Physical activity is important during childhood and drives many of the changes that help us grow into adults, but it also plays a major role as we get older; a loss of fitness may explain why some older people develop dementia. For example, one long term study showed that those who exercised more than twice a week during middle age were much less likely to develop dementia by the time they reached their 60s and 70s.
Increasingly, it looks as though exercise is not an option for us, as humans, but a necessary condition.
It's not just about feeling better in the short term - the warm glow that comes after exercise - there are important long term or permanent changes as well.
- The brain is one of the most energy hungry organs in the body and needs a healthy blood supply. Regular exercise improves the blood supply to the brain and reduces blood pressure, which protects against the damage that high blood pressure can cause.
- improved fitness cuts the risk of diabetes and obesity - these problems upset the insulin system in the brain and lead to a cycle of damage that contributes to Alzheimer's disease.
- exercise stimulates the release of neurotransmitters (these are chemicals that signal information around the brain and body) such as serotonin, noradrenaline and dopamine, which are the same ones that antidepressants work on
- exercise also prompts the brain to produce growth factors such as insulin-like growth factor-1 (IGF-1) and brain-derived neurotrophic factor (BDNF) which help your nerve cells flourish and encourage the formation of new connections between cells.
The US Department of Health is now encouraging children to exercise, and suggests 30 minutes a day for Primary School children, increasing to 45 minutes daily for Secondary pupils. "We need to have kids moving every day, not just because it makes sense health-wise, but because it raises test scores" says one of the doctors behind the research.
Exercise,though, has also been shown to sharpen the ageing brain and there is more evidence in favour of exercise than for cognitive training strategies, such as brain-teasers.
What kind of exercise?
Even gentle activity, such as a walk a few times a week, for sedentary volunteers was shown to increase brain connections and the size of an area of the brain called the hippocampus, which is involved in memory processes.
Even better may be high intensity interval training (HIIT) which consists of very short bursts of hard exercise. This stimulates the pituitary gland in the brain to release human growth hormone (HGH) which in turn enhances neurotransmitter levels. A German study showed that a group who exercised using HIIT approaches performed 20 % better in a brain test than a group who did more leisurely activity.
First time exercisers should build towards HIIT slowly, but the benefits of even leisurely exercise have been shown and can be enjoyed at any age.