(pr-inside.com) - Rihanna is rapidly rivalling World's Sexiest Woman MEGAN FOX - polls have awarded the R& B beauty the sexiest celebrity legs, hair and tummy.The 22-year-old was handed the latest accolade after she bared her toned belly in a bikini while on holiday with beau Chris Brown.Her tight abs earned her the top spot in a poll conducted by the makers of digestive aid supplement AntiBloat.Second on the list was slender actress Keira Knightley, renowned for wearing midriff-flashing costumes in movies such as Bend It Like Beckham and King Arthur.In third place was Dame Helen Mirren, who wowed onlookers last month (Jul08) with her chiselled midsection as she stepped out in a bikini while on holiday in Italy.Sienna Miller and British model/actress Elizabeth Hurley shared fourth position to round out the top five.