greater than the force generated by the muscle. 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 repositioning of a load.

This can occur involuntarily (when attempting to move a weight too heavy for the muscle to lift) or voluntarily (when the muscle is 'smoothing out' a movement). Over the short-term, strength training involving both eccentric and concentric contractions appear to increase muscular strength more than training with concentric contractions alone.

During an eccentric contraction of the biceps muscle, the elbow starts the movement while bent and then straightens as the hand moves away from the shoulder.

During an eccentric contraction of the triceps muscle, the elbow starts the movement straight and then bends as the hand moves towards the shoulder.

Desmin, titin, and other z-line proteins are involved in eccentric contractions, but their mechanism is poorly understood in comparison to cross-bridge cycling in concentric contractions.

Muscles undergoing heavy eccentric loading suffer greater damage when overloaded (such as during muscle building or strength training exercise) as compared to concentric loading.

When eccentric contractions are used in weight training, they are normally called negatives. During a concentric contraction, muscle fibers slide across each other, pulling the Z-lines together.

During an eccentric contraction, the filaments slide past each other the opposite way, though the actual movement of the myosin heads during an eccentric contraction is not known.

Exercise featuring a heavy eccentric load can actually support a greater weight (muscles are approximately 10% stronger during eccentric contractions than during concentric contractions) and also results in greater muscular damage and delayed onset muscle soreness one to two days after training.

Exercise that incorporates both eccentric and concentric muscular contractions (i.e. involving a strong contraction and a controlled lowering of the weight) can produce greater gains in strength than concentric contractions alone. While unaccustomed heavy eccentric contractions can easily lead to overtraining, moderate training may confer protection against injury.

 Eccentric contractions in movement

Eccentric contractions normally occur as a braking force in opposition to a concentric contraction to protect joints from damage.

During virtually any routine movement, eccentric contractions assist in keeping motions smooth, but can also slow rapid movements such as a punch or throw.

Part of training for rapid movements such as pitching during baseball involves reducing eccentric braking allowing a greater power to be developed throughout the movement.

Eccentric contractions are being researched for their ability to speed rehab of weak or injured tendons. Achilles tendinitis has been shown to benefit from high-load eccentric contractions.

 ==============

Eccentric contraction

When you curl your arm, the movement is "concentric," which means a shortening under contraction of the target muscle, the biceps.

When you straighten your arm from the curl position, the movement is "eccentric," which is a lengthening of the biceps muscle while contracting.

Some weight training advocates say that specific eccentric training can help build muscle size and strength superior to results from standard concentric-eccentric movements.

A justification for this is that eccentric muscle contraction is stronger than concentric contraction, which allows you to enlist heavier weights. To accomplish this, you may need to employ a helper or spotter to assist with the concentric part of the lift, and then you do the eccentric part alone.

Muscle soreness after a workout may be increased with a greater volume of eccentric work.

The negative or lowering phase of an isotonic contraction—also called negative curls. An example would be the lowering phase of a bicep curl.
What some people don't know is that it's the eccentric contraction that often causes muscle soreness because, as you lower the weight, your muscle is actually stretching at the same time they are contracting. This can result in muscle soreness, but it's a temporary soreness that should go away in a few days after exercise.

An eccentric contraction occurs when a muscle is contracting, and an external force is trying to lengthen the muscle. The classic mechanism for a muscle strain is an eccentric contraction.
An eccentric contraction is also a type of strengthening exercise for a muscle, when performed in a controlled manner. Physical therapists and strength trainers often use eccentric exercises when strengthening muscles. Eccentric strengthening is often used to treat chonic tendon and muscle injuries.

Eccentric contractions are the common cause of injuries such as a groin pull or hamstring strain.

 In Pilates we use all three kinds of muscle contractions: eccentric, concentric, and isometric where the muscle is held in a static contraction. But in Pilates, there is more emphasis on the eccentric contraction than one finds in most exercise systems. It is the eccentric contraction that accounts for the long, strong muscles Pilates is known for.

In an eccentric contraction a muscle lengthens as it resists a force. Contrast that image with what we usually think of as a muscle contraction, the concentric contraction, where a muscle shortens as it overcomes a weight or force. It is shortening muscle that gives a more contracted or bulky look to the muscles.
Pilates uses resistance to the springs on the large equipment like the reformer, chair, or tower; resistance to gravity; and resistance to the spring-like action of small equipment like the magic circle or exercise band to train the muscles in eccentric contraction.

Let's look at some examples of eccentric contractions from the Pilates mat exercises. On the mat it is mainly resistance to gravity that creates eccentric contractions. Examples would be the roll down part of the roll up or roll over, where we intentionally control the roll down, lengthening the torso against the pull of gravity. Another example from the mat work would be the challenge to the chest and biceps in the slow, controlled downward moving part of the push up.

When you resist the springs on Pilates apparatus, or use the magic circle or exercise band, the lengthening contraction often happens when you resist what you might think of as the return portion of the exercise. For example, with the magic circle, you squeeze it which is usually a concentric contraction; but then you control the release which becomes a muscle lengthening eccentric contraction. Or, think of the exercise band. If you stand on it to fix the middle, and pull the two ends up, that part is a concentric contraction for the biceps. When you resist the pull of the band as you let it down slowly, that is the eccentric contraction for the bicep.

It is the eccentric contraction that puts the strength in our length. What I mean is that eccentric contractions are very challenging for the muscles. They do a good job of stressing the muscles. Being stressed, and then rebuilding stronger, is how muscles build strength.

Eccentric contractions are the subject of a lot of study because it is thought that muscle strengthening might be greatest with exercises that include eccentric contraction . Because of the higher level of tensile stress that eccentric contractions create, eccentric contractions are associated with muscle soreness, and injuries like strains and tears. However, this is rarely an issue in Pilates where control is emphasized, and we don't overload the muscles.

Finally, no discussion of Pilates and the eccentric contraction would be complete without mentioning the role of the mind, and intention, in Pilates exercise. In Pilates, we actively intend length in our movement. Of course we set the stage for that with the right exercise instructions, alignment, and equipment. But ultimately Pilates moves are meant to be practiced with an attentive mind. When the mind is focused on length, all the subtle core moves that help create successful, and careful, eccentric contractions can take place

* virtus "excellence, potency, efficacy," lit. "manliness, manhood"