ENDORPHINS

Endorphins are neurohormone polypeptide molecules, synthesised by the hypothalamus of the brain and secreted into the bloodstream by the pituitary gland. There are four different types of endorphin produced in the body:

• Alpha
• Beta
• Gamma
• Sigma

Beta endorphins consist of 30 amino acid subunits and it is the beta endorphins which show the greatest increase in plasma concentration during times of exercise.

Endorphins are thought to be released from the pituitary during times of pain or stress. Studies have also looked into the affect of acidosis, caused by exercise, on endorphin release(2). Exercise induced acidosis of the blood appears when prolonged exercise has occurred and oxygen flow to the muscles has decreased. Anaerobic respiration occurs causing lactic acid accumulation, which results in acidosis. This acidosis is then thought to stimulate the pituitary to release the endorphins.

HOW DO ENDORPHINES IMPROVE OUR MOOD?

Endorphins are released into the bloodstream by the pituitary

Endorphines enter nociceptive afferents (nerons which carry pain implulses to the brain)

Endorphines then bind to opioid receptors in the neurons (mu, kappa, delta). These receptors are the same as the receptors which drugs like morphine bind to.

Endorphins have an antagonistic effect on the receptors and therefore block the release of neurotransmitter molecules from the nerve terminal.

NO PAIN SIGNALS REACH THE BRAIN!!!

The endorphins are therefore said to have an analgaesic effect.

By having this analgaesic effect on the body, endorphin release results in a state of euphoria. As well as reducing pain this also aids in the reduction of stress. Due to these effects, endorphins are known as the body's "natural painkillers". Because they have similar actions to opiate drugs they are also known as the endogenous opioids.

Other actions of endorphins include:

• Stimulation of the immune system by the activation of natural killer cells
• Postponement of aging.

HOW DOES EXCERCISE AFFECT ENDORPHIN RELEASE?

Blood levels of beta-endorphins have been found to increase to as much as five times their resting levels during a prolonged bout of aerobic exercise (over 30mins). This measurement varies from person to person and is affected by how much regular exercise you take part in.

As tolerance of the body to opioid drugs increases with increased use over time, the pattern of tolerance to endorphins follows a similar path(3). The more regularly you exercise, the higher the body's natural tolerance to endorphins. This means that as you exercise more, you require a higher intensity of exercise in order to produce the same endorphin release. As with opioid drugs, exercise can become addictive, as athletes begin to require the analgaesic effects of the endorphins. This analgaesic effect is sometimes referred to as "the runners high". Like any addiction, exercise addiction can result in dependence, tolerance, and continued use or participation despite adverse affects, leading to the sacrifice other activities to devote more time to exercise. The "runners high" is said to be experienced by 60-70% of well conditioned runners.

PSYCHOLOGICAL HYPOTHESES EXPLAINING HOW EXERCISE AFFECTS OUR MOOD

The Mastery Hypothesis

This states that exercise enhances mood because it triggers a sense of achievement(3). Mastering a new skill or being good at an old one makes us feel accomplished and may well have an affect on our mood.

The Distraction Hypothesis

This states that exercise alleviates depression by temporarily distracting us from the everyday stresses of our lives.

Social Interactions

Socialising with our peers often accompanies exercise eg. playing in a team. We may feel happier after exercise due to this social interaction rather than the actual effects of the exercise itself.

So......there are many possible explanations for the reasons why exercise affects our mood, making us feel happier in life. Whether the effects are physiological, psychological or a combination of both, we may never fully understand the reasons behind the exercise high.

Perhaps exercising affects everybody in different ways and we will never actually define one mechanism for the mood altering effects of exercise. Given all the physical benefits to exercise it does seem logical that it should also aid us mentally. Remember, "Healthy body, healthy mind!"

I really had to exercise. If not I'll be so depressed. Now I know why I'm so restless and so unhappy whenever I can't get to exercise. Went for a short swim today. It really cheered me up quite a bit. The swim did kinda help release some stress from my back actually.