Calories spent whilst cycling

markwb79

I see loads of different (over) estimations on various websites.
I rode yesterday for 160km. I used a SRM and my Garmin, these are the results:

SRM - 3676kj = 878kcal (from GC)
Garmin - 2538 calories

Am I missing something? These seem wildly different?

Thanks
Mark

amaferanga

What's GC? Garmin Connect or Golden Cheetah? I think you've misunderstood something cos kJ is approximately equal to kCal so you burnt around 3700kCal.

Unfortunately Garmin logic means that on some devices (the FR 310XT and Edge 500 and probably others), if an HR monitor is present then they ignore the power data and use their HR-based calorie guessing algorithm to compute calories. If no HR monitor is present they use the kJ figure to compute calories.

markwb79

sorry, I meant Golden Cheetah.

That would explain it, I google converting kj to kcal and they all come up with calculators that say the same as above?

I didnt connect the power to my Garmin actually. So it is based on HR, not power

Tom Dean

The figure you have from your SRM is the energy you put out, not what you 'spent' to do it.

Using joules out = calories in gives an estimate based on the body's efficiency being roughly the same as the actual joules/calories conversion rate, ~23%.

Pokerface

Tom's explanation lost me a little... but I think he's got it right.

The simplest answer is to look at your SRM work in kJ and use that as your calories burned estimate. It won't be far off.

Garmin is rarely correct for calorie estimates.

phreak

I've always used approximately 600 calories an hour as a decent rule of thumb on an endurance ride. Obviously that might vary depending on how hard you go, but it's likely to put you in the right ball park.

FatTed

I usually think of it as about 20-23 Calories per Km for a conversational ride, which is in the ball park for OP and Phreak

ut_och_cykla

phreak wrote:

I've always used approximately 600 calories an hour as a decent rule of thumb on an endurance ride. Obviously that might vary depending on how hard you go, but it's likely to put you in the right ball park.

+1 really pootling perhaps less than half of this for me, and going at a reasonable pace (for me) I'd be unlikely to hold 600kcal hour after hour - maybe 2-3 but not more. But then I am female 50 + & BMI 24.

Pokerface

Part of the magic of using an SRM (or any power meter) is that you don't have to 'guess' how many calories you've used. Power output doesn't lie. Just convert the the kJ used in power output to calories burned and you're done.

If you don't have a power meter, then yes, good rule o thumb is around 600 calories an hour for a steady ride. 800-1000 for full-on racing. And 400-600 for an easy/group ride.

Setarkos

Tom Dean wrote:

The figure you have from your SRM is the energy you put out, not what you 'spent' to do it.

Using joules out = calories in gives an estimate based on the body's efficiency being roughly the same as the actual joules/calories conversion rate, ~23%.

This is the correct explanation.

Say you generate 1000 kJ on your ride, your body has an efficiency of roughly 23% let's say 25% for simplicity.
So your body needs 4000 kJ to generate those 1000 kJ. Now 1000 kJ = 250 kcal (roughly) <=> 4000 kJ = 1000 kcal.
Hence 1000 kJ output means 1000 kcal burnt.

Theoretically your basal metabolic rate needs to be added on top of that.

ric/rstsport

Pokerface wrote:

Part of the magic of using an SRM (or any power meter) is that you don't have to 'guess' how many calories you've used. Power output doesn't lie. Just convert the the kJ used in power output to calories burned and you're done.

If you don't have a power meter, then yes, good rule o thumb is around 600 calories an hour for a steady ride. 800-1000 for full-on racing. And 400-600 for an easy/group ride.

+1, although i have people i coach where a quality endurance ride works out approx double the 600/hr (~1200/hr) you're suggesting

the main trouble is working out how much you eat (not you personally colin). anyone!

Pokerface

Ric/RSTSport wrote:

Pokerface wrote:

Part of the magic of using an SRM (or any power meter) is that you don't have to 'guess' how many calories you've used. Power output doesn't lie. Just convert the the kJ used in power output to calories burned and you're done.

