Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Electronics, Lighting, & Gadgets HRM, GPS, MP3, HID. Whether it's got an acronym or not, here's where you'll find discussions on all sorts of tools, toys and gadgets.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 10-28-13, 05:58 AM   #1
smurray
Senior Member
Thread Starter
 
smurray's Avatar
 
Join Date: Jan 2006
Location: Toledo, OH
Bikes: Leader 722TS, Surly Steamroller, Panasonic DX-3000, Trek 4900
Posts: 490
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Calories Burned: Strava vs Runkeeper vs Endomono

I use Strava on my iPhone to log my daily bike commute to and from work. I then use tapiriik.com to sync my Strava account to all the various sites I use (Runkeeper, Endomondo, Garmin Connect, etc...). I noticed today that there is a huge difference in estimated calories burned between Strava and the other sites. For example, this morning I rode for just under 50 minutes and went 11.2 miles. Strava calculates that I burned 281 calories during the ride, Runkeeper estimates 526 calories, and Endomondo estimates 555 calories. All three sites have the same info in terms of my height/weight/age and they are all reporting about the same distance/time/average speed. I know that all of these sites can't give anything more than a rough estimate without HR data, but why would Strava be estimating so much lower than the other two, and which is most likely to be correct?
smurray is offline   Reply With Quote
Old 10-28-13, 07:15 AM   #2
kingsqueak
Senior Member
 
Join Date: Jul 2013
Location: NJ cellphone central
Bikes: Surly Ogre // (old and gone) Cannondale ST400, Rockhopper Sport
Posts: 468
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
With HR data it's a wild estimate...without it's more of a guess.

Power + HR is closer, but without metabolic data for the individual still just an estimate.

I look at calories burned as a coarse estimate of effort/output but don't consider it further.
kingsqueak is offline   Reply With Quote
Old 10-28-13, 08:33 AM   #3
Looigi
Senior Member
 
Looigi's Avatar
 
Join Date: Dec 2010
Bikes:
Posts: 8,942
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Of course it depends on many factors but IMO, Cal burn for 50 min and 11.2 miles on flat/undulating terrain is more in line with the low Strava estimate, most definitely not near 500 Cal.
Looigi is offline   Reply With Quote
Old 10-28-13, 08:50 AM   #4
pdlamb
Senior Member
 
Join Date: Dec 2010
Location: northern Deep South
Bikes: Fuji Touring, Novara Randonee
Posts: 2,705
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 28 Post(s)
Best calorie calculator is your body, but it lacks an LCD readout. Everything else is just a guess.

That said, I second Looigi's opinion. The Strava estimate seems reasonable, the others seem optimistic unless you're 500 pounds riding a rust bucket with massive MTB tires.
pdlamb is offline   Reply With Quote
Old 10-28-13, 08:50 AM   #5
smurray
Senior Member
Thread Starter
 
smurray's Avatar
 
Join Date: Jan 2006
Location: Toledo, OH
Bikes: Leader 722TS, Surly Steamroller, Panasonic DX-3000, Trek 4900
Posts: 490
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Looigi View Post
Of course it depends on many factors but IMO, Cal burn for 50 min and 11.2 miles on flat/undulating terrain is more in line with the low Strava estimate, most definitely not near 500 Cal.
Only other factor I forgot to mention was I ride a fixed gear bike so there is no coasting. Gear ratio is 48/19 w/ 25c tires. Neither Strava or any of the others have any of that data though so I'm still not sure why there's such a huge discrepancy.
smurray is offline   Reply With Quote
Old 10-28-13, 09:02 AM   #6
smurray
Senior Member
Thread Starter
 
smurray's Avatar
 
Join Date: Jan 2006
Location: Toledo, OH
Bikes: Leader 722TS, Surly Steamroller, Panasonic DX-3000, Trek 4900
Posts: 490
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Here's the ride in question.
smurray is offline   Reply With Quote
Old 10-28-13, 06:15 PM   #7
zacster
Senior Member
 
