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Heart Rate Monitors may be Sabotaging Your Results

Oct 23, 2020

If you know me you know I am a huge proponent of utilizing a heart rate monitor when performing energy systems training, ie cardio. It creates accountability and a customized, effective workout. But, that monitor may just be messing up your efforts to burn fat.

I just finished up my conditioning workout. My calf hasn’t quite healed enough to perform speed workouts so I did 12 300-yard shuttles. A 300-yard shuttle is running back and forth at a distance of 25 yards 6 times. Yea it is hard but I love the challenge. Shuttle runs allow me to run; get in some conditioning while protecting my calf.

Monitor on completely focused on my performance and heart rate response, I began my workout. About halfway through my workout, I hear the app say “you are burning fat”. I typically don’t pay any attention to what the app says. I am focused on my heart rate and performance. Then it said it again, “you are burning fat”. It hit me like a brick upside the head! I almost stopped running in my tracks.

“You are burning fat”, what the hell! Of course, I am burning fat. The body is always burning fat, carbohydrates, and proteins. What changes is the percentage of fat s, carbohydrates, and proteins utilized to fuel the activity. For example, the lower the intensity of the activity the higher percentage of fat is being utilized. As the intensity increases the more carbohydrates are utilized. The length of the exercise session determines protein utilization.

Here is an example. If you were to exercise for 30 minutes at 50% of your VO2 max (low intensity) you would burn a total of 250 calories. Because of the low intensity, 50% of the 250 total calories burned, would come from fat, or a total of 120 fat calories burned.

Now if you exercise the same amount of time, 30 minutes but picked up the intensity to 70% of your VO2 max you would burn a total of 330 calories or 50 more total calories. Because the intensity is higher only 40% of those calories would come from fat. Here is the thing 40% of 300 total calories are 132 fat calories, 12 fat calories more. So despite utilizing a lower percentage of fat calories for the exercise session you burn more total calories and more fat calories.

This is what has been known as the “Fat Bruning Zone”. It is extremely misleading and has been around for decades. The body burns fat most efficiently while we are sleeping. Now don't start going on the sleep diet.

If fat loss is your goal, interval training is the most effective way to burn fat. Utilizing a heart rate monitor to facilitate a fat-burning session is the gold standard.

Her is how you do it. First, determine your heart rate ranges. To do that 220- minus your age. This is your estimated maximum heart rate. Multiply your estimated maximum heart rate by .7  and .9. Take me for example. I am 61 years old. 220-61=159 beats per minute (bpm). 159bpm is my estimated maximum heart rate. 159 x .7 = 111bpm and 159 x .9 = 143 bpm.

Now that you have those numbers you are ready to workout. Warm-up for 5 to 10 minutes getting to the low number of your range. Now that you are done warming-up start increasing your intensity to get your heart rate up to your upper range. Once you hit your upper range rest until you hit your low number and repeat.

Try to get your heart rate from the lower number to the upper number in less than two minutes. Don’t be concerned with how long it takes you to get to the lower number. That time will shorten as you get into better shape. This interval training method will not only help you burn more total calories and fat during the workout but your post-work caloric expenditure will be more.

There you have it. Why a heart rate monitor may be sabotaging your results. A heart rate monitor is an essential tool for cardiovascular training. When utilized correctly it will get you better results. Don’t be fooled by the “fat-burning zone”. Interval training is the most effective way to burn fat and improve aerobic capacity.

Feel free to contact me if you have any questions. I would be happy to help you improve your results.


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