It’s not much of a stretch to say that nobody knows how to build power, speed, strength, and flexibility better than Jillian Michaels. This comprehensive workout, which she created for Health, trains the muscles in a way that will bust through even the most persistent plateau. Do it four times a week, paired with 20 minutes of high-intensity interval training, and watch your body be transformed. Go back to the full workout

Are you sitting down? Perfect. Please take a moment to check in with your body. Is your rear kind of numb? Do the backs of your thighs feel smushed? Is your lower back all crunched? This is your body crying out for help! Really.A wave of new research indicates that sitting all day is actively damaging your health. By forcing a body designed for movement to hold a crushingly immobile position, sitting strains muscles, slows your metabolism, increases your risk of heart disease, and even shortens your life span. “Sitting is a health hazard on the order of smoking,” says Marc Hamilton, PhD, a microbiologist at the Pennington Biomedical Research Center. I was once like you: I sat 10 to 11 hours a day. And then, in 2008, I was researching an article about newfangled chairs and learned that few of the designers actually sat on chairs because of the ill effects on their health. Tired of that glommed-up, dull feeling I got at my desk, I shoved my chair to the side and tried a standing desk. Over the next six months, I slowly rid my home of chairs. I couldn’t believe how my body responded. My back pain disappeared, along with my poor posture. And 15 pounds nearly fell off my frame. Need more incentives? Here’s why over-sitting must—and can—be stopped. Sitting makes you fatWhen you park your butt in a chair, your metabolism comes to a screeching halt. It’s all because of an enzyme called lipoprotein lipase, which resides in the blood vessels of your muscles. “Lipoprotein lipase captures fat in the blood and incinerates it,” says Hamilton. When you’re standing, the postural muscles that support your weight, mostly in your legs, release the enzyme, which goes to work burning fat. But when you’re sitting still, and not shifting every 30 to 90 seconds as the body does naturally, “the fat stays in the arteries, and can be stored in adipose tissue—also known as body fat,” Hamilton explains.A typical day of sitting lowers lipoprotein lipase activity by 90 to 95% (in animals), which is why when Hamilton takes blood samples of his human subjects while they’re sitting and eating, the plasma—ideally clear—is white and chunky, filled with fat, the sign of a sluggish metabolism. Worse yet, experts say that 60 to 90 minutes of daily exercise may not counteract the effects of sitting all day. In fact, Hamilton says, the biochemical reactions slowed by sitting are completely different from the ones that are activated by your daily workout. The biggest difference between thin and fat people is not how much they eat or exercise, but how much they sit, according to James Levine, MD, an obesity researcher at the Mayo Clinic.In a now famed 2005 study, Dr. Levine placed mildly obese and lean participants with similar, fairly healthy diets in sensored “magic” underwear that recorded their body position every half second. The thin people spent a whopping 120 fewer minutes every day sitting, and the overweight people would have burned an average of 350 more calories if they’d engaged in as many non-exercise-related activities (i…

Protruding stomachs and saggy butts will be a thing of the past, thanks to this power workout. In this video, Health contributor Tracy Anderson shows you how to get maximum fitness impact with minimal time spent at the gym. Do the sequence six times a week for results you’ll love.