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.

More than 30 rare muscular dystrophy types cause progressive muscle weakness from inherited gene mutations. Combined, they affect about 1 in 5,000 to 8,000 people. Common subtypes vary by age of onset ...

The back consists of large, complex muscles that support your trunk and spine. There are many types of back muscles, and they are all essential, helping you walk, bend, twist, and hold your body ...