Exercise stimulates the release of various chemicals within the brain and the 'endorphin high' which many runners experience as the brain releases opiate-like chemicals which the body uses as natural pain relievers is well documented.

The brain also produces a number of neuro-transmitters such as serotonin, dopamine and norepinephrine, all of which have beneficial effects as mood elevators. Once again, the effect of low levels of these is well documented as leading to depression, anxiety and sometimes even aggression.

In addition to stimulating the brain into producing chemicals that are helpful in reducing stress, exercise also reduces the production of chemicals that result from stress. When an individual is under stress the sympathetic nervous system produces chemicals such as cortisol and hormones which, if left in the blood stream, can harm the blood vessels, producing scaring and even leading to narrowing of the arteries.

Exercise can help to solve this problem in two ways. First, a good workout will actually make use of those compounds and break them down into harmless products that are passed out in the urine. Second, exercise helps to strengthen the blood vessels and give them greater elasticity so that they are able to withstand attack better.

One of the more common effects of stress is to produce tense muscles, particularly in the neck, shoulders and calves and exercise can help loosen these up.

There are also a number of psychological benefits to be derived from a regular exercise routine. Focusing on an exercise routine takes your mind away from whatever may be causing the stress in your life and it's surprisingly difficult to concentrate on whatever is worrying you and your workout at the same time.

This effect also helps to give your mind a chance to bring about what is known as homeostasis. This is a feedback mechanism within the body which acts to bring you back to a state of equilibrium and a strenuous workout which takes your mind off your problems gives this system time to function.

Of course there are other psychological benefits which follow on from a regular workout such as the self-confidence that can be gained from simply improving your overall health and fitness. It's a case of 'when you look good, you often feel good'. In addition, it helps to realize that you are exerting effort to improve your mind and body and are doing something positive rather than giving in to the feelings of helplessness and the resultant passivity that frequently accompany stress.