How much can Strava's calorie burn count be trusted?

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.

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...

it’s explained a bit in this article.

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. 

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/

https://www.trainingpeaks.com/blog/how-accurate-is-that-calorie-reading/

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

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/

https://www.trainingpeaks.com/blog/how-accurate-is-that-calorie-reading/

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. 

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

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!

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.

madcarew wrote:

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.