Looking to blast calories? Get ready — it\’s going to be intense.  \”It’s got to be high intensity, whatever the workout is, if you’re going to torch calories — not just burn them,” says Bret Emery, a behavioral psychologist and weight loss specialist based in Weston, Fla. \”Heart rate is key. That’s the speedometer of the body. If we speed the body up, it will burn more calories, just as a car will burn more fuel if it speeds up.”

Also, you need to mix up your workouts so they stay challenging. This will help keep your heart rate up, and force your body to burn more calories, Weston says

The following workouts will zap calories, but they’ll also push your body way past your comfort zone. So check with your doctor before taking on the challenge.
 If you\’re not active now, remember that it is better to ease into exercise in order to help prevent injury.

Interval training is all about challenge and recovery — over and over — for a cardio blast.  This particular workout uses a treadmill. If you\’re already fit, you can add dumbbells for an extra challenge.

1. Warm Up: On the treadmill, with the incline set at a challenging angle, power walk at a speed of 3-3.5 for 7 minutes. Keep your elbows up above your heart. Stop, get off the treadmill, and stretch.

2. Sprint: Drop the incline to 0, increase the treadmill speed, and sprint hard for 30 seconds. Aim for 90% of your maximum heart rate. To recover, bring your speed down to 3.0 and walk for one minute.

3. Squats: Get off the treadmill and squat, with your bottom out to the rear and your legs slightly apart. Then jump from the squatting position into the air, landing in the same squat position as before. Do this for one set of 15 or 20, working your quadriceps. If you’re already in good shape, hold dumbbells by your sides.

4. Overhead Presses: Do 15 or 20 overhead presses with the weights, pushing them straight up and directly over your shoulders.

5. Sprint: Get back on the treadmill and sprint for 30 seconds (no incline). The goal is to be at 80% of your maximum heart rate. To recover, decrease your speed to 3.0 and walk for one minute.

6. Tricep Extensions: Using dumbbells, do one set of 15 or 20 overhead tricep extensions. Your elbows should point toward the ceiling, with the weights behind your head. Lift the weights directly above your head and back down again.

7. Pushups. Do one set of 15 push-ups, with your elbows at a 90-degree angle from the body. Modification: Do the push-ups with your knees on the ground, but do 25 instead of 15.

8. Sprint: Back to the treadmill. Sprint for 1 minute, aiming for 70% of your maximum heart rate. To recover, jog for 90 seconds.

9. Jumping Jacks. Do one set of 15 or 20 jumping jacks. If you\’re strong enough, add two 10- or 15-pound dumbbells — lift up the weights when you jump out, in an overhead press position, pulling them back down to shoulder height as your legs go back together.

10. Finale: Incline your treadmill to an angle that really challenges you — but don\’t hang onto the treadmill\’s rails. Walk at a 2.0-3.5 speed for 30 seconds, aiming for 60% of your maximum heart rate. To recover, bring the treadmill down to a 1.0 incline and drop your speed to 1.9 or 2.0 for a 1-minute walk. Finish by stretching.

Exactly how many calories you burn depends on your weight and how intensely you do the exercise. Check out this website for some caloric burning guidelines based on certain activities: