"For years, scientists (most of them women) studying breast movement during sports have struggled for respect. A 2007 report about the work being done in the field of breast biomechanics at the University of Portsmouth was titled, rather defensively, “Bouncing Breasts: A Credible Area of Scientific Research.” …In fact, one of the most telling recent studies…concluded that the most effective style of sports bra, particularly for women who wear a D-cup bra or larger, does not yet exist, at least in stores."

Phys Ed: The Right Kind of Sports Bra - Well Blog - NYTimes.com