Join Date: Jul 2004
Location: Brooklyn NY
Bikes:
Posts: 4,967
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Having just joined Strava 2 weeks ago, and having just bought an HRM/GPS watch last week, I'm somewhat mystified myself by the Strava and Garmin numbers I get. A quick 20 mile ride in the park gave me 950 calories, a strenuous 57 mile ride with climbing gave me ~2000. Something isn't right about that.
zacster is offline   Reply With Quote
Old 10-28-13, 06:49 PM   #8
cccorlew
Erect member since 1953
 
cccorlew's Avatar
 
Join Date: Dec 2006
Location: Antioch, CA (SF Bay Area)
Bikes: Roubaix Expert, Motobecane Ti Century Elite turned commuter, Cannondale F500 Mtn bike, Some old French thing gone fixie
Posts: 6,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Quote:
Originally Posted by kingsqueak View Post
With HR data it's a wild estimate...without it's more of a guess.

Power + HR is closer, but without metabolic data for the individual still just an estimate.

I look at calories burned as a coarse estimate of effort/output but don't consider it further.
How can having a power meter be anything but near perfect? I mean, it's actually measuring the power you use. That maps to energy pretty darn closely doesn't it?

My PowerTap reports pretty close to what Strava guesses on most rides. Strava can't tell about wind, or my pannier laden commuter bike, but it's great for most road rides.
All others -- Garmin, Ascent, MyFitnessPal -- seem wildly optimistic about how many calories get burned.
cccorlew is offline   Reply With Quote
Old 10-28-13, 06:54 PM   #9
kingsqueak
Senior Member
 
Join Date: Jul 2013
Location: NJ cellphone central
Bikes: Surly Ogre // (old and gone) Cannondale ST400, Rockhopper Sport
Posts: 468
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Power gets your power out more correctly, still calories burned while producing that power will vary person to person. Some will burn less, some more.
kingsqueak is offline   Reply With Quote
Old 10-29-13, 08:34 AM   #10
NeilMyers
Junior Member
 
NeilMyers's Avatar
 
Join Date: Oct 2013
Bikes:
Posts: 21
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by kingsqueak View Post
Power gets your power out more correctly, still calories burned while producing that power will vary person to person. Some will burn less, some more.
I have always wondered how this all works. Would I be correct to assume the power measured on a power meter (assuming it is working correctly) is the minimum amount of power your body would need to expend to produce that power? Or are the two measuring completely different things? Trying to understand how this works ...
NeilMyers is offline   Reply With Quote
Old 10-29-13, 09:00 AM   #11
njkayaker
Senior Member
 
Join Date: Sep 2007
Bikes:
Posts: 9,479
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 61 Post(s)
Quote:
Originally Posted by NeilMyers View Post
I have always wondered how this all works. Would I be correct to assume the power measured on a power meter (assuming it is working correctly) is the minimum amount of power your body would need to expend to produce that power? Or are the two measuring completely different things? Trying to understand how this works ...
Yes.

Power meters measure power output. Not the power input into the system.

You would actually have to produce more power than is output because of losses between you and the wheels.

Last edited by njkayaker; 10-29-13 at 09:05 AM.
njkayaker is offline   Reply With Quote
Old 10-29-13, 09:11 AM   #12
NeilMyers
Junior Member
 
NeilMyers's Avatar
 
Join Date: Oct 2013
Bikes:
Posts: 21
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by njkayaker View Post
Yes.

Power meters measure power output. Not the power input into the system.
Understood, but unless we've discovered a perpetual motion machine, doesn't the power input have to be the same or more than the power output (the difference being lost to friction, and other inefficiencies)?

In other words, one would expect the calories burned to be related to the power measured by your power meter.

As I said, this is interesting to me so I did a quick Google search. Here is an excellent article on the subject. In this article the author explains that the body is actually horribly inefficient at converting food to energy ... about 76% of the energy is lost to things like heat. He explains that if you convert the power meter readings to calories, and then account for these inefficiencies, you get a very good approximation of calories burned to produce that power. The example he gives is a rider who maintains 300 watts for an hour has burned 1,000 calories to generate that power.

I love forums ... you learn something every day!
NeilMyers is offline   Reply With Quote
Old 10-29-13, 09:17 AM   #13
njkayaker
Senior Member
 
Join Date: Sep 2007
Bikes:
Posts: 9,479
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 61 Post(s)
Quote:
Originally Posted by NeilMyers View Post
Understood, but unless we've discovered a perpetual motion machine, doesn't the power input have to be the same or more than the power output (the difference being lost to friction, and other inefficiencies)?
Yes (that's what I was implying). I updated my post (before you replied) to make it clear.

