Wahoo calorie count

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si_c

Guru
Location
Wirral
That is what I use them for really just as a guide... just completely baffled why the changes...
Looks like they've changed how they estimate calories on the device if you use an HR meter and are tracking intensity.

It may be closer to reality than before in fairness. I weigh close to 100kg and estimate 55kcals per mile for rides.

The only way you can be sure of your calorie burn is to get a power meter. This is what I did as I wanted to know for sure, the calories for my commutes at the time rose by about 40% when compared to the estimate.
 
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stuarttunstall

stuarttunstall

Senior Member
Location
Yorkshire Wolds
This is the reply from Wahoo.. maybe the calculation now is more accurate but if that is the case it must have been way out before.. and I mean bu about 300-400 calories on the ride I do...

Based on your calculation, similar weight then the 14 miles I do at 55 cal/mile is about 770 and I see between 700-900 now..

"Hi Stuart

We recently made 2 changes to the calculation of calories. Historically we have always used heart rate data to calculate calories regardless of whether a power meter has been paired to the head unit, as a result, there were often differences between the Calorie recording and the Kilojules [Kj] recorded. However, now, we will always calculate this based on power data if it is available. The reason for this change is to improve the accuracy of this data point.

Kilojules are a cumulative measure of energy [kilojoules = watts × seconds / 1000] which is calculated from power data. Using this we can make an accurate [to within 5%] calculation on the number of Calories burnt by using the Kj data from a ride. It is widely accepted that when accounting for Gross Metabolic Efficiency [GME], which is a measure of how good our body is at converting food in - into power out, 1Kj is equivalent to 1 Cal. What this means is when viewing your ride data you will now likely see a much close correlation between Calories and Kj.

To explain this a little more see below.

Because most humans are only around 20 - 25% efficient at converting fuel into energy [in this case power on the bike] most people need to consume 4 Calories for 1 Calorie burnt through cycling.

So although in actual fact, 1Kj is only equal to 0.239 Calories. We must include the information relating to human efficiency into the calculations when calculating a total. As a result, we must multiply the pure calorie number burn, which is calculated using this equation [Kj burnt x 0.239], then multiply this value by 4.184 to get our total Calorie burn estimation for a ride.

For more information on this calculation, I would recommend reading the following article from Trainer Road that explains it in more detail.

https://blog.trainerroad.com/calories-and-power/

The Second change we have made relates to how Calories are calculated when no power data is available. In this case, Heart rate data is used. More information on the calculations used in this scenario is found in the link below.

https://support.wahoofitness.com/hc...calories-calculated-in-the-Wahoo-Fitness-App-

This calculation has been edited to produce a more accurate value.

Please let me know if I can help you with any other questions,

All the best,

David"
 

figbat

Slippery scientist
Wait, so they are using kJ and kcal as different measures? kJ to report on the expended energy at the crank and kcal to report energy metabolised by the rider? When in truth they are simply imperial and metric units of the same thing.

Am I missing a cycling thing - is this a normal definition of kJ and kcal, or is this just Strava not understanding the difference between metric and imperial units? They have form here - you can't, for example, have miles and °C together - as far as they are concerned you are either American (miles, °F, lbs) or foreign (km, °C, kg).
 
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stuarttunstall

stuarttunstall

Senior Member
Location
Yorkshire Wolds
Makes no sense to me at all ho it can change so much, I accept that it is a guide anyway but to "make it more accurate" and it adds twice the value then something is not right...

This is Wahoo by the way not Strava :smile:

I'm 56 and imperial all the way, don't do metric lol
 

si_c

Guru
Location
Wirral
Wait, so they are using kJ and kcal as different measures? kJ to report on the expended energy at the crank and kcal to report energy metabolised by the rider? When in truth they are simply imperial and metric units of the same thing.

Am I missing a cycling thing - is this a normal definition of kJ and kcal, or is this just Strava not understanding the difference between metric and imperial units? They have form here - you can't, for example, have miles and °C together - as far as they are concerned you are either American (miles, °F, lbs) or foreign (km, °C, kg).

A calorie is the amount of energy required to raise 1g of water 1°C - however this varies with temperature, but for practical purposes the a calorie can defined as 4.184 Joules. For food and diet the "large" calorie or more precisely the kcal is used - 1000 calories.

The kJ calculated is the amount of work done at the crank, so you could in theory map that directly accross to calories using the aforementioned ratio. Unfortunately because we use calorific values to assess our food consumption we actually have to map the number of kJ of work done into the number of food calories used to do that work - the human body is inefficient (between 20% and 25%) so we need to multiply this back out to get the final number. Depending on the exact level of efficiency assumed different calculators will give different results.

Of course the example above is for situations where the exact power output is known - the case only if you are using a power meter - when using a HR monitor then the power output can be estimated using a number of means all of which will result in slightly different calculations again.
 

Inspector Monkfish

Active Member
This is the reply from Wahoo..

"Hi Stuart

We recently made 2 changes to the calculation of calories. Historically we have always used heart rate data to calculate calories regardless of whether a power meter has been paired to the head unit, as a result, there were often differences between the Calorie recording and the Kilojules [Kj] recorded. However, now, we will always calculate this based on power data if it is available. The reason for this change is to improve the accuracy of this data point.
......

Thanks for the investigation and follow up. As I use a power meter this will explain why I am now seeing a lower calorie burn Vs you and others seeing higher figures
 

Ming the Merciless

There is no mercy
Location
Inside my skull
I don’t have a TV
 
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