04/19/2010 at 01:00 AM EDT
THE WORKOUT Post-baby the L.A.-based trainer started Hudson off with a simple five-day, 25-minute circuit-training plan that involves cardio, shoulder presses, lunges and crunches. Then Hudson added a 25-minute jog to her regimen. "She used to hate running," Pasternak says, "then the last time I was visiting, she took off!"
THE RESULTS "She's really happy about her abs," says Pasternak. "And our goal was to bounce quarters off her butt!"