Exercise also releases endorphins, a natural painkiller, that give some people a 'high' when they exercise. It's estimated that men who take moderate exercise have a 17 per cent lower risk of Parkinson's disease than sedentary men.

Exercise stimulates the proliferation of blood vessels in the brain and increases the synaptic connections between brain cells, too.

Clinical trials have shown that exercise programmes can help people with depression, enabling them to reduce and even come off antidepressant drugs. People who take up exercise report feeling more alert. Certain types of exercise, yoga and tai chi for example, help to reduce anxiety.

Regular exercise lowers blood pressure and keeps the arteries healthy, therefore protecting against vascular dementia. Other studies have shown that 'super-fit' older people have very little cognitive decline. It is certainly a good insurance policy - if nothing else - to exercise for the sake of our brains as well as our hearts and muscles. A healthy diet is important too.