Runner's High: Is It for Real? (cont.)

"For a long time, people believed the answer lay within the whole endorphin argument -- with long-duration exercise you release endorphins, which have a morphine-like effect on the body and therefore may be responsible for the feelings of well-being," Bryant tells WebMD.

While it's a good theory, Bryant explains, it doesn't necessarily hold water.

"While our circular levels of endorphins might be up, whether that impacts a person's psychological outlook output directly is probably not that likely," says Bryant. "In some studies, when the effects of endorphins have been blocked chemically, people have still experienced this high, so the whole endorphin argument has been called into question."

With endorphins largely out of the picture, researchers have looked at other types of neurotransmitters that might have a role in affecting a person's mood.

"Norepinephrine secretion, dopamine, and serotonin have all been shown to help to reduce depression," says Bryant. "These neurotransmitters also tend to be released and produced in higher concentrations during exercise, so people think that it may be some of these other biochemical substances, aside from the endorphins, that might be responsible for this effect."

Another theory that is tossed around in attempting to define runner's high relates to body temperature.

"Some people think it just might be the elevation in body temperature that is associated with these longer- duration activities, and it may be through the hypothalamus, which is closely linked to temperature regulation mechanisms," says Bryant. "The theory is that the increase in body temperature might in some way indirectly affect mood."

More High, Less Low

While runner's high might be more short-term, it's well-known that regular exercise also offers long-term benefits, on both the mind and the body.

"On average, you tend to see people who are runners and habitual exercisers having better moods, suffering from less depression and less anxiety, and more general feelings of well-being," says Bryant. "For people who are physically active on a regular basis, they have active relaxation -- kind of by moving the body and focusing on the sensation of moving your body and getting into the rhythmic activity and motion, it produces this relaxation response, and that I think contributes significantly to the feelings of psychological well-being."

While marathon running can take its toll on the body, it does offer significant benefits as well.

"Clearly, there are many health benefits of running at this level," says Rick Hall, MS, a registered dietitian and advisory board member of the Arizona Governor's Council on Health, Physical Fitness, and Sports. "A smart marathon runner has put in many hours of training for many weeks or months, before the event, and the health benefits of sustained aerobic exercise are well documented: improved circulation, reduced body fat, lowered blood cholesterol, and better self-esteem."