Muscle contraction is the tightening, shortening, or lengthening of muscles when you do some activity. It can happen when you hold or pick up something, or when you stretch or exercise with weights.

There are two main phases of lifting weights: eccentric and concentric. The eccentric phase is where you lengthen the muscle, and the concentric phase is when you contract or shorten the muscle. While ...

This is a common strength training technique that involves manipulating the muscle lengthening portion of an exercise, usually by slowing down the movement. Share on Pinterest Getty Images/Eugenio ...