Begin with three weight-training sessions each week, recommends Joe Dowdell, founder and co-owner of the New York City gym Peak Performance. For the greatest calorie burn, aim for total-body workouts that target your arms, abs, legs, and back, and go for moves that will zap several different muscle groups at a time—for example, squats, which call on muscles in both the front and back of your legs, as opposed to leg extensions, which isolate the quads.
Complete the exercises in each workout as Straight Sets. For example, you'll do one set of leg presses, rest for 30 seconds, do a second set, rest, do the third set. Then, move on to the next exercise. You'll complete all movements in both workouts this way. Complete 12 reps of all movements for 3 sets each, and rest for 30 seconds in between each set. Choose a weight load where the last two reps of every set are extra hard, where you wouldn't be able to do a 13th rep. You may find that you increase the weight load for each set while keeping the 12 reps for all three sets.