Calories burned > power output.

Or:

Calories burned = power output + power loss.

Quote:
Originally Posted by NeilMyers View Post
In other words, one would expect the calories burned to be related to the power measured by your power meter.
Yes. It's related. Note that the efficiency (calories burned compard to power output) isn't going to be constant for a single individual (and, certainly, different people will likely have different efficiencies). Note that you are also burning calories for purposes other than driving the bike (eg, keeping warm).

Quote:
Originally Posted by NeilMyers View Post
As I said, this is interesting to me so I did a quick Google search. Here is an excellent article on the subject. In this article the author explains that the body is actually horribly inefficient at converting food to energy ... about 76% of the energy is lost to things like heat. He explains that if you convert the power meter readings to calories, and then account for these inefficiencies, you get a very good approximation of calories burned to produce that power. The example he gives is a rider who maintains 300 watts for an hour has burned 1,000 calories to generate that power.

I love forums ... you learn something every day!
The effiiciency isn't constant in one person (76% is some sort of average). And some people are more efficient than others.

Power losses:

metabolic inefficiencies.
technique inefficiencies.
mechanical losses (friction/flexing).

Last edited by njkayaker; 10-29-13 at 09:25 AM.
njkayaker is offline   Reply With Quote
Old 10-29-13, 09:30 AM   #14
NeilMyers
Junior Member
 
NeilMyers's Avatar
 
Join Date: Oct 2013
Bikes:
Posts: 21
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by njkayaker View Post
Yes. It's related. Note that the efficiency (calories burned compard to power output) might not be constant for a single individual (certainly, different people will likely have different efficiencies).
You would think so. However, the article says the efficiency rate is remarkably constant and always close to 24%, regardless of the individual. I found that very interesting.

Quote:
Originally Posted by njkayaker View Post
Note that you are also burning calories for purposes other than driving the bike (eg, keeping warm).
True, but what most people are interested in is how many extra calories did I burn on this or that ride. That is what the power meter tells you (indirectly).

Quote:
Originally Posted by njkayaker View Post
Power losses:

technique inefficiencies.
mechanical losses (friction/flexing).
I don't believe those come into play in this discussion. Yes, those may affect how much of your power is converted into speed, but whether the power was effective or ineffective from a cycling perspective, it is still power you generated and that came from calories you burned.
NeilMyers is offline   Reply With Quote
Old 10-29-13, 09:38 AM   #15
Looigi
Senior Member
 
Looigi's Avatar
 
Join Date: Dec 2010
Bikes:
Posts: 8,942
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
""Converting watts to Calories

A 1 watt work rate
= 1 joule / second
= 3.6kJ/hour

There are 4.184 joules in 1 calorie
Therefore:

a 1 watt work rate
= 0.239 calories / sec
= 860.4 calories / hr
= 0.8604 kilocalories / hr
(kilocalories are usually expressed as capital 'C' Calories when talking about human nutrition and energy expenditure)

therefore, an energy expenditure rate of 1 Calorie/hr
= 1/0.8604 watts
= a work rate of 1.16 watts

The human body is around 20-25% efficient at converting food energy into mechanical energy. Digestion and absorption are energy intensive processes. The conversion of absorbed fats, carbs, and amino acids into the muscle's final energy molecule, adenosine triphosphate (ATP), is also energy intensive.

Based on this, the energy expended to create n watts at the pedal is thus::

100 watts = 0.864 * 100 / .24 = 358.5 Cals / hr = 1500 kJ /hr
150 watts = 537.8 Cals / hr
200 watts = 717 Cals / hr""

From: http://brisbanebike.blogspot.com/201...d-cycling.html
Looigi is offline   Reply With Quote
Old 10-29-13, 09:42 AM   #16
lsberrios1 
Senior Member
 
lsberrios1's Avatar
 
Join Date: Jul 2012
Location: Atlanta GA
Bikes: '13 Spech Roubaix SL4 Expert
Posts: 2,475
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Quote:
Originally Posted by cccorlew View Post
How can having a power meter be anything but near perfect? I mean, it's actually measuring the power you use. That maps to energy pretty darn closely doesn't it?

