Eccentric Contraction: When a given resistance overcomes
the muscle tension so that the muscle actually lengthens the muscle
is said to be in eccentric contraction. Although the contracting
muscle develops tension, it is overpowered by resistance. When you
slowly lower a curled weight from the shoulder, the biceps muscle
contracts eccentrically. If the biceps was relaxed, gravity would
extend the elbow joint and lower the weight with considerable
speed. Slowing the movement against resistance provides an
additional muscle - developing factor.