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.

Adrenaline increases the "alertness" of the nervous system, meaning it's ready to trigger muscle contraction. It also increases the amount of blood flow and changes the tension of the muscles, which, ...

The flow of water within a muscle fiber may dictate how quickly muscle can contract, according to a new study. The flow of water within a muscle fiber may dictate how quickly muscle can contract, ...