Your body's own painkillers
In the 1970s, John Hughes and Hans Kosterlitz at Aberdeen University discovered endorphins in the brain. Endorphins are our body's natural opiates, produced when we experience stress. Endorphin release from neurones increases during exercise and this is thought to promote a feeling of well-being. Endorphin release has also been linked with acupuncture, the traditional Chinese medical practice of inserting needles into the body to relieve pain.