Asked by: Peter Turner, via emailNot only does stretching clear your mind by allowing you to focus on your body, it also releases endorphins. Blood flow to the muscles increases after a long stretch. Muscles are controlled by the nervous system, which has two main components: ‘sympathetic’ (fight or flight) and ‘parasympathetic’ (rest and digest). Static stretching increases activity in the parasympathetic nervous system, promoting relaxation. Although the heart rate may rise during a stretch, it tends to decrease after. Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.