Wattage and calories?

On Dec 2, 6:06 pm, Woland99 wrote:
On Dec 2, 5:45 pm, "Robert Chung"
wrote:

(BTW, there's a minor error on the Kurt Kinetic page: the coeff for mph^3 is
0.19168)

Thanks. You meant 0.019168.
Or else I am God of Watts - doing 740W for an hour ;-)

OK doing it again,
With 0.22 body efficiency and 0.95 gearing efficiency
and correct speed vs. wattage formula for Kurt's Road machine:
P = (5.244820) * S + (0.019168) * S^3
and for 15mph ride over 20 miles - ie. 80mins
one gets 143W ie. 165kCal spent on just moving the trainer
ie. 165/(0.22*0.95) = 790kCal total energy spent by the body.
Yes - 1672kCal given by Garmin is entirely optimistic.

Using GPS2PowerTrack plugin in SportTracks gives 765kCal for
the same ride - much closer figure (that plugin assumes 22%
efficiency...) difference may be assumption about rolling
resistance of the tire.

I think that bottom line is that given the unknown parameters
ie. your body efficiency and (to smaller extent you gearing
efficiency - with rolling resistance of the tire included)
one can only get rough estimate about calories burnt during
any session on a trainer or ride outside.

Woland99 wrote:
I think that bottom line is that given the unknown parameters
ie. your body efficiency and (to smaller extent you gearing
efficiency - with rolling resistance of the tire included)
one can only get rough estimate about calories burnt during
any session on a trainer or ride outside.

Well, I wouldn't have said that was the bottom line. Whether you can get
only a rough estimate is a completely different question than whether it's
worth the trouble. If you were really truly interested in finding out your
efficiency, that's entirely possible. It's also possible to measure rolling
resistance and power, both indoors and out -- the Kurt's power-to-speed
curve appears to be reasonably good, and there are on-bike power meters that
can measure power while on the road.

"Woland99" wrote in message
...
On Dec 2, 6:06 pm, Woland99 wrote:
On Dec 2, 5:45 pm, "Robert Chung"
wrote:

(BTW, there's a minor error on the Kurt Kinetic page: the coeff for
mph^3 is
0.19168)

Thanks. You meant 0.019168.
Or else I am God of Watts - doing 740W for an hour ;-)

OK doing it again,
With 0.22 body efficiency and 0.95 gearing efficiency
and correct speed vs. wattage formula for Kurt's Road machine:
P = (5.244820) * S + (0.019168) * S^3
and for 15mph ride over 20 miles - ie. 80mins
one gets 143W ie. 165kCal spent on just moving the trainer
ie. 165/(0.22*0.95) = 790kCal total energy spent by the body.
Yes - 1672kCal given by Garmin is entirely optimistic.

Using GPS2PowerTrack plugin in SportTracks gives 765kCal for
the same ride - much closer figure (that plugin assumes 22%
efficiency...) difference may be assumption about rolling
resistance of the tire.

Now you are getting numbers close to those I offered you in an earlier
reply -
"My sums give me a figure of around 700 kCal for that trip in terms of the
energy requirement to power the bike plus you could add around 95 kCal
required to power you. Giving just less than 800 in total."

You now also mention the Garmin Edge 305. I have a F301 and it produces
similar answers to your Garmin. It as long been contended on Garmin
newsgroups that Garmin has got its algorithm wrong for calculating kCal. The
most popular view that fits most users experiences is that they have missed
the conversion factor of 2.2 pounds per kilogram in their sums. Your numbers
fit in this ball park i.e. 1672/2.2 =760!!!!! It seems that after years of
complaints from users Garmin still have not addessed the issue and their
calorie figures are still out by coincidently a factor of around 2.2. My
advice is forget Garmin your SportsTracks figure is a much closer
approximation.

If you want to approximate calorie consumption from heart rate then you need
you min and max heart rates plus a knowledge of your VO2 max. Here again you
only get an estimate but it will be a damn site closer than Garmin's

Graham.



I think that bottom line is that given the unknown parameters
ie. your body efficiency and (to smaller extent you gearing
efficiency - with rolling resistance of the tire included)
one can only get rough estimate about calories burnt during
any session on a trainer or ride outside.

On Dec 3, 1:47 am, "graham" wrote:
most popular view that fits most users experiences is that they have missed
the conversion factor of 2.2 pounds per kilogram in their sums. Your numbers
fit in this ball park i.e. 1672/2.2 =760!!!!! It seems that after years of
complaints from users Garmin still have not addessed the issue and their
calorie figures are still out by coincidently a factor of around 2.2. My
advice is forget Garmin your SportsTracks figure is a much closer
approximation.

Nice! so basically I was getting numbers of calories burnt that a
sumo wrestler on a bike would burn. No wonder I felt free to be on
a sumo diet and had such a hard time losing weight!

I will switch to calculating calories from GPS2PowerTrack plugin
and for trainer I may use Kurt's formula + factor 0.22 and 0.95.
Altho GPS2PowerTrack gives reasonable answer in that case - within
10% range and possibly underestimating calories - which is good.

"Woland99" wrote in message
...
On Dec 3, 1:47 am, "graham" wrote:
most popular view that fits most users experiences is that they have
missed
the conversion factor of 2.2 pounds per kilogram in their sums. Your
numbers
fit in this ball park i.e. 1672/2.2 =760!!!!! It seems that after years
of
complaints from users Garmin still have not addessed the issue and their
calorie figures are still out by coincidently a factor of around 2.2. My
advice is forget Garmin your SportsTracks figure is a much closer
approximation.

Nice! so basically I was getting numbers of calories burnt that a
sumo wrestler on a bike would burn. No wonder I felt free to be on
a sumo diet and had such a hard time losing weight!

I will switch to calculating calories from GPS2PowerTrack plugin
and for trainer I may use Kurt's formula + factor 0.22 and 0.95.
Altho GPS2PowerTrack gives reasonable answer in that case - within
10% range and possibly underestimating calories - which is good.

If you are happy with my explanation you can continue to use your Garmin if
that is more convenient just where it says enter your weight in pounds
simply enter the kilogram equivalent and it will agree more closely with
your other estimates. That's what I and many other users have done.

Graham.

"Woland99" wrote in message Nice! so basically I was
getting numbers of calories burnt that a
sumo wrestler on a bike would burn. No wonder I felt free to be on
a sumo diet and had such a hard time losing weight!


Another thing to consider is whether you are doing the same work on your
trainer at 15 mph as you would be doing when actually riding. The amount of
work required to turn your rear wheel at 15 mph could vary greatly depending
on the trainer resistance. You have no wind resistance and are not actually
moving your weight so the amount of work will depend to a large extent on
how much resistance your trainer is generating. If your heart rate is
similiar to what you have when riding outdoors, the work my be similiar
also.

This doesn't affect the calculation comparisons you are trying to do but it
will affect the calories you actually burn and could explain the
difficulties with the sumo diet.