No time? No problem. This fit-in-a-flash HIIT workout burns mega-calories in just 30 minutes.

The promise of a workout that builds muscle and burns fat fast may sound like the stuff of late night infomercials, but it’s actually a real fitness movement, backed up by real science. Called High Intensity Interval Training, or H.I.I.T., the workout features a sequence of short bouts of hard effort followed by low intensity recovery periods. The workouts can be done over the span of 15-30 minutes, but there’s a catch: In order to achieve results in such a short amount of time, the intense exercises require your maximum effort. This will hurt—but you’ll be done in way less than an hour, making it the perfect regimen for this harried time of year.

For best results, do this workout once a week and log your results to see improvement. Also, because this is a really intense type of training, you really only want to add H.I.I.T. intervals to your workout a couple of times per week—four times a week at most.

Workout:

(1) Jump rope: Do 100 reps then rest for 45 seconds, repeat 3-4 sets; advanced athletes should do 4-5 sets of 200-250 reps with only 30 seconds of rest. Stay on the balls of your feet and focus on being light on your toes as you jump. Keep your form tight and agile, even as you begin to fatigue.

(2) Plyometric split squats: Begin at the bottom of a lunge position with both knees at 90-degree angles (to avoid injury never go past 90 degrees). With your core engaged and your torso straight, jump up from the lunge position, landing in a lung position with the opposite leg now leading the lunge. Try to make the movement as explosive as possible, and make sure to land softly to protect your knees. Beginners and intermediate athletes should do 3-4 sets of 10-20 reps, with 45 seconds of rest in between sets. Advanced athletes should do 4-5 sets of 30-50 reps with 30 seconds of rest between sets.

(3) Plyometric straight leg deadlift: Stand on your right leg, keeping a slight bend in the knee. Hinge forward with your body by bending at the hip—not at your lower back. Your left leg will swing out behind you to help you balance. Reach down toward the ground, with how close you get to the ground depending on your level of flexibility. Go until you feel a bit of a stretch, but don’t push it. Return to the starting position, and as you reach your original stance, push off the floor with your right leg and land back on it. Do 10 reps on your right leg, then switch to the left and do 10 more. Beginners should perform 3-4 sets like this with 45 seconds of rest between sets, while advanced athletes should aim to complete 4-5 sets with 15 reps per leg and 30 seconds of rest.

(4) Sprint intervals: Do 3-5 sets of 30 seconds running followed by 15 seconds of sprinting, or if you’re a H.I.I.T. master, do 5-10 sets at the 30:15:30 ratio. Run continuously through the sets, with the 30 seconds serving as “active recovery” time. Keep in mind, for this to work, during the 15-second “on” periods you should be running as hard as possible.

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