Finally, an explanation as to why soccer is the world's most popular sport.

Researchers have determined that playing a game of "football" improves men's testosterone levels.

The U.K.'s Daily Mail reports results of the new study that claims players saw a 30 percent increase in testosterone immediately after a game. In addition, that boost was still at 15 percent even after an hour after they finished a game.

Scientists from the University of Washington Biological Anthropology and Biodemography Lab researched farmers in Bolivia since the men there normally have lower testosterone than men in America. The study focused on farmers from the remote Tsimane tribe. Illnesses such as heart disease and obesity are rare among tribe members who maintain a stable level of testosterone during their lifespans.

"Maintaining high levels of testosterone compromises the immune system, so it makes sense to keep it low in environments where parasites and pathogens are rampant, as they are where the Tsimane live," said Ben Trumble, a co-author of the study, according to Science Daily.

The report indicates that similar testosterone growth has also been discovered in men in America and similar industrialized countries following participation in sports.

Higher testosterone levels lead experts to believe competition-linked bursts of the hormones are a crucial part of the human biology that continues even if it increases risk for sickness or infection.

--Follow Ben Maller on Twitter @BenMaller.

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