mtalinm

sadly, not at my weight

mtalinm

well I think 50 may have been a low estimate. either that, or I'm massively overestimating how many calories I consume...

my spreadsheet says that my cumulative calorie deficit should have me down 5#, but it's closer to 10-12.

maybe I'm not eating as much as I think I am. or maybe the Garmin unit is more accurate with its calorie estimates than I would like to think. I have my ideal weight instead of actual weight in there b/c the original estimates just seemed way, way off. but I am starting to think they were on track after all!

gbg

You have to be carefull when you weigh in if you are exercising. A lot can be loss in sweat. I went on a few 2-3 hour HOT rides
where I weighed 256 at the start and 247 after. But that is only temporary since once you drink liquids
the weight quickly goes back on. And you can easily fluctuate 2-3lbs in a day.

Usually the start of dieting brings good results that tail off rather quickly, that old last 10lbs is impossible to lose.
Keep keeping track and see if it still looks the same in a few weeks, the more data the better.

mtalinm

I always weight first thing in the morning, and I use a 3-day rolling average to smooth the spikes.

this 10-12# loss came after losing 10 earlier, plus I can feel the shrinkage around the middle (no, not THAT kind of shrinkage), so I'm thinking this is real. but will check in a few weeks from now as you say...

spreadsheet says that I should roughly be doubling my # of calories burned cycling. that's pretty much what Garmin is saying. unexpected...

ljubo

Here's my data from the yesterdays ride:

Distance: 22 miles, mostly flat, some small climbs
Time: 1:45 hours
Average heart rate: 160
Max heart rate: 180

I have a Sigma Heart Rate monitor and I've entered my age (30) and weight (250lbs) so it can calculate my max heart rate an keep me in the ideal fat burning zone (55-70% of maximum HR).

Now, I also had a iPhone Cyclemonitor application which uses built in GPS to measure route and data on the route (speed, climbs, averages...). I also entered my age and weight so it can do the calories spent calculation.

Here's the problem...

GPS which calculated climbs, speed, distance, etc. reported 1700 calories spent

Heart rate monitor reported 2800 calories spent.

Both numbers seem wrong and inaccurate, I would expect that I spent something like 1000 calories. What do you guys think?

Also, how efficient is weight loss at such higher heart rate than the suggested one? Suggested one (60-70% of max) is simply to slow/boring for me.

Thanks.

mtalinm

My rule of thumb is that an automated calorie calculator is usually off by a factor of 2. I would guess that you burn 45calories per mile or so, which would put you closer to 1000 as you said.

What i topically do is enter half my weight into the calculator, and then it comes out right .

gbg

Well your average mph is about 12.6 mph. What kind of bike do you ride (road/MTB)? Is it in the city with a lot of stops and starts.?

Since I ride a MTB with 50psi 2.0" tires in the city with lots of stops and starts I usually avg about 15mph, over 2+ hours.
I think I usually ride at 28kph or about 17.5mph so I tried to do a "no stop" ride as much as I could to see what my average would be.
I still had about 10 or so stops each way (out and back) but over an hour averaged 16.4mph (so with no stops it would be around 17 I assume)
with an average power output of 200watts.
My powertap indicated I burned 690 cals (and I am currently at 264lbs).

All I can say is for me the difference between 12.6 and 16.4 is HUGE. But if you have a lot of stops and starts that
totally kills your avg/speed, 5 mintues of stops over an hour makes a 16mph avg 14.7. (1 red light can be over a minute).

However if my avg speed was 12.6 I would assume I would burn under 400 cals (or 700cals over your 1hr 45m). And I think a Powertap is about
as accurate as you can get, it KNOWS how much work you have done.

ochizon

does it? It still has to make calculations to come up with a number.

gbg

Yes it does. It measures (not calculates) Wattage/Work by some pretty accurate strain gauges. They say within 2% accuracy.
Therefore "IT KNOWS" exactly how much work has been done.


So if 800 Kj of work has been done that equates to about 800 cals burned. As stated earlier in this thread, 800kj = 191 cals.
Tons of research has determined the human body is about 23-25% efficient in producing power (the rest is respiration heat etc).
Therefore the only real CALCULATION is 191X4 (approx) = 770-830 cals depending on how efficient the persons body is.

All these heart rate monitors/Garmins have no idea the work done, that is a total guesstimate, and by the above eg of 1700-2800 cals, a very innacurate one.

mtalinm

agree, Garmin does a crappy job. that's why I cut my weight in half to get something at least somewhat realistic. I've been charting my weight drop over the last several weeks, and it matches pretty closely what I should expect if I were burning that many calories, so I don't think it's far off.

of course a power meter is the best but I think they are $1000+ or so? yikes I'd rather stay married :-)

btw the calorie calculator on ridewithgps looks pretty close to what I get faking my weight on Garmin (i.e., when I use my correct weight). if they can work out some bugs maybe I'll switch to that from Garmin Connect.

Dr. Banzai

22 miles in 105 minutes? That's an average speed of 12.57mph. If I put that into the link below the calories are 474. If you add say %1 grade for some small hills it jumps to 904. Do you know what the total grade of your ride was?

https://bikecalculator.com/wattsUS.html

gbg

I think the grade thing is generally a non issue, unless you start at home and end up 22 miles away with an average of a +1% grade.
If you start at home and end up at home your grade = 0%. Even if it is 5% going out it is -5% coming back.

But the grade thing is huge when you are riding up one. I see 220 watts hit 4-500+ watts at 28kph and it doesn't even look that steep.
I am going to use my polar 400 which has an inlcinometer (sp) to get an idea of what the actual grades are, I would doubt it would be over 2%.

pacificaslim

Just remember that you don't average out the speeds/effort on climb and decent. You have to look at the harmonic mean. This is because although the distance may be the same, you spend so much more time going up than you do going down.

gbg

This is why I think a power meter is the only true way to get cals expended.

What if you had a 20 mph tail wind up the 5% slope and a 20 mph headwind back down, how much does that effect it.
Or a 20mph headwind up and a 20mph tailwind down. There is no way you can
"calculate" the effect, unless you had a pitot tube on the bike that is hooked up to your computer.
You have to somehow link speed to heart rate but it is still really a pure guesstimate, since personal fitness comes into effect as well.
Some 160lb unfit guy can be doing 200bpm when a fit person at 160lb may be not be breaking 140, they are still doing the same amount of work (Work = Force x distance).

It is sort of like saying a guy 6' 210lbs is 30lbs overweight based on BMI, but he has 17" biceps and and a 32 inch waist with a 6 pack.

bosoxmrkn

Is my Garmin off?

On a Charity ride Saturday I averaged 17.5mph over 3 hours on a 53 mile ride. I'm 5'10 220. Garmin put me at almost 4500 calories based on my HR average at 170bpm.

Thats 90cal/mile.

mtalinm

it's off by about 2x. I would say 40-45 calories per mile at your weight. I'm 275# and assume 50 cal/mile.

btw cal/mile is the right way to think about it!

what I would do is put your weight in the Garmin as 120 or 140 and the calories should come out closer to reality