In pictures: see your favourite stars working out
However, Madonna's spokesperson, Liz Rosenberg, has denied that the 'Celebration' singer will take part on the 2010 Marathon des Sables in Africa. Rosenberg told Contactmusic.com, "It's not true".
In pictures: The material girl
The marathon takes six days or seven, depending on fitness level to complete. Competitors can face temperatures of up to 50°C during the day, while they run over the sand dunes that make up roughly 20 percent of the course.
Your say: Would you ever compete in "the world's toughest footrace"? Do you think Madonna could do it? Do you think Madonna's rep could be denying the star's entrance to reduce publicity?