THE WORKOUT: Mari Winsor “Flat Abs Pilates”

WHAT TO EXPECT: There’s a reason Miley Cyrus is so fond of baring her midriff — the pop star has some of the best abs in the business. That’s Mari Winsor’s handiwork. The Los Angeles–based Pilates guru is known for crafting muscles that look long and lean but never bulky. Her popular two-part abs Pilates video on Gaiam TV features 17 ab-targeting moves to strengthen the core, slim the waist and flatten the midsection.
WHAT YOU’LL NEED: A mat or yoga mat.
COST: $1 for first month subscription to Gaiam TV and $10 per month thereafter.
DURATION: 20 minutes each
winsorfit.com

THE WORKOUT: AKT InMotion “Upper Body Chair Workout”

WHAT TO EXPECT: In addition to three studios in New York and New Canaan, Connecticut, personal fitness trainer Anna Keiser — whose impressive client roster includes Shakira, Kelly Ripa and Sarah Jessica Parker — has produced a robust library of virtual workouts available to stream on her website. The newest, “Upper Body Chair Workout,” is 11 minutes and 30 seconds of nonstop, results-driven arm work that targets virtually every muscle between the wrist and the neck. Even Keiser breaks a sweat.
WHAT YOU’LL NEED: Two three-pound weights, a chair.
COST: $8 for individual video or $30 for bundle of four.
DURATION: 11 minutes and 30 seconds
aktinmotion.com

THE WORKOUT: Body By Simone “HTB”

WHAT TO EXPECT: HTB, or “Hips, Thighs and Buns,” is one of the most popular classes at Body by Simone, a New York– and L.A.-based studio known for intense dance-cardio workouts that have attracted everyone from Anne Hathaway to Naomi Watts. At 41 minutes, the online version is shorter than the hour-long studio class, but that doesn’t mean you won’t feel the burn. Glutes and inner thighs get special attention with repetitive sequences designed to exhaust the muscle groups. “You will see results within two weeks if you follow the exercises correctly and devote the time to do it,” says founder Simone De La Rue. “I recommend at least three to five sessions per week.”
WHAT YOU’LL NEED: A yoga mat and Pilates ball.
COST: $10 grants users a one-month unlimited subscription to all the streaming videos on BBS TV.
DURATION: 41 minutes
bodybysimone.com

THE WORKOUT: Ballet Beautiful “Hip & Thigh Blast”

WHAT TO EXPECT: Ballet Beautiful founder Mary Helen Bowers (a former New York City Ballet dancer) regularly updates her website with new ballet-inspired exercise videos. Particularly popular come shorts season, “Hip & Thigh Blast” is a fast-paced workout that focuses on sculpting and toning. Designed to maximize results, it targets the outer thigh muscles to create the illusion in legs, tone and lift the glutes and strengthen the core.
WHAT YOU’LL NEED: A yoga mat.
COST: $10 for the class or $40 for a monthly subscription.
DURATION: 15 minutes
balletbeautiful.com

THE WORKOUT: Physique 57 “Back Body”

WHAT TO EXPECT: Based in New York (with studios in L.A., the Hamptons and Dubai), Physique 57 combines barre-based exercises with cardio and strength-training to deliver long, taut muscles and enhanced posture. “Back Body,” the latest in its series of online videos, zeros in on the posterior, tightening triceps, sculpting the seat and straightening the back. Instructor Neil Totton leads the sequence of exercises (many of which you’ll recognize from the Physique 57 signature class), while two co-instructors demonstrate alternative basic and advanced variations, respectively. Expect plenty of squats, leg lifts and back bends.
WHAT YOU’LL NEED : No props are necessary.
COST: $5 
for individual video or $57 for an unlimited monthly subscription.
DURATION: 30 minutes
physique57.com