Accuracy of MyZone calories expenditure?

f1tness4life

Hi,

So after every workout MyZone emails you what your calorie expenditure is. I know you shouldn't eat back all of your calories anyway, but i just wondered if anyone knew how accurate it was?? And if it's not accurate, why isn't it accurate?

Thanks in advance

Azdak

Depending on the activity, Calorie accuracy will range from "sorta, kinda" to "just pick a number at random".
Reasons for inaccuracy:

1. Quality of algorithm. HRMs do not directly measure calories burned. They estimate calories burned using a mathematical formula. There is no standard formula (and companies like Polar keep their algorithms confidential), so your accuracy first depends on the quality of whatever formula the company uses.

2. Even the most accurate algorithm is only applicable during limited exercise situations--I.e. Steady state cardio exercise. If you are not doing steady-state cardio, then what accuracy there is steadily declines. Any type of HIIT, circuit training, kettle bell swings, etc, will be significantly less accurate. Weight training is not accurate at all.

3. Even if you have a good algorithm, and you are doing steady-state exercise, accuracy is affected by the inherent variability of exercise heart rate response in the population. Most HRMs use an age-predicted maximum HR to estimate exercise intensity. However, maybe 1/3 of the population has a true max HR that is 10-30 beats/min higher than their age-predicted number--for them, the HRM will significantly overestimate calorie burn.

nothingtolose90

I know your post is a year and a half old, but I just stumbled across this on the MyZone site and figured I would post it here as well

https://myzone.desk.com/customer/en/portal/articles/1959009-how-does-myzone-calculate-caloric-expenditure-?b_id=8331

How does MYZONE calculate caloric expenditure?

MYZONE calculates the number of calories burnt using an industry standard formula which takes into account a number of personal details including your gender, age, weight and heart rate.

The calorie calculation is based on the most accurate Sports Science white paper in the field

Men: C/min = (-55.0969 + 0.6309 x HR + 0.1988 x weight + 0.2017 x age) / 4.184
Women: C/min = (-20.4022 + 0.4472 x HR - 0.1263 x weight + 0.074 x age) / 4.184

• The calorie calculation is of course based on a number of factors and takes into account gender, age, weight and HR. We have discussed this with various international bodies including the Chief Science Officer at ACE (American College of Exercise) who's feedback was as follows;
• The equation that we are using is the most accurate given the variables that we know about the user (age, weight, gender & HR).
• The equation proves to be very accurate and maintains a linear relationship in the range in which most users exercise (95 bpm – 150 bpm).
• There is inherent variability the with the regression equation to perfect the relationship between HR and o2 uptake at higher HR’s. This is most notable for users who exercise above 150 bpm and have a high max HR. This may cause the equation to report a higher than actual caloric expenditure of up to 10-15% for the time over 150 bpm for this specific user.
• Since our equation uses 75% of the input variables, it is far superior to any calculation that a user would see on a cardiovascular piece of equipment, which uses the inputs of an average human and does not personalize the feedback to the extent that our equation does.
• The actual numbers in the formula are from the most accurate and accredited white paper journal in sports science for this calculation. To explain where they get those numbers from is a thesis from tests done. Here is the white paper if you wanted to have a look: http://www.braydenwm.com/cal_vs_hr_ref_paper.pdf