My PowerTap reports pretty close to what Strava guesses on most rides. Strava can't tell about wind, or my pannier laden commuter bike, but it's great for most road rides.
All others -- Garmin, Ascent, MyFitnessPal -- seem wildly optimistic about how many calories get burned.
Strava uses your power meter data once it is set up to indicate calories (maybe only in the paid version).

For me an hour stroll at about 13-14mph on a 30'/mile terrain is about 300 cal (this is zone 1 recovery pace of less that 140watts). The same ride at 19+mph solo (z4 230+watts). is about 750 cal. Intensity definitely varies but calories can only be accurately measured with a Power meter. I had reached a plateau in weight loss until I got the power meter. Now I know exactly what I shed everytime I work out and pounds just come off since I can measure it accurately against my food intake.

Also, I've found out that comparing HR data and power data for calories burner HR data usually comes at 20% high. So if you go by "heart" a good guess would be to multiply the estimate given by 80% +/-. Of course that may vary depending on your cardiovascular condition and might be only specific to me.

When it comes to weightloss it is always better to underestimate calories burned and overestimate calories consumed if you are not 100% certain.
__________________
Cat 6 going on PRO....

Last edited by lsberrios1; 10-29-13 at 09:49 AM.
lsberrios1 is offline   Reply With Quote
Old 10-29-13, 09:45 AM   #17
lsberrios1 
Senior Member
 
lsberrios1's Avatar
 
Join Date: Jul 2012
Location: Atlanta GA
Bikes: '13 Spech Roubaix SL4 Expert
Posts: 2,475
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Quote:
Originally Posted by Looigi View Post
""Converting watts to Calories

100 watts = 0.864 * 100 / .24 = 358.5 Cals / hr = 1500 kJ /hr
150 watts = 537.8 Cals / hr
200 watts = 717 Cals / hr""

From: http://brisbanebike.blogspot.com/201...d-cycling.html
Yup. A better summary of what I meant to say. so take it that for a regular person at a leisurely pace it is 350 calories per hour. At an intense pace it is around 650 to 700 per hour.
__________________
Cat 6 going on PRO....
lsberrios1 is offline   Reply With Quote
Old 10-29-13, 09:49 AM   #18
njkayaker
Senior Member
 
Join Date: Sep 2007
Bikes:
Posts: 9,479
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 61 Post(s)
Quote:
Originally Posted by NeilMyers View Post
You would think so. However, the article says the efficiency rate is remarkably constant and always close to 24%, regardless of the individual. I found that very interesting.
It does make that claim (though we don't really know what "remarkably constance and always close" means. We don't know if it's correct. Note that the article is talking about efficiency with respect to calories burned. That's not that interesting compared to actually moving the bike.

That is, supposing the variation is +-2%, that different is negligiable with respect to calories burned.

But it is much more significant as a component of power production (2% of the total calories burned is 8% of the power being used to drive the wheels).

According to this, shivering consumes 425 watts and cycling at 13–18 km/h consumes 400 watts (larger than what the power meter would show). If those numbers are correct, then the variation of calories consumed and power produced can be very different than 24% (it's going to be much smaller if you are cold).

http://cnx.org/content/m42153/latest...ol11406/latest

Quote:
Originally Posted by NeilMyers View Post
True, but what most people are interested in is how many extra calories did I burn on this or that ride. That is what the power meter tells you (indirectly).
No, the power meter tells you how many calories/power you used to move the wheel. It doesn't include the calories/power you produced metabolically for other purposes (including to overcome friction/flexing).

Quote:
Originally Posted by NeilMyers View Post
I don't believe those come into play in this discussion. Yes, those may affect how much of your power is converted into speed, but whether the power was effective or ineffective from a cycling perspective, it is still power you generated and that came from calories you burned.
Metabolism -> power to pedals -> power to wheel (measured typically) -> power to road -> speed.

The technique inefficiencies and the mechanical losses occur before the power to the wheel is measured (those losses of power don't get to the wheel). Just like the metabolic inefficiencies.

Last edited by njkayaker; 10-29-13 at 10:11 AM.
njkayaker is offline   Reply With Quote
Old 10-29-13, 10:02 AM   #19
NeilMyers
Junior Member
 
NeilMyers's Avatar
 
Join Date: Oct 2013
Bikes:
Posts: 21
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Looigi View Post
""Converting watts to Calories

A 1 watt work rate
= 1 joule / second
= 3.6kJ/hour

...

