Eccentric Training

An eccentric contraction is the motion of an active muscle while it is lengthening under load. Eccentric training is repetitively doing eccentric muscle contractions. For example, in a biceps curl the action of lowering the dumbbell back down from the lift is the eccentric phase of that exercise — as long as the dumbbell is lowered slowly rather than letting it drop (i.e., the biceps are in a state of contraction to control the rate of descent of the dumbbell).

An eccentric contraction is one of the three distinct phases in the movement of muscles and tendons, the other two are an isometric contraction (no movement), and a concentric contraction (contracting).

Eccentric training focuses on slowing down the elongation of the muscle process in order to challenge the muscles, which can lead to stronger muscles, faster muscle repair and increasing metabolic rate.

Eccentric movement provides a braking mechanism for muscle and tendon groups that are experiencing concentric movement to protect joints from damage as the contraction is released.

Eccentric training is particularly good for casual and high performance athletes or the elderly and patients looking to rehabilitate certain muscles and tendons.

This movement has also been described as negative training. This "negative" movement is necessary to reverse the muscle from its initial trajectory.

When weight exceeds the force developed by the muscle, as in an eccentric muscle action, the exercise is referred to as negative work because the muscle is absorbing energy in this loaded position.

Eccentric contractions use less energy, even though they create more force than concentric actions.

Adolf Fick originally discovered in 1882 that "contracting muscle under stretch could produce greater force than a shortening muscle contraction" like in concentric movements. Fifty years later, A.V. Hill determined that "the body had lower energy demand during an eccentric muscle contraction than during a concentric muscle action".

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Wikipedia