Is there something built into the body or brain that drives us to exercise? A kind of built-in survival mechanism? Some research indicates that such a system does exist in the brain. Exercise is known to elevate mood in people of all ages, an effect that lasts an average of three to four hours. As a result, rates of depression are markedly lower in people who engage in frequent exercise.
As to what causes this, studies have pointed to an increased release of natural mood-elevating chemicals in the brain. Higher-intensity exercise leads to an increased release of a painkilling substance called beta-endorphin. Besides mitigating pain, beta-endorphin was also thought to improve mood and ease depression.
Further research, however, cast doubt on whether beta-endorphin was the sole mediator of the beneficial mental effects associated with exercise. Some of the reasons for such doubts are:
‘ While endorphin levels are elevated during and after exercise, they don’t always correlate with mood.1
‘ When drugs such as naloxone, which block the effects of beta-endorphin and other brain opioids, are given to people before exercise, the mood elevation persists, indicating that the elevated mood resulting from exercise must be due to something else besides endorphins.2
‘ The mood elevation of exercise lasts at least three to four hours and as long as 24 hours, while the increase in blood plasma levels of beta-endorphin lasts for only 15 to 60 minutes.3
A more likely explanation for the euphoric effects of exercise is that beta-endorphin acts to prime the release of various brain neurotransmitters, which results in an elevated mood and feeling of well-being.4 The brain neurotransmitters include dopamine, norepinephrine, serotonin, GABA and glutamate. That makes sense, since most antidepressant drugs work by elevating many of the same chemicals in the brain. Another example is that the euphoria associated with drugs such as cocaine is based on the drugs’ ability to elevate dopamine in the brain.
How important is all that? One researcher believes it’s nothing less than essential to the existence of the human race. He notes, ‘The brain stimulates humans to be physically trained. Physical exercise improves psychological condition. Physically strong people are also strong emotionally. Obviously, people who are physically and emotionally strong have a better chance to survive and produce offspring. I suggest that the endogenous euphoric reward system that reinforces physical training is one of the most important mechanisms for mankind’s survival.’ IM
1 Young, R.R. (1996). The acute effects of exercise on mood state. J Psychosom Research. 40:123-141.
2 Janal, M.N., et al. (1984). Pain sensitivity, mood, and plasma endocrine levels in man following long-distance running: effects of naloxone. Pain. 19:13-25.
3 Sforzo, G.A. (1989). Opioids and exercise: an update. Sports Medicine. 7:109-124.
4 Sher, L. (1998). The endogenous euphoric reward system that reinforces physical training: a mechanism for mankind’s survival. Medical Hypotheses. 51:449-50.