zacster

I've done a few rides this week and was paying attention to the calories on my Wahoo and in general as I try to lose the 10 pounds I put back on after I lost 30. I attribute the original weight loss entirely to cycling, and I have RWGPS stats during that time but before I had a PM. I did about 2 hours of riding on Monday, and the Bolt said I burned 1476 calories during that ride but when it uploaded to RWGPS it showed only half that. RWGPS uses HR data to estimate calories, but the Bolt is using actual power data. I've always used 500cal/hr as a rough estimate myself for my moderate to hard cycling. One is below the other is above.

I'm fully connected with both power and HR, so which should I believe?

John_V 

I don't have a power meter but I do notice that I, more often than none, get varying results in calories burned across different sites. I upload to Strava, RWGPS and Endomondo and usually get three different results for the same ride. I always go with what my Bolt and Tickr record.

ksryder

Power meter.

It's still an estimate, but it's an estimate based on the actual amount of power generated. Efficiency loss differences between calories burned and calories generated are pretty minimal and also pretty standard across a wide range of fitness levels, so the PM is going about as close as you can get outside of a lab.

zacster

And here's what make it even more puzzling to me now. I rode my commuter bike today and took the Bolt with me as I usually do, wore an HR monitor, but didn't have the PM pedals. This time RWGPS completely overestimated my calories IMO, reporting about 1500 calories for what I consider an easy ride. On the ride I did with the power meter a few weeks ago at the start of the thread I was pedaling hard and getting a real workout, and RWGPS reported half the calories for the same bike time. Yea, it all nets out, but that's not my point. Why is it so inconsistent?

gregf83 

Because there are too many unknown variables (wind, drafting, clothes you are wearing, position on the bike etc) for an on-line calculator to provide a reasonable estimate of calories expended.

DrIsotope

A calorie number based on heart rate might as well be randomly generated. Everything affects heart rate. Power is power.

njkayaker

Is RWGPS estimating the calories or just reporting what the head unit days the calories are?

Seattle Forrest

How many heart beats are there in a calorie?

DrIsotope

Based on an online calculator's guesstimation of my BMR, combined with my resting heart rate... about 44 beats per calorie. Like... I guess when I'm asleep.

caloso

Power meter.

TimothyH

https://www.trainingpeaks.com/blog/h...lorie-reading/


-Tim-

JohnJ80

^this.

I was shocked when I was looking at the calorie burned numbers from 3 different bike computers a few years ago. They varied by almost 100% method to method/computer to computer. If you want reasonably accurate caloric burn numbers that track your effort, you pretty much need to use a power meter. If you are, say, trying to lose weight by managing calories and you use some of the computers and their algorithms, you're going to gain weight at a rapid pace by using some of the methods out there.

J.

zacster

But that's the thing, I do have a power meter so why doesn't RWGPS just use that number? And when I rode without the PM I got a high number, but with the PM it estimated a low number? It just doesn't make sense. In any case, I take all of it with a grain of salt. I did a calculation last year, added up all of my calories, divided by 3500, and it was the exact amount of my weight loss. 3500 is an approximate amount of calories in 1 pound of fat. I'm sure you could pick this apart, but on a ballpark calc it was close enough to reality. This assumes too that my diet is perfect, just enough calories to get me through the day without gaining or losing weight. I made no such attempt to keep my diet that way.

DrIsotope

Ignore the calorie count altogether and just go off of total work, expressed in kJ. There's no algorithm applied to it.

JohnJ80

I'm not sure that RWGPS can even talk to a power meter in any meaningful way but even if it could, it's a navigation program not a bike computer program. There are far better choices than that.

When I looked at this a few years ago, Cyclemeter on the iPhone was about 2X what Strava was saying. Garmin, Wahoo, all were somewhere in the middle. They were worse without either an HRM or a power meter and progressively got better as each of those were added but still were higher than Strava which I think is closer to accurate. At this point, I pretty much ignore any calorie number in anything other than Strava (which was the most conservative of all) but still just think of that as more of a figure of merit than anything accurate.

If you mean adding up the calories shown on the bike computer and dividing by 3500 - if that matched anything it was pretty much pure dumb luck.

I agree with this.

CadenceCrazy

I maintain a ride database that captures three different and probably totally inaccurate calorie burns. One source is a heart rate monitor, the second Ride With GPS, and the third a formula I found somewhere on the web. Granted, none of the three are probably very accurate but the trend data for similar rides could have value. Surprisingly, the HRM and RWGPS numbers are usually extremely close, frequently within 75 cals for a two hour ride. Both devices probably use a very similar but still inaccurate algorithm. A power meter would be the gold standard but I don't put out enough watts to light a refrigerator and can't justify the expense. In any case, the scale doesn't lie.

