By Ben Preston Alexandra Stevenson has been holding a tennis racket ever since she can remember. The decision to go pro at 18 took her from the relative comfort of a scholarship offer at UCLA and thrust her into the pressure cooker of competition. It also exposed her body to the kind of beating that mere mortals can only dream about. Having suffered a number of injury-related setbacks over the ensuing years, Stevenson thought her career was through by 2010. But then, something changed. After being carried off a Sydney court with a foot injury in February of last year, she decided to try a new kind of training program called Foundation Roots, a regimen focused on lower back and posterior muscle movement.