3

I used an elliptical machine at high intensity (not crazy high) for around 20 – 25 minutes, the elliptical machine workout said that I burned 600 calories where as the heart rate monitor said that I burned 330 calories.
I did specify my weight in the elliptical machine but entered a lot more info (age, height, weight, normal heart rate etc..) on the heart rate monitor.
Which one would be more accurate?

Edit
Is it possible that the elliptical machine also takes into account the workout after-burn and that is why it is higher? The heart rate monitor calorie counter keeps going up (faster than normal) even after I finish the workout, so eventually it might end up more or less the same as the elliptical machine calore counter (i.e. when the heart rate returns to normal)?

Viv
  • 316
  • 2
  • 8
  • The time required to return to a resting heart rate varies based on conditioning. Even if this were factored in, I'd guess it would be only accurate for a very small segment of the population. – Christopher Bibbs Aug 10 '11 at 18:20
  • 1
    I think the reason the machine keeps counting is because that makes users happy and whatever makes users happy makes them happy. Either way, after-burn is surely not taken into account – Ivo Flipse Aug 10 '11 at 18:34
  • 1
    Short answer @Vivek - those "calorie counters" on all exercise machines, are just silly. They are worthless. Note that IN A LABORATORY it is extremely difficult / often impossible to measure "calories burned" precisely. They are, quite simply, a silly marketing gimmick - turn off and forget about it. Just watch your heart rate on the heart rate monitor. And watch your waistline shrink! :) – Fattie Aug 10 '11 at 19:50

2 Answers2

2

Heart rate monitors are almost always more accurate than the readings on cardio machines. Even cardio machines that can pick-up your heart rate don't usually have enough information (e.g. resting heart rate) to do the proper calculations.

Christopher Bibbs
  • 1,970
  • 12
  • 10
  • Care to elaborate somewhat on why they can't estimate it correctly? I'd say they all use one generic formula, which simply doesn't hold up for everyone. Even if they enter weight and age, that's still lacking a lot of relevant information. However, that's no guarantee your heart rate monitor will be more right, unless you know how to calibrate it. – Ivo Flipse Aug 10 '11 at 09:32
  • Edited my question to take into account the workout after-burn. – Viv Aug 10 '11 at 17:43
  • @Ivo Good point. I'm thinking about the HRM I've used that linked into a computer and had a resonable set-up routine. – Christopher Bibbs Aug 10 '11 at 18:22
0

A common formula for approximating calorific expenditure is:

Kcal/Min ~= 5 * massKg * VO2 / 1000

Given both devices had the duration of the session and your Weight that leaves the VO2 figure as the source of the discrepancy.

The machine will just have had an assumed constant and as you were not wearing a bluetooth based face mask to capture the actual volume of Oxygen consumed, every minute, your devices will have guestimated a value based on your heart rate in each period e.g.

VO2 = (currentHeartRate / MaxHeartRate) * VO2Max

where:

MaxHeartRate ~= 210 - (0.8 * ageYears)

VO2Max ~= 15.3 * (MaxHeartRate / BasalHeartRate)

BasalHeartRate = Resting Heart Rate

From these formula you can probably work out both the VO2 figure the trainer assumed and the value your phone calculated for you.

arober11
  • 1,185
  • 7
  • 20