“The best way to get great legs fast is to lunge for four weeks,” says Bobby Strom, the Los Angeles-based trainer responsible for getting Britney Spears and Shakira in top shape for big events and music videos. “Lunges recruit so many leg muscles that you will see results almost immediately. They also burn more calories than machines do.”

Strom suggests doing a variety of different lunges and split squats (a stationary lunge) using the morning- after muscle soreness as an intensity gauge. “Don’t overdo it if you’re a beginner,” says Strom. “You should be a little sore the next day, but nothing too intense. If you don’t feel anything, bring it up a notch.” Strom recommends mixing forward, reverse, side and walking lunges, but also suggests mixing in equipment for an added challenge in your workout. “I like the bicycle or the elliptical machine for toning the lower body,” says Strom. “Your feet don’t leave the pedals so you are constantly pushing against resistance.”

TRY Split squats off a step to condition the entire lower body.
•Start with your right foot on a step and your left foot on the floor. Feet should be shoulder-width apart.
•Hold a five-pound weight in each hand and keep hands at your sides throughout.
•Keeping your torso tall, slowly bend your knees until your left knee hovers just above the floor. Your right knee should be over your right foot.
•Hold for two seconds at the bottom, then return to starting position.
•Do a minimum of 15 to 20 repetitions on each side. Switch to a different lunge, then return to the step and repeat. “This is a great move because the step gives you more range of motion,” says Strom.

TRY Swiss ball extensions to tighten the hamstrings and glutes.
•Lie on your back on a mat with legs lengthened and heels resting on a Swiss ball, away from your body.
•Pull the ball in by bending knees, until the ball is almost touching your butt (which is lifted off the floor).
•Hold for two seconds, then slowly return to starting position. Try to keep ball from wiggling and don’t let your butt drop.
•Do up to 20 repetitions.