I did the Four Horsemen route in Zwift yesterday and Strava thinks I burned 2400+ calories.  I know I was drained and needed a quick nap after eating some lunch afterwards, but that seems pretty unbelievable.  How much can I trust that?  I was using a smart trainer w/power meter (CycleOps H2) and had a HR monitor on at the time.

madcarew [1002 posts] 7 months ago
6 likes

2400 (k)Cal isn't a huge amount of calories. There's 2 measures: one is the amount of power (for the duration) used in the activity, and the other is the amount of calories used by the body to produce that power. The second measure is 4.5 times higher than the other.

On a flat road on a road bike in normal conditions 200w output is +/- 30 kph. 200W is a 200 joules / second which is 47 calories / sec or 171 kcal per hour (kCal is our food 'calories'). In general, humans are 21 - 23% efficient so to produce 171 kcal of output they burn 750 - 800 kcal per hour.  You can use this as a guideline to figure which measure strava is using. Pros can put out about 300w  for several hours (using 1300 - 1400 kcal / hr) whereas mere (male) mortals are generally going to be in the 180 - 200w for a sportive. Females are typically 75% of that.

DoctorFish [200 posts] 7 months ago
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My calorie burn, for a 83kg 43 year old, according to my Wahoo Elment and heart rate monitor comes out at around 900 kCal an hour when I feel I'm pushing myself and 800 kCal an hour when I feel I'm taking it a bit easier.

This is for riding a road bike on the road, rather than using a trainer.

It ties in fairly well with values that I've found elsewhere such as https://www.myfitnesspal.com/exercise/lookup

fenix [1188 posts] 7 months ago
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There is a running calculator I trust that gives about 100 calories per mile run for the averag sized bloke.  So if I'm running then 800-900 calories an hour is believable.

If I'm cycling its got to be a lot less than that.  Some of the strava claims are ridiculously high. You'd not want to use those as part of a dieting regime !

iso2000 [116 posts] 7 months ago
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I ignore it. On a ride I may eat 500 calories and when I get home 2 or 300 more than if I had been sedate. But Strava tells me I have burnt 2500 calories on a ride. Wouldn’t such a calorie deficit make me ill or super skinny? I stick to the rule that I burn 400 calories per hour on the bike.

Simon E [3738 posts] 7 months ago
1 like

I would ignore any such machine / software algorithm, there are too many variables they can't account for. Also the type of food you eat and when you eat it is more important than the kcal numbers on the packet and anyway they can vary quite a bit from those figures.

https://www.trainingpeaks.com/blog/a-calorie-is-not-a-calorie/

The most reliable indicator is your trouser waistband or belt, that will tell you if you're losing or gaining weight (or fat).

Jimmy Ray Will [1022 posts] 7 months ago
1 like
iso2000 wrote:

I ignore it. On a ride I may eat 500 calories and when I get home 2 or 300 more than if I had been sedate. But Strava tells me I have burnt 2500 calories on a ride. Wouldn’t such a calorie deficit make me ill or super skinny? I stick to the rule that I burn 400 calories per hour on the bike.

But doing so, you are knowingly sticking with something that you know is wrong... interesting view point. 400kcals an hour is smashing out ~110watts an hour. that is very sedate for nearly everyone. You will be burning more.

Jimmy Ray Will [1022 posts] 7 months ago
0 likes
Simon E wrote:

I would ignore any such machine / software algorithm, there are too many variables they can't account for. Also the type of food you eat and when you eat it is more important than the kcal numbers on the packet and anyway they can vary quite a bit from those figures.

https://www.trainingpeaks.com/blog/a-calorie-is-not-a-calorie/

The most reliable indicator is your trouser waistband or belt, that will tell you if you're losing or gaining weight (or fat).

Interestingly, the longer and more circular your route, the more accurate the estimation will be. The estimations make some fairly hefty assumptions, such as likely weight of bike, rolling resistance, assumes still conditions etc. All of thes things can skewer calorific burn significantly.However on rides over 2 hours, you can safely wager that then estimated burn will be pretty damn close to actual.

I'd argue, that in and around extended exercise, kcal numbers are more influential than calorie quality. Exercise reduces insulin response, and your burn will negate the potentially negative effect of eating high GI foods.

Jimmy Ray Will [1022 posts] 7 months ago
0 likes

2400 (k)Cal isn't a huge amount of calories. There's 2 measures: one is the amount of power (for the duration) used in the activity, and the other is the amount of calories used by the body to produce that power. The second measure is 4.5 times higher than the other.

On a flat road on a road bike in normal conditions 200w output is +/- 30 kph. 200W is a 200 joules / second which is 47 calories / sec or 171 kcal per hour (kCal is our food 'calories'). In general, humans are 21 - 23% efficient so to produce 171 kcal of output they burn 750 - 800 kcal per hour.  You can use this as a guideline to figure which measure strava is using. Pros can put out about 300w  for several hours (using 1300 - 1400 kcal / hr) whereas mere (male) mortals are generally going to be in the 180 - 200w for a sportive. Females are typically 75% of that.

A more simple equation I work to, and seems to be pretty accurate, is that the KJoule / Kcal equation is pretty much bang on, when you factor in human efficiency. So if you are banging out 100w, you are smashing through 360kcals an hour.

KnowThyInnerTube [11 posts] 7 months ago
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Whatever happened to the two equations I have used for a good while, and that seem to agree with my Garmin HRM and Strava estimates? They are as follows:

Running - 0.75 cal per kg of running wieght per kilometre.

