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.

Stimulating muscle fibers with magnets causes them to grow in the same direction, aligning muscle cells within tissue, Massachusetts Institute of Technology (MIT) and Boston University investigators ...

When labor begins, the uterus must coordinate rhythmic, well-timed contractions to deliver the baby safely. While hormones such as progesterone and oxytocin are key contributors to that process, ...