Want to boost your testosterone, lads? Go chop some wood

Chopping wood produces more testosterone in men than competitive sports do, claims new research from the University of California.

Anthropologists Ben Trumble and Michael Gurven from the Institute of Social, Behavioural and Economic Research studied the amount of testosterone in the saliva of a group of Tsimane forager-farmers in the Bolivian Amazon. They claim to have made discoveries which change how scientists understand testosterone's role in the human body, namely that it doesn't only exist to increase competition and aggression among other men.

"By focusing so much on the role of testosterone in aggression and competition, we have missed out on the importance of testosterone in a variety of other tasks," lead researcher and post-doctoral fellow, Trumble, tells ABC.

The study, published in the journal Evolution and Human Behaviour, found that one hour of tree chopping caused in a 48 per cent increase in salivary testosterone levels in all men, regardless of age or quality of health. By contrast, testosterone levels only increased by 30.1 per cent while playing a soccer game.

Increases in testosterone improves the muscle’s ability to take in blood sugar from food, which in turn, enhances performance for playing soccer and chopping wood.

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Trumble suggests these spikes in testosterone while chopping wood have important implications because it shows the Tsimane men are physiologically motivated to provide food for their families and themselves.

He also maintains that testosterone plays an important role in fighting off illness and maintaining muscle mass, two things that may have little to do with competition.

“An infection from a pathogen or parasite –– even injuries, burns, or surgery –– all cause an immediate decrease in testosterone,” Trumble tells Science Blog.

Similarly, skipping meals can drop testosterone levels by as much as 10 per cent, he says. And if men fast for a couple of days, they decrease testosterone to devastating levels. This is because they are using testosterone to maintain their muscle mass.

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Trumble believes the Tsimane men have to choose between using calories and testosterone to protect immune function (namely fighting off illness) or growing muscle mass. "There are only so many calories available for the body to use as energy, and so we face a trade-off between investing in survival-related tasks like immune function, or in less critical functions like [maintaining or growing] muscle mass," he explains to ABC.

And finally, the researchers claim to have stumbled upon another interesting finding. While Tsimane men have a relatively low baseline testosterone level –– 33 per cent lower than that of men living in the United States, who are considerably less active –– they appear to maintain their testosterone levels over the course of their lives. Yet men in industrialized countries generally experience decreases in testosterone as they age. "Even late in life, Tsimane men can express the same spikes in testosterone as younger men," Trumble says.