Calories burned when Cycling

ric/rstsport

phreak wrote:

What would you suggest as an alternative?

i wouldn't. that's the point. you can still lose weight without knowing your energy expenditure. people have been doing it for ever.

cyco2

Druidor wrote:

This ones bugging me as I am trying to loose some weight and have been using MyFitnessPal to tag my food intake and Endomondo tracker that links with it for exercise.

If you put yourself on a decent diet i.e. cut out excessive sugars, fats and carbs you willn't have to exercise at all.

jezzpalmer

Ric/RSTSport wrote:

in terms of weight management it makes no odds whatsoever where your energy comes from, so long as you expend more energy than you consume. Obviously, if you ride extremely hard then the time you can ride for is limited (fatigue sets in) and thus your total energy expenditure could be low. The best way of losing weight (note i'm not saying it's easy to lose weight) is to simply ride as *hard* as you can in the time that you have available (in other words if you have time to do a 5 hr ride, you need to ride it as hard as you can, but still be able to ride on your next available training day)

Thanks for the replies Ric, & Alex.

AK_jnr

Strava seems quite accurate to me. Or as close as it can get without knowing all the info.

Sorry to hijack the thread but as people have mentioned watts etc, could someone give me a rough guide as to average power on my ride from the weekend? Just a ballpark figure. I know its impossible to accurately know but im just interested.

817 feet of climbing over 30 miles, with only mild wind (7mph) 23.6mph average.

Sorry I forgot to add I weigh 70kg

jezzpalmer

Guessing power is as futile as guessing calories, although far from scientific the Strava power figure is probably as good as you are going to estimate.

ric/rstsport

AK_jnr wrote:

Strava seems quite accurate to me. Or as close as it can get without knowing all the info.

Sorry to hijack the thread but as people have mentioned watts etc, could someone give me a rough guide as to average power on my ride from the weekend? Just a ballpark figure. I know its impossible to accurately know but im just interested.

817 feet of climbing over 30 miles, with only mild wind (7mph) 23.6mph average.

Sorry I forgot to add I weigh 70kg

you can get extremely accurate power answer with www.analyticcycling.com - however GIGO applies. data is accurate to within 1 or 2 W

Ric

jezzpalmer

Ric/RSTSport wrote:

you can get extremely accurate power answer with http://www.analyticcycling.com - however GIGO applies. data is accurate to within 1 or 2 W

Ric

That's interesting.
What kind of rides have you found it accurate over, and are they any tips for reducing GIGO?
How does it account for wind speed?

I've just applied this to a ride I did yesterday (48 miles / 3500ft ), and it's around 8% out compared to power meter data (166W).
http://app.strava.com/activities/73836133

Frontal Area 0.50 m2
Coefficient Wind Drag 0.50 dimensionless
Air Density 1.226 kg/m3
Weight 72.0 kg
Coefficient of Rolling 0.005 dimensionless
Grade 0.013 decimal
Wind Resistance 8.2 kg m/s2
Rolling Resistance 3.5 kg m/s2
Slope Force 9.2 kg m/s2
Cadence 83. rev/min
Crank Length 170. mm
Pedal Speed 1.48 m/s
Average Pedal Force 103.9 kg m/s2
Effective Pedaling Range 70. degree
Effective Pedal Force 267.2 kg m/s2
Speed 7.33 m/s
Power 153.5 watts



I re-did it over a section of the ride, a climb of 870ft over 3.2 miles and that is also out by about 10% (PM average was 191W)

Frontal Area 0.50 m2
Coefficient Wind Drag 0.50 dimensionless
Air Density 1.226 kg/m3
Weight 72.0 kg
Coefficient of Rolling 0.005 dimensionless
Grade 0.052 decimal
Wind Resistance 2.5 kg m/s2
Rolling Resistance 3.5 kg m/s2
Slope Force 36.4 kg m/s2
Cadence 77. rev/min
Crank Length 170. mm
Pedal Speed 1.37 m/s
Average Pedal Force 125.8 kg m/s2
Effective Pedaling Range 70. degree
Effective Pedal Force 323.6 kg m/s2
Speed 4.06 m/s
Power 172.5 watts

I guess there must be some garbage going in; upping the frontal area to 0.6 from 0.5 brings it much closer for the whole ride, but makes little (2w) difference over the climb.
I'd need to somehow measure frontal area, I'm 61kg/173cm so not particularly bulky.

ric/rstsport

it's accurate over all rides. on any terrain. potentially more accurate than your power meter (if you haven't calibrated with known certified masses). Differences are due to either an inaccurate power meter or GIGO.

So, with the above, it's highly likely that frontal area and CWD are completely wrong! The product of these is CdA and 0.25m^2 is likely to be a small to moderately sized rider on a TT bike. It's unlikely your CdA is 0.25m^2 on a road bike unless you're very small.

jezzpalmer

How does it account for wind speed?

Say for example I do two rides along the same one mile stretch on different days with 10mph head wind one day and 10mph tail wind the next. If I maintain the same speed on both days my measured power is going to be different, but this algorithm would say that it's the same both days.

ric/rstsport

i guess you're looking at the static forces page/calculator and not the one that calculates with wind velocity?

jezzpalmer

Ric/RSTSport wrote:

i guess you're looking at the static forces page/calculator and not the one that calculates with wind velocity?

Guess so http://www.analyticcycling.com/ForcesPower_Page.html
Which one do you use?

ric/rstsport

the one that says dynamic forces underneath it!

jezzpalmer

Could you post a link to the one you use, please?

ric/rstsport

i don't use theirs. I use actual power data, or some proprietary software we have (www.aero-coach.com)

jezzpalmer

Oh LOL, that's not much help then.
They don't seem to have one that simply allows you to factor in wind speed; even if it did you'd need a couple of pitot tubes to measure airspeed (head and tail) throughout a ride so the average can then be factored in.

By the time you have all this data, averaged out your altitude and rolling resistance over various surfaces, worked out a CdA for riding on the hoods, drops and standing and worked out how long in each position you were and what the relative wind speed and direction was at the time, the lift/drag generated by frame and wheels at various yaws - you may be getting close to actual power.

Yes theoretically working out power is possible, but probably easier to get a power meter and know for sure.

ric/rstsport

i didn't say it was easy . if you don't have a power meter it's easier to calculate power when there is no wind around.

Alex_Simmons/RST

Wind is a large confounding factor in calculating power from speed, even on climbs where gravity is the dominant opposing force it still has a large effect on the calculation. On flatter ground the speed for a given power is highly variable depending on wind speed and direction.

As Ric says, some models such as analyticcycling.com are accurate models, but the accuracy of the answer depends on the accuracy of all the input variables (GIGO). Wind is an exceptionally difficult thing to measure with necessary precision for an accurate power measurement, even barely noticeable air movement can have a large impact on speed at same power.