To shed the 50 pounds she gained while pregnant with twins Max and Emme
, Jennifer Lopez
, who teamed up with trainer Gunnar Peterson
to get in shape for the annual Nautica Malibu triathalon. "Jennifer is naturally predisposed as a runner," says Peterson, who started the former dancer off with short sprints, bike rides and laps in the pool, gradually upping the distance and intensity as her stamina increased and the race neared.