"I put boxing gloves on her and I'll make her cartwheel to the left side, do a (boxing) combination, and then cartwheel to the right. Afterward, I make her climb a fence. It's about 10 feet high, and I make her climb four steps up, and four steps down eight times... and then we play tennis." Britney Spears' trainer Tony Martinez on the pop star's pre-Las Vegas residency work-out.