Cycling - 0.25 cal per kg of cycling weight per kilometre.

Try them out and see if you really do need that extra banana on the handlebars!!!

KnowThyInnerTube [11 posts] 7 months ago
0 likes

Whatever happened to the two equations I have used for a good while, and that seem to agree with my Garmin HRM and Strava estimates? They are as follows:

Running - 0.75 cal per kg of running wieght per kilometre.

Cycling - 0.25 cal per kg of cycling weight per kilometre.

Try them out and see if you really do need that extra banana on the handlebars!!!

antigee [550 posts] 7 months ago
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I'd prefer it if effort was measured in "beer credits" .....though I like the simplicity of KnowThyInnerTubes' calcs - seems to me they ignore exertion level - certainly using a polar device I've seen different answers for the same ride based on if I've bothered to wear it or not so I assume theri calcs involve HR as a measure of exertion

as to OP's question google tells me the Zwift Four Horseman is 55miles (for those that use them?) so 2400kcals wouldn't surprise if this is true

just read Mark Beaumonts 80days book and getting in enough cals was a serious problem

Judge dreadful [344 posts] 7 months ago
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I work on about 23 Kcal per mile. That seems about right.

clayfit [137 posts] 7 months ago
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I think that they normally work on the basis that the body is 25% efficient, so that you burn 4x more calories than you put out in power through the pedals. On that basis 250W through the pedals burns 1 kilowatt hour of energy per hour, which is 860 kcal/hour.   That seems in line with sense and physiology, and what is estimated to be burned at other workrates and in other sports.

My Garmin estimates about 20% more energy burned than I measure using the Powertap.

It also begs the question, which I don't have the answer to, of how to make your body more efficient (for speed/endurance) or less efficient (for weight loss).

andyp [1600 posts] 7 months ago
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Not in the slightest. See also: any other form of 'calories burnt' estimate.

iso2000 [116 posts] 7 months ago
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I'm still ignoring it. On recent ride where my moving time was 4 hours Strava tells me I burnt 3,759 calories, 940 calories per hour (btw that is over half what a TDF rider is estimated to burn). On a fairly demanding trainer road seession of 1 hour (Diamond Valley Road Race) I burnt 456 calories.

The difference? The indoor session was on a smart trainer with a power meter and I do not have a power meter on my bike. My conclusion, if you have a power meter then Stava's calorie figure may be fairly accurate but if not ignore it.

I seem to remember reading an article blaming sports apps for over estimating calories burnt which leads to people who exercise not losing weight, wish I'd saved the link.

fukawitribe [2821 posts] 7 months ago
1 like

As others have alluded to more or less - don't rely on it and don't fret it, it's almost entirely nonsense.

madcarew [1002 posts] 7 months ago
0 likes

I think that they normally work on the basis that the body is 25% efficient, so that you burn 4x more calories than you put out in power through the pedals. On that basis 250W through the pedals burns 1 kilowatt hour of energy per hour, which is 860 kcal/hour.   That seems in line with sense and physiology, and what is estimated to be burned at other workrates and in other sports.

My Garmin estimates about 20% more energy burned than I measure using the Powertap.

It also begs the question, which I don't have the answer to, of how to make your body more efficient (for speed/endurance) or less efficient (for weight loss).

[/quote

Make it more efficient for riding: Training and practise - massive increases available

How to make it less efficient for weight loss: Changing your diet around makes you less effective at extracting calories from the food you eat. Minor efficiencies available.

Judge dreadful [344 posts] 7 months ago
0 likes
clayfit wrote:

It also begs the question, which I don't have the answer to, of how to make your body more efficient (for speed/endurance) or less efficient (for weight loss).

if you want to make your body more efficient, make your power at a higher Cadence ( 85 - 100 rpm for argument’s sake ) if you want less efficiency make your power at lower Cadence ( sub 60 rpms, for argument’s sake ) This is quite dependent on your ability to make sufficient power at the higher Cadence to not make it purely a leg flapping exercise, say (for example ) circa 200 Watts at 90 rpm for more efficient, circa 200 Watts at 60 odd rpms for less efficiency.

https://www.active.com/cycling/articles/why-fast-pedaling-makes-cyclists...

Jimmy Ray Will [1022 posts] 7 months ago
0 likes
KnowThyInnerTube wrote:

Whatever happened to the two equations I have used for a good while, and that seem to agree with my Garmin HRM and Strava estimates? They are as follows:

Running - 0.75 cal per kg of running wieght per kilometre.

Cycling - 0.25 cal per kg of cycling weight per kilometre.

Try them out and see if you really do need that extra banana on the handlebars!!!

Those equations do not factor in intensity at all. This is less relevant for running as wind resistance doesn't kick in until about 12mph, so if you run slower, it takes longer to complete the kilometre so it evens out... assuming on the flat.

Morat [340 posts] 7 months ago
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Simon E wrote:

The most reliable indicator is your trouser waistband or belt, that will tell you if you're losing or gaining weight (or fat).

My belt was very reliable until it shrank

Grahamd [1030 posts] 7 months ago
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Morat wrote:
Simon E wrote:

The most reliable indicator is your trouser waistband or belt, that will tell you if you're losing or gaining weight (or fat).

My belt was very reliable until it shrank

Think I bought the same belt!