An Overview of Eccentric Muscle Contraction

The Aims and Benefits of Negative Work

Female hiker jumping downhill
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When you think about muscle contractions, most people will assume this to mean a concentric contraction, such a biceps curl, in which the muscle simultaneously contracts and shortens.

There is another type of contraction in which the muscle lengthens as it contracts. This is called an eccentric muscle contraction. Eccentric contractions occur when a muscle opposes a stronger force and reverse its initial trajectory. Eccentric contractions are sometimes referred to as braking contractions, negative work, or simply "negatives."

Examples

Eccentric contractions are essentially the yin to concentric contractions' yang. The two work in tandem to build muscle mass and strength. Although concentric contractions are effective in triggering muscle growth, the controlled use of both concentric and eccentric contractions can ensure greater, all-around strength by stabilizing the muscles in and around a joint.

Eccentric contractions generally involve a lowering or releasing movement, while concentric contractions generally infer lifting or rising. For example, when you lift a barbell, you are using concentric contractions; as you lower it, eccentric contractions are at play.

Movements that employ eccentric contractions include walking down stairs, running downhill, lowering weights, and the downward motion of squats, push-ups or pull-ups.

Biomechanics

When used in medicine, the term "eccentric" means "away from the center." This is an apt way to describe when a muscle is both activated and lengthened.

During an eccentric contraction, the muscle will be challenged by an opposing force, such as a heavy weight or gravity. Even though the muscle is able to oppose the force, it will accede to it but do so in a way in that the muscle remains tense.

Eccentric contractions are not the same thing as "dropping" a weight after lifting it. It is a controlled movement in which you move toward an opposing force rather away from it.

Even as you walk down steps, you are placing stress on your muscles that allow them to grow even if you are not using all that much energy.

Negative Work

Eccentric muscle contraction produces negative work. Negative work is the force used to reverse a muscle from its initial trajectory. Since concentric contractions are the primary means of muscle growth (and, hence, are referred to as positive work), eccentric contractions are those that return the muscle to its starting point (negative work).

When a load exceeds the force of a muscle at its full length, the exercise is referred to negative because the muscle is absorbing rather than utilizing energy.

In physics, this is referred to as strain energy. This occurs when the stretched muscle absorbs the mechanical energy and converts it into what is known as elastic recoil.

Elastic recoil is energy that can be used for the next movement. For example, if you are doing squats, the lifting (concentric) phase utilizes energy, while the squatting (eccentric) phase absorbs energy and potentiates the next concentric movement. It is not dissimilar to the action of springs in which absorbed energy is converted into kinetic energy.

Running in another example. When running, mechanical energy is absorbed every time your foot strikes the ground and will continue as your body overtakes your foot. At that movement, elastic recoil energy is at its maximum and is readily transferred to the next stride, propelling you forward.

Depending on your pace, this can create the illusion that you are using less energy despite applying more force.

Benefits

Eccentric exercise can rapidly condition and build muscles. Hiking downhill for the first time, for example, can cause pain in the quadriceps, especially the next day. But it only takes a few more outings for the muscles and tendons to become stronger and less prone to soreness.

This is because of eccentric contractions, while functionally "easier," requires more force. It is this increased force that allows you to push harder on the concentric contractions. While eccentric exercise is more likely to cause delayed onset muscle soreness (DOMS), repeating the exercise a week or so later will invariably decrease DOMS symptoms.

Eccentric exercises are also protective in that they reduce muscle and tendon strain compared to concentric exercises.

By affording equal attention to each type of contraction, you can reduce your risk of injury or re-injury.

Athletic training commonly uses plyometrics and eccentric exercises to build muscle strength and endurance. Running, sprinting, jumping, hopping, and throwing a ball all use eccentric contraction to deliver power.

Pilates exercises also often employ eccentric contractions, resisting the springs in the reformer or gravity in body weight mat workout. Eccentric exercises are commonly used in rehabilitation, such as for ACL tears and injuries.

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