Comparison of Heart Rate Monitors to Caloric Burn on Cardio Machines.

I recently bought a heart rate monitor. I do a lot of cycling and thought it would be a good training tool. I love it! But it brought something to my attention that I find a bit confusing. First, a little info for those of you who don’t have heart rate monitors… in addition to telling you what your heart rate is and if you are in your training zone, it also tells you how many calories you have burned in your workout sessions. You have to enter some data (i.e.  your weight, age, height, etc.) into the watch so it is individualized to you.

So here is my question…  I noticed a huge discrepancy in what the cardio machines at the gym say as compared to what the heart rate monitor says regarding caloric burn. For example, I ran 4 miles on the treadmill. After plugging in my weight, the treadmill said I burned off 400 calories, yet my heart rate monitor said I only burned 250. This is 40% lower! I tried the stairmaster (the more difficult one with rotating stairs) and found the same thing – my heart rate monitor said I burned about 30-40% fewer calories than what my heart rate monitor said. I found this very confusing (and annoying!) so I decided to turn to two fitness experts –  Sal Salvatore Fichera, MS, Exercise Physiologist and author of Stop Aging, Start Training and Julia Derek, fitness instructor in NYC.

Martha: So why the huge difference between my heart rate monitor and what the cardio machines at the gym said regarding caloric burn?
 
Sal: Good question. Cardio machines provide merely estimates. The more highly accurate guage is the HR monitor, which is nearly as accurate as an EKG (electrocardiogram).
 
Whereas cardio machines provide estimates based on averages (derived merely from total body weight, and not body fat composition), the HR monitors actually measure the electricity generated by the heart in real time.  

Julia Derek: Julia referred me to the article she wrote on accuracy of calorie counters on cardio machines that I recently posted on CGB. In addition to the info in the article, she also agreed that the heart rate monitors are more accurate.

I would invite all CGB readers who have heart rate monitors to test this out. Compare your monitor reading to the reading on the cardio machine at your gym and share the results.

So bottom line, you may not be burning as many calories as you think you are when you exercise – so think twice before grabbing that extra cookie or glass of wine!