In the Coed magazine, they did a poll for sexiest female athletes of 2007. There is a list of sexy female athletes including LPGA, WNBA, figure skating, billiards, surfing, drag racing, mountain biking, triathlete, tennis, track and field, soccer players and so on.
Here are some pictures of them.
Amy Acuff (Track and Field)
Anna Kournikova (Tennis)
Milene Domingues (Soccer)
Sophie Sandolo (LPGA)
They all have really sexy body as good as most famous actresses. They are not only just athletes, but also stars. Usually, women have a tendency what they want to show and appeal their beauty and sexualities. I think it's really natural like men's tendency of showing their muscle.
I do agree with you that guys are portrayed to have big muscles and women are portrayed to be sexy and fit but these are social norms that are constructed from stereotypes. I think that the women in these ads are portrayed in an overly sexual manner and it is a little degrading to them. If these were male athletes they would not be displayed in anywhere close to the sexual manner as these female athletes.