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Boost your Mood with Daily Exercise

     Daily exercise is widely known to provide numerous health benefits, a notable one being an improved mood. The most popular explanation for this euphoric effect is the “opioid theory”. The opioid theory states that acute exercise causes the body to release a substance called beta-endorphin, a neurotransmitter that when bound to brain receptors increases feelings of happiness. Fortunately, for people who are chronically depressed, or in search of a way to elevate their mood, research exists to support the opioid theory and the use of exercise as a natural antidepressant.

For example, Boecker et al. tested the opioid theory by examining “the runner’s high”, a phenomenon in which running creates a state of happiness. In their study, the researchers measured the amount of endorphin binding in 10 males runners both before and after a two-hour endurance run. These measurements were then compared with the athletes’ moods as described on a mood rating scale. In accordance with the “opioid theory”, the results not only found the two-hour run to increase subject endorphin binding; endorphin binding was also found to be correlated with subject euphoria ratings; so that subjects with the most endorphin binding experienced the greatest sense of well-being. In addition, subject euphoria ratings more than doubled after the two hour run, suggesting that exercise plays a large role in mood regulation.

In fact, Koseoglu et al.  has even found exercise to have the potential for alleviating migraine headaches through its release of endorphins. In their study, 36 patients with regular migraine headaches were placed on a six-week exercise program. The program consisted of subjects performing aerobic exercise at 60% of maximal heart rate for 40 minutes three-days a week. As a consequence of the exercise training, patient endorphin levels were found to be elevated and to be negatively correlated with the number of migraine attacks. The exercise program also decreased the patient’s migraine intensity and duration.

With all the evidence supporting the “opioid theory,” the question remains: what exercise intensity elicits the greatest endorphin release? A study published by Rahkila et al. investigated this question by subjecting 19 healthy males to cycling exercises of various intensities ranging from 25% to 98% of VO2max for 8 minutes. Plasma endorphin levels were measured at all intensities, and it was found that there was no significant change in plasma endorphin concentrations below 75% VO2max. However, exercise intensities of 75% and 98% increased plasma endorphin concentrations by 48% and 305%, respectively - supporting the notion of a precipitous dose-response relationship between endorphin release and exercise intensities greater than 75%. Other studies have found comparable results, with exercise intensities above 50% VO2max leading to elevated endorphin levels. However, there appeared to be an inverse relationship between the amount of time each intensity of exercise needed be maintained before the endorphin levels significantly rose; the high the intensity of exercise, the shorter the time required before endorphin levels increase.

Furthermore, a study published in Medicine and Science in Sports and Exercise supports the finding that exercise duration plays a key role in the release of endorphins. In the study, the researchers measured plasma endorphin levels as a function of time for 12 males performing bicycle exercises at 70% and 80% of VO2max. As expected, endorphin levels rose for both intensities; however it took 15 minutes for a significant elevation of endorphin levels at the lower exercise intensity and only 5 minutes at the higher exercise intensity. Furthermore, examination of the blood after 30 minutes revealed even greater plasma endorphin content than at earlier time points. Clearly, exercise duration is an important factor to consider when optimizing endorphin release.

Based on these studies, it is clear that exercise can boost your mood by elevating plasma endorphin levels. More specifically, you will receive the greatest endorphin release, and psychological reward, when performing the longest and most difficult workouts in your training regimen. Finally, these studies provide us with the knowledge and tools to not only to trim our waist line, but to live a happier life.

Written by Michael Fox and Eric Sternlicht, Ph.D. - Department of Kinesiology,
Occidental College, Los Angeles, CA.