If you don't have a power meter, then yes, good rule o thumb is around 600 calories an hour for a steady ride. 800-1000 for full-on racing. And 400-600 for an easy/group ride.

+1, although i have people i coach where a quality endurance ride works out approx double the 600/hr (~1200/hr) you're suggesting

the main trouble is working out how much you eat (not you personally colin). anyone!

1200 calories an hour in training? Does that not equate to around 330w per hour?

ric/rstsport

it does

SBezza

My endurance rides are in the 800KCal per hour area, as like Ric says it really does depend on what power you put out.

Working out how much you eat can be very anal, but if you get used to how much food weighs, you can esitmate fairly good how much a meal is in terms of calories.

T_Pucker

Pokerface wrote:

Ric/RSTSport wrote:

Pokerface wrote:

Part of the magic of using an SRM (or any power meter) is that you don't have to 'guess' how many calories you've used. Power output doesn't lie. Just convert the the kJ used in power output to calories burned and you're done.

If you don't have a power meter, then yes, good rule o thumb is around 600 calories an hour for a steady ride. 800-1000 for full-on racing. And 400-600 for an easy/group ride.

+1, although i have people i coach where a quality endurance ride works out approx double the 600/hr (~1200/hr) you're suggesting

the main trouble is working out how much you eat (not you personally colin). anyone!

1200 calories an hour in training? Does that not equate to around 330w per hour?

Yes, that's what a real elite cyclist does.

800-1000 calories for full on racing? Jesus wept.

esafosfina1

FFS, just ride your bikes and enjoy it... no one on here is in line to win a Grand Tour, a world championship, so be realistic and balance your input/output... it's not hard people.

ric/rstsport

esafosfina1 wrote:

FFS, just ride your bikes and enjoy it... no one on here is in line to win a Grand Tour, a world championship, so be realistic and balance your input/output... it's not hard people.

that's not true

esafosfina1

Ric/RSTSport wrote:

esafosfina1 wrote:

FFS, just ride your bikes and enjoy it... no one on here is in line to win a Grand Tour, a world championship, so be realistic and balance your input/output... it's not hard people.

that's not true

Enlighten me...

ric/rstsport

try looking at pokerface...

esafosfina1

Ric/RSTSport wrote:

try looking at pokerface...

FFS, no offense to pokerface, and if he wants to get into it, PM me mate... get a grip... if you realise that what I'm saying is the simple and irrefutable fact... calories in vs calories out. It's not a hard concept to conceive...

And, as you have brought it up... try looking at esafofina1 a little closer. (Ffs, I hate having to to do this but once in a while you get someone that needs a wake-up call...)

ric/rstsport

i know its u sturge. not sure of ur point tho? we know its energy in/out

esafosfina1

Ric/RSTSport wrote:

i know its u sturge. not sure of ur point tho? we know its energy in/out

Point? I was simply stating that 'most' on here take it too seriously for their own good... few and far between will ever get to a stage whereby a 'stripey-jersey' or 'GT' is in their sights... so if I missed Colin in that statement I apologise, I was trying (obviously mistakenly) to offer a more staid and level appraisal.

What were we arguing about anyway...?

ric/rstsport

i disagree, CS (sorry i'm referring to you as CS so as not to confuse you with pokerface). While you're correct, it's simply calories in versus out (or energy in versus out) - the OP was asking for clarity on the data produced by a power meter, and we were trying to explain that and then discuss other related things. i can't see anything wrong with that and don't see the need to keep those things only for people who are elites or potential world champions (if that was the case i shouldn't have a dura ace equipped bike and should probably make do with a 3 speed sturmey archer bike as i'm essentially not very good in the grand scheme of things).

we have information available to us, and if we want we should use it. it provides a return and can make things better or enable such things as speeding up weight loss if used correctly. or for training harder. or for working out aerodynamics, etc.