Philadelphia Magazine’s Jumpstart Challenge 2010

See which one of our four contestants lost the most body fat throughout our eight-week challenge (and scored some super-cool prizes!)

One contestant is working out with her daughter on the weekends, another is slipping into back-of-the-closet clothes. Learn how to avoid the dreaded weight-loss plateau here

 There are only a few weeks left for our four Philly Mag Fitness Challenge contestants to shed any unwanted pounds, and their trainers are mixing things up as much as possible in order to avoid what anyone with a weight-loss goal fears most — the dreaded plateau. “The body tends to hit a plateau in the fourth or fifth week, and all of the contestants have the possibility of seeing that happen,” says Meghan Anderson, who’s training 24-year-old Jessica Aiken and 39-year-old Jim Schindler. “But that’s why right now we’re really pushing them and amping things up.” That means lots of circuit training for Jessica and Jim — weight exercises interspersed with high-intensity cardio, like treadmill sprints or squat jumps — because it’s a great way to up the burn of workouts if you’ve hit a weight loss wall. “Squat jumps are great in between strength moves because they really get the heart rate up,” says Anderson, who says Jessica does up to five sets of 12 each workout. (See how to do one at home below.)

“We don’t have any specific exercises that we do repeatedly because I don’t want the muscles or mind to become bored,” says Holly Waters, who’s training 25-year-old Devon Montgomery Bender. “So she’s swimming and rowing like a champ and we also get her on the treadmill with an incline and lifting weights over her head as she walks. Anything that takes the limbs away from the body causes the heart to work harder, and you’ll burn more calories. Even walking with your arms over your head without weights can help.”

To try a squat jump at home, lower down into squat until knees are at a right ankle. Jump into the air as high as possible, raising arms overhead. Land softly on balls of feet. Repeat 12 times between each strength move.

So who will be our winner? Jim now fits nicely in a used-to-be-snug coat, Devon’s shed nearly 20 pounds, Diedre’s rocking her old dresses, and Jessica’s trimming inches all over. Check out our contestants’ daily diaries below and make sure to root them on with your comments.