The Secret to J.Lo's Incredible Abs, According to Her Trainer

Jenny from the block has her abs on lock. And there isn’t a crop top or cutout dress that doesn’t know it.

One key to the 48-year-old entertainer’s chiseled middle: side-plank oblique crunches, says her trainer David Kirsch. "It’s perfect for when you need to focus on shaping and toning not only the obliques but the entire core," he says.

Start in side plank, with legs extended and feet and hips stacked; rest left forearm on floor under shoulder. Place right hand lightly behind head (A). Rotating torso, bring right elbow in toward belly (B); return to start. Do 15 reps per side 3 times a week to start seeing toned abs in 2 weeks.