Not only does exercise improve your mood and enhance your self esteem, your brain loves physical exercise too. Exercise is now thought to promote the growth of new brain cells. Until recently, received wisdom had it that we are born with a full complement of neurons (brain cells) and produce no new ones during our lifetime. Fred Gage from the Salk Institute in La Jolla, California, broke that myth in 2000 when he showed that even adults can grow new brain cells. He also found that exercise is one of the best ways to achieve this.

Angela Balding from the University of Exeter, UK, found that schoolchildren who exercise three or four times a week get higher than average exam grades at age 10 or 11. The effect is strongest in boys, and while Balding admits that the link may not be causal, she suggests that aerobic exercise may boost mental powers by getting extra oxygen to your energy-guzzling brain.

Simply walking sedately for half an hour three times a week can improve abilities such as learning, memory and concentration. Senior citizens too who walk regularly perform better on memory tests than their sedentary peers. What's more, over several years their scores on a variety of cognitive tests show far less decline than those of non-walkers. Every extra mile a week has measurable benefits - on your thinking abilities and your physique.

In mice, at least, the brain-building effects of exercise are strongest in the hippocampus, which is involved with learning and memory. This also happens to be the brain region that is damaged by elevated levels of the stress hormone cortisol. So if you are feeling frazzled, it may do your brain a favour if you go for a run - or simply take a walk!