And the January 5, 1995 issue of the journal Physiology and Behavior reports that exercise decreases tension and boosts self-esteem.

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The study does not, however, prove that the signals from sweat that the participants' brains responded to are "pheromones, " chemicals found in animals that communicate information and influence responses in behavior and physiology.

CNN: Sweat may give off stress signals, study says

In 135 flights, as the five space shuttles collectively circled the Earth more than 20, 000 times, we learned about the physiology of humans in space and about the behavior of substances in near-weightless conditions.

CNN: Space is still the new frontier