How it works: Follow the calendar, doing each strength or cardio workout on the day indicated. If you have time, add a warm-up and cool-down to the beginning and end of your workout. (Don’t forget to take rest days—your body needs them!)

Strength training workouts: These strength workouts are short (only four exercises each) but intense. By alternating upper- and lower-body moves (in a little thing called supersets), you’ll keep your heart rate elevated and maximize calorie burn while working every muscle in your body. For each workout: Do 12 to 15 reps of the first two exercises back-to-back, then rest for 60 to 90 seconds; repeat for two to three sets. Repeat with the second two exercises. Remember to use a weight that is challenging enough to fatigue your muscles by the end of the set. (Don’t skip strength days; you’ll score all these benefits from lifting weights.)

Cardio workouts: Cardio is broken up into two parts: Steady-state cardio and intervals. On the weekends, do any longer, moderately paced workout (walking, swimming, cycling, etc.) to stay active and improve endurance. During the week, you’ll take on interval workouts to burn calories (thanks, HIIT!). Do them twice a week. While you could use any cardio equipment (rower, bike, elliptical), below you’ll find all four weeks’ worth of interval running workouts you can do on the treadmill. You’ll use your Rate of Perceived Exertion (RPE), or how difficult the exercise feels on a scale of one to 10 (10 being the hardest). If the workout feels too easy, try adding the suggested challenge.