We have a theory as to why Rihanna is so comfortable in a bikini (or even naked, for that matter). She grew up in Barbados, and when you spend your formative years essentially in a tropical paradise, you probably get pretty darn comfortable baring your goodies on the beach. 

Even though RiRi was born with a stunning body, she knows that she's got to keep it right and keep it tight! On the road, the pop star squeezes in 25-minute workouts three times a week, but when she's home (which is like never), she works out five days a week.

Though if she keeps up her hard partying ways, that can really do a number on a toned and taut physique. But work hard and play hard is definitely Rihanna's motto!

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