You were in first the whole way, but then coming down a hill you fell and everyone passed you. When you finally catch up to them at the finish line of the first section of your run, the transformations begin.
Liz who finished firsts bra disappears and her breasts start to expand from their previous A cup to a full C cup.
Maddi who finished second's bra dissapears as well and she goes from her previous flat self, to a fully developed, huge on her small body, DD cup.
Then Amanda begins to change. You watch in astonishment as she slowly becomes a C cup sports bra which magically puts itself on Liz.
Then you start to feel an undeniable urge to touch Maddi's breasts. But it's strange, it's nothing sexual, you just want to support them up. Then you look down and realize your becoming a DD sports bra for Maddi.
Maddi and Liz decide to make a bet for the second portion of the run, while you and Amanda are sports bras. They bet that...