It's a bummer this didn't work out for the OP, but how to talk to iPod-treadmill-gym girls is a valid question.
My suggestions:
Pull the fire alarm at the gym. Everyone will evacuate except her, since she won't be able to hear the alarm over the iPod. She'll then realize that you and her are all alone in the gym. She will then be overcome with desire. Then sexy time will come.
Sneak up behind her and unplug her treadmill, then catch her as she falls backward. Look at her with your best "WTF just happened?!" face. Being held there in your spindly arms, she'll be overcome with desire. The result? Sexy time. (Warning: In the event she falls forward and slams her head into the treadmill display, then just casually walk away. This could be construed as assult.)
Get a friend of yours to go over and start harassing her. Then go step in. Challenge your friend to kung fu fight for the girl's honor. Proceed to kick the crap out of your friend by utilizing a series of devestating roundhouse kicks (Note: Don't use a good friend for this.). Seeing such a chivalrous display, she will be overcome with desire. Sexy time will be inevitable.
Show her you're culturally sensitive! Stand directly in front of her treadmill and begin studying your Rosetta Stone. Which one? You should customize this for the girl. Asian? Then Chinese. White? Then Russian. Black? Then Jive. Seeing how worldly you are, she will be overcome with desire. At this point, sexy time will be unavoidable.