TimothyH

The idea of trending is important and the fact that the HRM and RWGPS are close is interesting.

HRM based calories are not as accurate as an power meter but those who claim that the numbers are completely useless fail to recognize that it is an order of magnitude tool. Uncertainty is a given for order of magnitue tools and estimates. The claim to absolute accuracy isn't made and the numbers can be useful as an estimate, especially in the beginning of a project or effort, for trending or to keep track of diet and exercise for the sake or consistency.

Personally, I don't care if the numbers are 20% or even 50% off as long as they are consistent and the bathroom scale agrees. Once I've lost (or gained) some weight I begin to understand how much I can eat and how much exercise I have to do to lose, gain or maintain weight.


-Tim-

JohnJ80

Well, when one app says 1200 cal for an hour and the other more realistic one says 500 (bit you don’t know which is the right one) you’re going to be gaining weight as part of your effort to hone in on the number as a figure of merit. Good luck with that.

DrIsotope

As of the latest firmware (that is, just this week,) Wahoo apparently now discards power data entirely in their calorie calculations. With the Bolt, if my avg. heartrate is less than 65% of max, kcal expended is derived by using an algorithm based on basal metabolic rate:

BMR = 66 + (13.7 * weightKg) + (5 * heightCm) - (6.8 * ageYears)

As my chest strap HRM is a few years old, it can sometimes take about a mile or so to connect with the head unit, so I get absolutely nothing for the first mile-- the kcal screen will just sit on zero.

So combining HR data with dumb algorithms results in me burning absurdly low amounts of calories-- yesterday was 34 miles w/ ~1,000ft of vertical @ 16.8mph: 1,168kJ, 845kcal, or 25kcal.mi.
Today was an even more leisurely 22.5 miles w/ 659ft @ 15.9mph: 723kj, 587kcal, or 26kcal/mi. I climbed less, went slower, and burned more per mile.

So this is great for people without PMs, and not so great for people with. Either that or I've become really, really efficient. I'm wondering what the Bolt does if I just leave the HRM at home.

surak

I switched from a Garmin Edge to a Bolt this year and noticed ludicrously higher calorie estimates. I have a PM and every other platform agreed within a few percentage points on my rides. The Bolt's estimates are more than 50% higher. Plus I found out that platforms like Strava will now just blindly accept the Bolt's figure. Thanks, Wahoo.

DrIsotope

Yeah, it's pretty terrible. Why anyone would choose to feed an HRM through an algorithm while completely ignoring power data is beyond me.

JohnJ80

Thanks for the information. That’s just terrible on the part of Wahoo. One would think that if the computer was receiving power data, it would just use that. That’s one of the reasons I bought a power meter in the first place. A pox on Wahoo for this.

J.

DrIsotope

Wahoo has had a real bad string of firmware updates lately, but none so bad as this. I’m going to leave the HRM at home on Saturday and see what happens. I think Strava defaults to the kJ from the PM for calories/work done, and only uses the HR data for Relative Effort (formerly Suffer Score.) I’m curious as to what’s going to show up in the Wahoo companion app.

bobwysiwyg

Received a Bolt for Xmas. Took my first outside ride with it a week or so ago. I rode a familiar route that I've ridden often. Came back, checked the results and was convinced Wahoo had a "dream setting" for calories .

DrIsotope

From Wahoo Support:

"We have not changed this algorithm for several years, so if something changed recently, it's probably due to something changing on the Profile page of the app. I would recommend logging out and back in to the ELEMNT app and then updating your profile metrics (height, weight, heart zones etc).

We are currently working on a calorie algorithm that utilizes KJ data, but for the time being your best bet is either to make sure your heart rate zones are correct, or to simply use the KJ number (plus 10 or 15 percent) for your calories burned."

Nice try Wahoo, but your magical algorithm magically agreed with my PM for more than a year, now just all of a sudden decided I'm super efficient? Their response also utterly ignores the fact that when the data gets imported into say, Apple Health, Health just takes it for what it is, high or low. I cannot believe that Wahoo has never used the PM for calorie data. I looked at a few rides from previous weeks, and it was not uncommon for the Wahoo calories to be within 1% of the kJ total-- yet I've never had one of those instances where the kcal number is stratospherically higher than the kJ.