3 questions - CADENCE, CLIMBING & CALORIES

[scotty]

(1) CADENCE - It appears that the iAero, averages cadence for the whole ride. This includes the descents where there is very little if any pedaling. The reason I ask is that while getting acquainted with my iAero unit; I have kept utilizing my Polar S720. The average cadence measured on the Polar is usually at least 10 rpms higher than the iAero, so I assuming the Polar only records rpms when the pedal is spinning. I am aware that when I select a portion of the ride, for example a climb where there is constant pedaling that the iAero will show accurate pedaling since climbing requires constant pedaling. Has there been any thought to modifying the software, to only analyze and average the pedaling only when the cadence sensor is registering > 0 rpms?

(2) CLIMBING Totals - While I know the Polar is not the most accurate for climbing totals, it is usually fairly close to published specs for a climb, usally lower. The iAero seems way high sometimes for the total climbing. Why the discrepancy? For instance, I recent ride had published specs of 8500, the polar unit measured 8300, and the iAero measured 9500. There was probably about a 20-30 degree temperature change in the day, was that part of the problem?

(3) CALORIES - From all measures that I see for calories from other sources, it appears to me that Calories are low. When you use caculators on web pages and in programs like cyclistats, the calorie count is much lower on the iAero, sometimes less than half. Again, even the Polar unit which is usually less than the sources I have talked about, has values usally in excess of at least a third, than the iAero. Why the low calorie count? If I am out doing a 200K ride, I should be burning more than 4700 calories.

[racerfern]

Ah, the three C's

CADENCE:
Garmin used to measure cadence including zeros, then they switched to non zero measuring only. So now I have a 705 that measures non-zero and an iAero that measures all. The iAero uses the cadence number to determine if power is being generated so it would be a challenge for sure.

CLIMBING:
It's funny, I think my iAero shows low climbing totals for shorter rides of under 40 miles and shows high for longer rides. It's always within about 200 ft of my 705 and that one has GPS to help it figure things out.

CALORIES:
I use Cyclistats, it's an excellent program but it can't capture or see the efforts that go into climbs or a headwind. It just averages the numbers. I think the iAero calorie count is right on the money. Using your example a 200k ride at about 15mph average would yield about 4700-4900 calories, with average climbing for 125 miles. Of course there are a dozen variables that will throw that off but in general I think the iBike calculations are very good.

[Velocomp]

Regarding calories: Fernando is right, the iBike is dead-on. It is impossible for software programs to calculate calories accurately; they don't know how hard the wind is blowing (and whether or not it's in your face or at your back), when you're coasting on downhills, when you're backing off a bit from your average power (and for how long), etc. The best they can do is assume you're holding the average value 100% of the time. Of course, that isn't true.

The iBike measures with high precision the amount of work (which is a precisely defined term of physics) it takes to move your bike through the ride. Since there is a well known relationship between work done and the calories burned, you're seeing your real number.

You can buy an SRM for thousands more and you'll find it will give the same number of calories as the iBike, within a few percent. We hear they're working on a new model that will be closer to ours...

[travispape]

(1) CADENCE - It appears that the iAero, averages cadence for the whole ride. This includes the descents where there is very little if any pedaling. The reason I ask is that while getting acquainted with my iAero unit; I have kept utilizing my Polar S720. The average cadence measured on the Polar is usually at least 10 rpms higher than the iAero, so I assuming the Polar only records rpms when the pedal is spinning. I am aware that when I select a portion of the ride, for example a climb where there is constant pedaling that the iAero will show accurate pedaling since climbing requires constant pedaling. Has there been any thought to modifying the software, to only analyze and average the pedaling only when the cadence sensor is registering > 0 rpms?

Note that the iAero FW (and iBike FW) does include zeros in the cadence average; however, the iBike2 average cadence does not include zeros. I think we should change the FW, but that hasn't happened yet. In the mean time, you can get your average cadence after you download the ride.

(2) CLIMBING Totals - While I know the Polar is not the most accurate for climbing totals, it is usually fairly close to published specs for a climb, usally lower. The iAero seems way high sometimes for the total climbing. Why the discrepancy? For instance, I recent ride had published specs of 8500, the polar unit measured 8300, and the iAero measured 9500. There was probably about a 20-30 degree temperature change in the day, was that part of the problem?

I just created a post to answer this frequent question: http://www.ibikeforums.com/viewtopic.php?f=4&t=402

(3) CALORIES - From all measures that I see for calories from other sources, it appears to me that Calories are low. When you use caculators on web pages and in programs like cyclistats, the calorie count is much lower on the iAero, sometimes less than half. Again, even the Polar unit which is usually less than the sources I have talked about, has values usally in excess of at least a third, than the iAero. Why the low calorie count? If I am out doing a 200K ride, I should be burning more than 4700 calories.

I have a Polar S720i also and I've noticed the same thing about it reporting more work than a power meter. Realize that the Polar calculation is very approximate based only on your heartrate data and your body parameters: age, weight, gender, etc. Power meters give much more accurate work numbers, but they still have to make an approximation for your efficiency. I think they all use 25%, so you should expect different power-meter-based measurements of work to agree. Note that riders vary on their efficiency and the efficiency for a given rider depends on other factors such as temperature. The body has to work much harder to keep you cool when you are riding on sunny summer days and that reduces your efficiency.

Travis

[racerfern]

Note that the iAero FW (and iBike FW) does include zeros in the cadence average; however, the iBike2 average cadence does not include zeros. I think we should change the FW, but that hasn't happened yet. In the mean time, you can get your average cadence after you download the ride.

So you're suggesting that on the iBike use zero cadence to restrict watts in non-pedaling situations but display non-zero cadence averages? Perfect. Now to get the firmware to display AVG HR and for sub-trips also.