Male kangaroos purposely flex their biceps to impress females. Rating: Unproven (About this rating?) Context: Although male kangaroos do appear to flex their muscles to show off their impressive ...

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Any gym-going female human knows just how much men like to show off their muscles. But it turns out that it’s not just male humans who think that flexing their biceps at ladies is an effective ...

Beth Skwarecki is Lifehacker’s Senior Health Editor, and holds certifications as a personal trainer and weightlifting coach. She has been writing about health for over 10 years. Curls are the classic ...