Benefits to the heart and arteries

The first key point in our case for exercise is that it benefits the heart by making it stronger, thus reducing the risk of coronary heart disease. Arteries benefit by becoming more elastic, expanding and letting more blood through. The risk of blood clots and clogged-up arteries (atherosclerosis) is also reduced.

High blood pressure is a major risk factor for heart disease, stroke and other serious illnesses. Blood pressure can be kept under control by exercise: better blood circulation means less swollen ankles (oedema) and cold at extremities (hands and feet).

When our heart and arteries (cardiovascular system) are working efficiently they are making oxygen and nutrients available to muscles, bone and brain cells where they have important jobs to do.

Muscle strength and bone density

Secondly, exercise is vital to maintain muscle strength and bone density, which decline naturally as we age. Muscle strength is vital to perform daily activities such as getting out of the bath or a chair. With inactivity, muscle quickly wastes away; after only two weeks in bed recovering from, say, flu, we can lose 1 - 2 per cent of bone density and up to 20 per cent of our strength.

Muscle weakness round the major joints can lead to osteoarthritis, a painful condition affecting the cartilage and bone. Thinning bones - osteoporosis - is painful, disabling and a major cause of fractures in the wrist, hip and spine. Exercise stimulates the production of growth hormone which helps to maintain muscle and bone. Outdoor exercise tops up levels of vitamin D (from sunshine) which is also vital for bone health.

People who have a condition such as osteoarthritis can eliminate the pain this brings by building muscle strength around the affected joint. Exercise can prevent falls, a major threat to people in the oldest age groups. It helps to regulate our metabolism all the chemical and physical processes that enable us to function), controlling our weight and reducing the risk of late onset diabetes. Many diabetics can keep their condition under control with regular exercise and a good diet.

The immune system

Our immune system benefits enormously from exercise, although exactly how is not fully understood. An efficient immune system doesn't just ward off colds and flu - it may even lower our risk of many cancers, including cancers of the colon, breast, uterus, ovaries, prostate gland, testes and lung (even in smokers).

Exercise helps to keep our brains healthy. Only four arteries supply blood to the brain so arterial health and avoiding blood clots is vital to prevent strokes and vascular dementia and even preserve our memories and understanding. Exercise improves our mood by releasing endorphins from the brain. Stress, anxiety and some types of depression can be helped by exercise, which also improves the duration and quality of sleep. Exercise can also bring many social benefits, such as new friendships and fun, which in turn improve well-being.