June 9, 2008

Garmin 405 - 4323 kcal during the bike ride my a**

This weekend I did a long bike around the lake Nockamixon - it is the race venue for my 2 races this year (the Steelman and EnduraSport Half Iron). It is a great 18.5 mile loop around the lake on rolling hills with two fairly good hills - one pretty steep and one fairly long. So it is a great place to ride and train for the terrain common in PA.

On this ride I took my Suunto T6 to monitor my HR, Polar S625X was strapped on the bike as a power meter and just for fun I threw the Garmin 405 in my pocket to get a GPS record of the ride. All went well and the ride was quite nice. I got it done before the huge heat wave came in. I had to re-fuel quite a bit. I may have made a mistake (again) of not taking salt tablets during the ride. But that is not why I'm writing this - the main reason is that as I use the Garmin 405 more and more I found another two major issues new users may need to worry about. I already wrote about the one issue with the elevation data that is just messed-up even on shorter runs or bike rides. But this weekend dring the ride I came across another issue related to energy consumption on the bike. I switched the 405 to bike mode, but even with that setting the darn thing thought I consumed 4323 kcals during the ride. Well not so - according to the Suunto log it is more like 1550 kcal which sounds more accurate. I'm seriously questioning the method Garmin uses to calculate calories. I like the Polar approach better - no HR = no calories information. Better than bad guess in my opinion. Difference between 4300 and 1500 is just too great to be useful.

Second new issue is related to software - Garmin Connect web site where the ride is reported as aerage speed of 11.5mph. Well the math just does not add up on this one - no matter how you slice it riding 56mi in 2:45 is more close to 20mph than to 11.5. Looks like they took the last lap average speed instead of averaging the speed over the entire distance. I hope they can fix this one quickly. The calory consumption issue shows up in the watch so Garmin you really need to release a fix the elevation data and the estimate of calories for biking. I do not burn 77 kcals per mile on the bike. It may be best not to estimate calories expenditure if there is no HR data provided. But that is just my uneducated opinion.

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8 comments:

Leah said...

Hey, in answer to your question about the Bday challenge... I might try it next year, but I dread the thought of swimming 4 miles! :)

kxux said...

I know the swim is kind of long. But you can split it into two 2 mile swims. Many people do that. That way you can start by noon and finish in the morning next day or just spread it out for the Silver or Bronze challenge.

Jeff said...

I did a marathon over the weekend... a marathon viewing of "Flavor of Love" on VH1.

Hope all is well,
-jeff

SLB said...

The altitude should balance out once you load it into MotionBased; there is a setting you need to turn on but I agree with you on the HRM that is pretty off, although it's consistently pretty off.

Ed said...

Interesting, the Garmin interface is so much more pro. How would you rate the Nike+ package against the Garmin's?

happymoe said...

I used my husband's 305 today, and it (unfortunately) showed me how inaccurate the Nike + ipod setup is. I love it, though. It was on a marked trail, and the Garmin matched the mile markers exactly. Unfortunately this also meant I'm even slower than I feared! How is the 405's interface? the 305 is easy, but huge on my wrist. Thanks!

happymoe said...

Oh, and I entered my run today on SparkPeople.com where I track my food, and it said I burned over 2700 calories on a 12 mile run. I WISH!!! I am not sure where these sites are getting their formulas...you're right, without a heart rate, it's just a wild guess.

kxux said...

Yes, calorie expenditure is not an exact science. Pretty much every single HRM or exercise machine estimates the energy you burn. The more variables the HRM considers the closer it gets to the real calories burned. I find Polar and Suunto very accurate. Garmin really did not do well even with the belt for the biking, but maybe they fixed the software in the watch already. And the least accurate are all kinds of machines and devices that determine your calories burned from your weight and exercise duration. They are quite off, to the extent that they are useless.