First, let me make one thing clear, I am writing about this topic because it is a major pet peeve of mine. Consistently I have clients telling me, I burned “x” calories on “y” machine (calorie readings from cardio machines and/or heart rate monitors (HRMs)), isn’t that great?!?!? While I am happy for them, and proud of the hard work they are putting in, I am also annoyed that based on false science the cardio machine companies are tricking people into thinking they are burning more calories than they actually are. Why would this be a pet peeve of yours, you ask? Because when people think they burn more, they believe they can eat more, hence having a detrimental effect on weight loss and waist size.
Now, do not get me wrong, those calorie numbers can be beneficial, but not in the way they are being interpreted. That number comes in handy when you use it as a guide, not gospel, in which you are trying to burn more calories than the last workout in the same period-of-time. For example: Monday you “burn” 300 calories in 20 minutes, and Tuesday you burn 350 calories in the same amount of time. Clearly you worked harder on Tuesday.
Let’s start with something positive about HRMs and cardio equipment. Both are fairly accurate in reporting heart rate, with HRMs being within 5% accuracy of EKG readings. Heart rate can then be used in a formula to calculate calories burned. That was that, now on to the negative.
Cardio machines vary in their caloric expenditure readings, with elliptical being the worst culprit. On average treadmills are off by 13%, stair steppers by 12%, and elliptical by a whopping 42%. The inaccuracy of elliptical machines may be due to leaning on the rails, the fixed plane of motion, or a combination of the two factors. Bikes were the most accurate at 7% as they use Watts, which incorporates power produced, to calculate caloric expenditure. That being said, the more information that one enters: age, weight, etc., the more accurate the reading. Otherwise the machine default is that of a 160-180lb man, and the calories he would exert during your workout. Are you a 160-180lb man??? Also, what these machines do not consider is fitness level, exercise economy, or body fat/lean body mass percentages. A person who is more fit will burn fewer calories as their body is used to exercise, and a person with more muscle mass will burn more calories than someone with more body fat. Instead of relying on the machine or HRM, use these guidelines for CALORIES BURNED BY MINUTE:
- Low intensity: 2-6 calories
- Moderate intensity: 8-12 calories
- High intensity: 12-20 calories
HRMs miscalculated caloric expenditure by 20-93% by various brand! 93% inaccuracy, that’s absurd?! In fact, in a 2-year study of weight loss by those using HRMs compared to those not using HRMs, those not wearing the HRM lost more weight. As I mentioned above, this may be due to eating extra from the belief that one burned more calories than they did. Again, these numbers should be used as a guide to work against, not gospel.
While there may be a level of inaccuracy with HRMs and cardio equipment, they can still be valuable tools in your fitness pursuits when used properly. Working Heart Rate was fairly accurate, and that information can be useful in showing one what intensity level they are working within. That number can also be used in the linked formula to find actual caloric expenditure. And while neither HRMs or cardio machines were accurate in their working calorie burn estimations, that number can be used as a guide to build off and try to beat in each cardio session. Keep working hard, stay positive, and you will see your goals come to light.