Finding time to workout is tricky in any season, but with a crammed holiday schedule, it can seem nearly impossible. Thankfully, high-intensity interval training—the trending fitness philosophy that combines bursts of cardio and strength training—makes the most of small windows. "Scientifically, you burn more fat by including short spurts where you work your absolute hardest," says Ellen Latham, a trainer and founder of Orangetheory Fitness studios. Here, Latham's 20-minute routine designed to torch calories and firm you up all over. All you need is a jump rope. Do the routine three times a week for body-con, dress-worthy results.
WARM-UP Do 20 high-knee marches while pumping your arms, 15 jumping jacks, and 10 standing straight-leg side swings—lifting your leg out to the side while balancing on the other, then quickly switching back and forth.
CARDIO BURST (4 minutes) Jump rope with a skipping style, alternating each foot (rather than hopping on them together). "You'll know your heart rate is at the right intensity when your breathing becomes too hard to say your full name and address without stopping," advises Latham. Aim to keep it at that level for the full four minutes.
BURPEES TO PUSH-UPS (1 minute) Starting in a standing position, bring your hands to the ground, kick your feet out behind you into a plank position, and do a push-up (drop your knees if necessary). Hop your feet back underneath you and spring straight up, jumping as though you were trying to touch the ceiling. Repeat.
SIDE PLANKS (1 minute) On the floor, place your right elbow directly under your shoulder while propped up on your side. Stack feet or stagger them, and elevate your bottom hip to make a straight line from head to toes. Slightly pinch in your shoulder blades (without hunching). Drop your right knee down for support if need be. Hold for 30 seconds, then switch sides and repeat.
CARDIO BURST (5 minutes, 30 seconds) Jump rope, skipping again, getting your heart rate back up. After two minutes, jump with a slight jog, as if you were running in place. At the 10-minute mark, hop with feet together, like traditional jump rope, for 90 seconds. "For your knee health, land on the balls of your feet, not flat-footed," notes Latham. Be sure you're breathing hard the whole time.
SQUATS TO LUNGES (1 minute) Stand with feet shoulder-width apart, and with your weight in your heels and your hands out in front of you, sit back to a squat—like you're sitting into a chair with your behind stopping at seat level. Stand and lunge your right foot straight forward, keeping the knee above your ankle as you lower your left knee until it hovers above the floor. Step back to standing, then lunge with the left leg forward. Stand, return to squat position, and repeat.
FRONT PLANK (90 seconds) Facing down on the floor, prop yourself onto your elbows and toes with your knees lifted. Focus on pinching your shoulder blades and pulling your belly button away from the front waistband of your pants. Latham's tip: "The ab muscles that kick in when you cough—those are the muscles you want to be engaging." Hold for 90 seconds.
CARDIO BURST (4 minutes) Jump rope with a running step for three minutes, then jump with feet together for one minute.
BICYCLE (1 minute) Lying on your back, bring your right knee up to your chest and stretch your left leg straight out, lowering it as close to the floor as you can without arching your lower back. Then, with your hands behind your head, bring your left armpit toward your right knee and your right elbow back. Alternate sides continuously, focusing on bringing the back elbow far behind you.
BACK EXTENSIONS (1 minute) Face-down, tuck your toes under, and place the backs of your hands under your forehead for support, elbows out to the sides. Using your back muscles, lift your chest as high as you can. Lower and repeat.
FINISH Gently stretch out your back, hips, chest, and the front and backs of your thighs.
(December 2015/January 2016 issue of Harpers BAZAAR)