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If you've been doing cardiovascular training to burn fat, you may have heard various theories regarding the best fat-burning techniques, such as doing cardio at low intensity instead of at high intensity or doing cardio on an empty stomach.

Different fitness professionals have different beliefs, and all the conflicting information out there can lead to misconceptions. Thus, I will attempt to provide some solutions for common mistakes and presumptions about cardio and fat burning.

While none of these theories are set in stone, you will come away with a clearer understanding of how different types of cardiovascular training affect fat burning.

1. Thinking long cardio workouts at low intensity are best

Since your heart rate is not high enough, your body doesn't really get a workout from it.

Solution: Slow/fast workouts (interval training), where you sprint for one minute and then walk for two are best for burning fat. Simply put, a higher heart rate burns more calories. For example, you burn 100 calories in 20 minutes of low-intensity work compared to 160 calories in 10 minutes of high intensity, and you also burn more total fat in less time during a high-intensity workout.

Like anaerobic weight training (training intensity where you are burning fuel without oxygen), combining high-intensity sprints (anaerobic) for 1 minute with walking (aerobic training intensity where you are burning fuel with oxygen) for 2 minutes also boosts your metabolism long after the workout, so you're still burning fat and calories hours after you've left the gym.

2. Not entering your proper weight/height into machines

The machine won't be calibrated with your information, and won't offer personalized results.

Solution: Your actual weight should be taken first thing in the morning, before you have consumed any foods or beverages to tip the scale. Enter that weight — and your height if possible — on the machine and you should be set. If the machine says you burned a total of 150 calories, but you weigh 250 pounds and the machine is calibrated to 180 pounds, this number is likely inaccurate.

Workouts that are too short or are preceded by too many calories can be useless...

3. Thinking a quick cardio workout burns fat cells

If your goal is to burn fat, keep in mind that you only start burning fat cells after approximately 20 minutes of a cardio workout.

Solution: After warming up at low intensity on a treadmill, stationary bike, StairMaster, or stepper for 2 minutes, up the speed to moderate intensity for 10 minutes, then do 2 minutes at lower intensity, then 5 minutes at high intensity, then close with 5 minutes of moderate intensity, and 2 minutes of low intensity as a cool down. Total cardio workout time: 26 minutes.

The website www.fitstep.com offers these simple guidelines: If you are trying to lose fat, you need to do more cardio than if you are trying to gain weight. For fat loss, 20 to 40 minutes of cardio 3 to 5 times per week is plenty. Start conservatively if you are just beginning training (e.g. 3 times weekly at 20 minutes per session.)

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4. Having an energy bar/drink before a cardio workout

By doing so, you only end up burning the calories you just had before hitting your existing fat cells, which is counterproductive if you're trying to lose weight. Remember that energy bars and drinks were designed with endurance athletes in mind, therefore may have hidden sugars and fat which give them a high calorie content.

Solution: Instead, have a low-calorie snack about an hour before the workout (allowing enough time for digestion), such as an apple and a half-cup of low-fat yogurt or cottage cheese. You won't sacrifice energy for the workout, and those minimal calories from the pre-workout snack will be burned quickly during a 20- to 30-minute, moderate- to high-intensity cardio session.

5. Doing cardio training on an empty stomach

People have the misconception that by doing so, you automatically start burning fatty tissue.

Solution: Cited in the book The Men's Health Guide to Peak Conditioning (Rodale Press, 1997), Ellen Coleman, nutrition consultant with The Sport Clinic in Riverside, Calif., has this to say about fasting before a workout: "You don't have to starve yourself, but it's wise to avoid eating 45 minutes to an hour before exercising. Even carbohydrates take at least an hour to digest. Fats take even longer: two to four hours. When your body diverts energy to digestion, it's robbing muscles of power and making your workout less effective."

The bottom-line? Don't starve yourself before a workout and, of equal importance, make sure you are properly hydrated. Training on an empty stomach or with minimal fluids is akin to a car trying to get from point A to point B with no gas. You won't get very far into your training without any "fuel in your tank" after fasting for 5 hours or more; especially if you want to burn fat with a 20-minute high-intensity workout.

Don't make the same mistakes professionals and beginners alike have made...

6. Increasing your body temperature

The false belief is that you increase your metabolism, sweat more and burn more calories. For years, wrestlers ran around in sweat suits in overheated conditions to shed pounds before a match in order to "make weight" (fit into their weight category.) Well, the lost pounds were mostly water weight and they were dehydrating themselves — the wrong way to drop pounds and outright dangerous.

Solution: The safest and effective training method involves wearing loose-fitting clothing (shorts, T-shirt and sneakers) in comfortable temperatures (ideally 68 to 72F) and doing high-intensity cardio for at least 20 minutes. You'll perspire and efficiently burn both calories and fat, and your metabolism will increase as mentioned above, allowing you to continue burning fat and calories well after the workout.

7. Thinking cardio training compensates for bad habits

Eating junk food, binge eating and not getting enough sleep are only a few of the bad habits some overlook when performing cardio training.

Solution: Balanced nutrition, adequate sleep, and regular exercise — that includes both anaerobic and aerobic components — are fundamental for maintaining weight and preventing body fat from accumulating.

Here are some other key points:

— As mentioned above, if you are trying to lose fat, you need to do more cardio than if you are trying to gain weight. For fat loss, 3 to 5 weekly cardio sessions of 20 to 40 minutes each is plenty.

— If you want to gain weight, say for a particular sport, you will find that goal is easily achieved if you don't do much cardio, but stick to weight training 2 or 3 times weekly. You will still maintain health benefits without much effect on your weight gain if you do light cardio (low-intensity activities such as walking or light jogging) twice weekly for 20 minutes.

Keep in mind that the quality of calories (from ample protein, complex carbohydrates and beneficial fats) and the quantity of calories consumed, as well as the amount and type of exercise or physical activity (anaerobic vs. aerobic) all affect your physique. And researchers have found that sleep deprivation actually increases fat storage because it minimizes fat burning.

So, if you're not consistently getting 7 or 8 hours of sleep a night, you'll have a harder time burning fat. Plus, getting regular sleep boosts your recovery between workouts and, along with balanced nutrition, supplies the energy to train.