100 watts = 0.864 * 100 / .24 = 358.5 Cals / hr = 1500 kJ /hr
Looigi ...

You lost me on one part. At the top you say 1 watt work rate = 3.6kJ/hour. Later you say 100 watts = 1500 kJ/hour. If the top statement is true, then why wouldn't 100 W be 360kJ/hour? What am I missing? I am sure there is something obvious I am missing here ...
NeilMyers is offline   Reply With Quote
Old 10-29-13, 10:07 AM   #20
NeilMyers
Junior Member
 
NeilMyers's Avatar
 
Join Date: Oct 2013
Bikes:
Posts: 21
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by njkayaker View Post
Metabolism -> power to pedals -> power to wheel (measured typically) -> power to road -> speed.

The technique inefficiencies and the mechanical losses occur before the power to the wheel is measured (those losses of power don't get to the wheel). Just like the metabolic inefficiencies.
Do you see this as being any different for the Garmin Vector, which measures power at the pedals?
NeilMyers is offline   Reply With Quote
Old 10-29-13, 10:13 AM   #21
njkayaker
Senior Member
 
Join Date: Sep 2007
Bikes:
Posts: 9,479
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 61 Post(s)
Quote:
Originally Posted by NeilMyers View Post
Do you see this as being any different for the Garmin Vector, which measures power at the pedals?
I don't see it as very different. But the Vector power > wheel power. Keep in mind that some of the power applied to the pedals is used to move your body weight off of the seat (more or less).

Last edited by njkayaker; 10-29-13 at 10:20 AM.
njkayaker is offline   Reply With Quote
Old 10-29-13, 10:19 AM   #22
NeilMyers
Junior Member
 
NeilMyers's Avatar
 
Join Date: Oct 2013
Bikes:
Posts: 21
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by njkayaker View Post
I don't see it as very different. But the Vector power > wheel power. Keep in mind that some of the power applied to the pedals is used to move your body weight off of the seat.
Interesting discussion. So, a better way to evaluate this is the power measured on your power meter gives you a conservative estimate of the calories you burned. If it says you burned 1,000 calories, then you burned at least 1,000, and perhaps 5-10% more.

For the purposes most people use that information for, I would say that is plenty accurate.

Now if I can figure out how many calories are burned when I walk 18 holes carrying my golf bag. That one is more complex, and the fellows on the golf forums are far less analytical!
NeilMyers is offline   Reply With Quote
Old 10-29-13, 10:22 AM   #23
njkayaker
Senior Member
 
Join Date: Sep 2007
Bikes:
Posts: 9,479
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 61 Post(s)
Quote:
Originally Posted by NeilMyers View Post
Interesting discussion. So, a better way to evaluate this is the power measured on your power meter gives you a conservative estimate of the calories you burned. If it says you burned 1,000 calories, then you burned at least 1,000, and perhaps 5-10% more.

For the purposes most people use that information for, I would say that is plenty accurate.

Now if I can figure out how many calories are burned when I walk 18 holes carrying my golf bag. That one is more complex, and the fellows on the golf forums are far less analytical!
Yes. Yes.

("Calories burned" is one of the less useful purposes of a power meter.)
njkayaker is offline   Reply With Quote
Old 10-29-13, 02:12 PM   #24
Looigi
Senior Member
 
Looigi's Avatar
 
Join Date: Dec 2010
Bikes:
Posts: 8,942
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by NeilMyers View Post
Looigi ...

You lost me on one part. At the top you say 1 watt work rate = 3.6kJ/hour. Later you say 100 watts = 1500 kJ/hour. If the top statement is true, then why wouldn't 100 W be 360kJ/hour? What am I missing? I am sure there is something obvious I am missing here ...
I didn't write it, just cut and paste from the site I cited. Anyway, the author is being loose with his units. In the last equation, it should be

100 "Watts mechanical" = 360 "kJ mechanical"/hr = 358.5 "Cal burned"/hr = "1500 "kJ burned"/hr (due to the .24 metabolic efficiency)
Looigi is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 06:32 AM.