That shirt is the perfect length...it teases you with a glimpse of her awesome booty while not making it too much. Sometimes, subtlety is sexier than in-your-face. Sometimes. :)
She's also wearing these sexy, vintage style brown leather boots. I mean, what could better compliment a great booty shot video of her riding a workout bike than mixing in some boots. BootsNBooty! She rides while standing up and sitting down as her boots and wheel go round and round.