What’s behind a runner’s high?

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Elation, clarity and freedom - it's the runner's high. Traditionally put down to the release of endorphins, a recent Canadian study published in the journal Cell Metabolism has found another additional explanation as to why running makes us feel so great: dopamine. Dopamine is a neurotransmitter with a number of functions, the most well-known of which being its roles in motivation, reward reactions and cognitive activity.

Lead author Stephanie Fulton said "We discovered that the rewarding effects of endurance activity are modulated by leptin, a key hormone in metabolism. Leptin inhibits physical activity through dopamine neurons in the brain."

Leptin is a hormone made by fat cells which signals satiety to the body and discourages physical activity. "The more fat there is, the more leptin there is and and the less we feel like eating. Our findings now show that this hormone also plays a vital role in motivation to run, which may be related to searching for food," said Fulton.

The study compared the wheel running activity of normal mice to mice who'd had their STAT3 molecule suppressed, which is typically activated by leptin and helps compound dopamine development.

The results? "Mice that do not have the STAT3 molecule in the dopaminergic neurons run substantially more. Conversely, normal mice are less active because leptin then activates STAT3 in the dopamine neurons, signalling that energy reserves in the body are sufficient and that there is no need to get active and go looking for food," according to first author Maria Fernanda Fernades.

As previous findings have shown a link between low leptin levels in humans and better marathon performance, the study's authors suggest that "low leptin levels increase motivation to exercise and make it easier to get a runner's high."