Caster Semenya (right) competes during the 2016 Summer Olympics in Rio de Janeiro. Semenya filed a discrimination lawsuit against the International Association of Athletics Federations, challenging a rule that female athletes’ testosterone levels must be below a certain limit. (Credit: CP DC Press/Shutterstock)

New research finds that women with boosted testosterone levels develop more lean muscle mass and can run longer before getting tired.

Though some researchers and activists think t