Training & Nutrition - How accurate is this calorie display?

I reciently got a Polar A5 and used it on my last ride. I rode in zone for 2hr 13min (2hr 30min total) with an average HR of 146. Anyways the monitor said I had burned 1819kcal, and I'm wondering if that's a reasonable estimate? It asked for my height, age, and weight. I also checked my HR manually and that matched up to the Polar readings.

I'm 18 years old. 5'9 at 164lbs.

That sounds very high. From a common sense viewpoint, I'm not sure that heartrate can be a good measure of calorie consumption. The larger and stronger your heart, the more blood it will pump for every beat, and the fewer beats it will need for your body to do a given amount of muscular work. It's this "work" that determines how many calories you burn, not the perceived effort of doing it. A pro tootling along at 23mph will burn off more calories than a newbie of the same age struggling to keep up 18mph, even though the pro will be making less perceived effort and his heartrate will be much lower.

I think ...

I reciently got a Polar A5 and used it on my last ride. I rode in zone for 2hr 13min (2hr 30min total) with an average HR of 146. Anyways the monitor said I had burned 1819kcal, and I'm wondering if that's a reasonable estimate? It asked for my height, age, and weight. I also checked my HR manually and that matched up to the Polar readings.

I'm 18 years old. 5'9 at 164lbs.
that sounds kinda high especially with a heart rate that low. Maybe it's just me but when I'm on my hardest level of riding my heart rate is at about 170-175. Maybe your resting heart rate is just that much lower than mine but even if you were struggling to get through for that entire time period, over 1800 calories burned still sounds kinda high. That would be around 900 calories per hour! How much of the ride was up hill and what was your average speed?

That does sound a little high, unless of course you're in really good shape, with a low heart rate. A general rule of thumb, is what I use for me.

I figured out, that riding about 18mph, at my weight 173#, I generally burn about 1000 calories per hour. So, if you had your avg speed up to that level and your weight being slightly less to mine, then I would agree, that reading would be fairly accurate then.

I reciently got a Polar A5 and used it on my last ride. I rode in zone for 2hr 13min (2hr 30min total) with an average HR of 146. Anyways the monitor said I had burned 1819kcal, and I'm wondering if that's a reasonable estimate? It asked for my height, age, and weight. I also checked my HR manually and that matched up to the Polar readings.

I'm 18 years old. 5'9 at 164lbs.You may want to compare your findings against this web site...

http://www.primusweb.com/cgi-bin/fpc/actcalc.pl

I'm not voucing for the accuracy of this site but it may give you some insight as to how your calorie function is working. Both methods are very rough estimates.

That is a good rough estimate calculator. I put in my weight, 173#, and 60 minutes of duration.

The cycling 16-19mph came out to about 996 calories, which is about right for me.

One thing you also need to remember, is that I think you should also add the weight of your bicycle if you want it to be more accurate, since you are dragging along 16-20# of road bike, or 30-35# of MTB along with you, and the weight of the bike can vary greatly.

i've compared what my polar tells me to online calculators and they are always in the same ballpark, usually pretty close, which is impressive since the polar is trying to measure calories in such an indirect manner.

Haha well actually my resting heart rate is sorta high to begin with and there are no mountains in my area. I was riding near the beach the entire time.

Bicycling: 12-13.9 mph 1417
Bicycling: 14-15.9 mph 1771
Bicycling: 16-19 mph 2125

That's for my weight and a 135 min duration.

Although my travel computer wasn't working for most of the trip, I think I averaged around 13-14mph. Another thing that could have thrown it off is that I kept the measurements going while taking a quick break halfway in.

1000 kcal/hr requires a power output of around 267W. On flat ground, that's about a 23-24 mph average w/o any aero' equipment.

Don't use a HRM or a chart to estimate calorie expenditure. The result is almost always way too high. Use a powermeter.

1000 kcal/hr requires a power output of around 267W. On flat ground, that's about a 23-24 mph average w/o any aero' equipment.

Don't use a HRM or a chart to estimate calorie expenditure. The result is almost always way too high. Use a powermeter.
you mean something that measures watts right? But I was on this stationary the other day and it was all screwed up. As I increased resistance, for some reason my speed would go up as well. Even when I stayed at a constant speed and Wattage. Maybe the bike was broken or something.

There really aren't any stationary bikes of the type that you would find in gyms that accurately measure power or work. Even the ones used in labs for research can have problems. Trainers with "power" also have problems. Most of the aforementioned don't actually measure power but back-calculate it from speed and resistance which introduces a lot of variables.

...you are dragging along 16-20# of road bike, or 30-35# of MTB along with you, and the weight of the bike can vary greatly.My weight varies greatly; my bike's almost never changes. :)

I don't have access to any power equipment but I found this online wattage calculator ... http://www.kreuzotter.de/english/espeed.htm ... and filled in the information for my particulars. It had me at 243 watts to obtain 17.0 MPH. I don't know how accurate this calculator is though. The calorie function had me at 836 total for 1 hour at that speed. My Polar A5 would have had me at about 1200.

At 267 watts and zero wind it estimated my speed at 19.5 given my stats.

Rider's Height: 68.5 inches
Rider's Weight: 235 lbs
Bicycle Weight: 23 lbs
Air Temperature: 69 F
Height above SeaLevel: 840 (Indianapolis
Slope of Road %: zero (did a loop)
Wind Speed: 3 MPH (it was more windy than that but I was doing a loop so I'm estimating crosswinds)
Pedaling Cadence /min: 80