"Hey this really random but if I didn't come over and inappropriately hit on you in the middle of your workout I'd probably kick myself later." Then introduce yourself, qualify her, and then go straight for the number..."well I gotta get back to my workout but lets exchange numbers and if you seem really cool over the phone then maybe we'll hang out".
Keep it very short, under 2 min tops. You can tweak it for other daytime approaches as well.
PM to sarge in OC/LA/LV/SD