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.

Medically reviewed by Katrina Carter, DPT Key Takeaways Voluntary muscles can be controlled by the person, like muscles in your neck and legs. Involuntary muscles work without you thinking about it, ...

Visual feedback is just as important as a sense of body position when it comes to the involuntary reflexes that activate muscle movement, says a new study in the open-access journal eLife. The ...