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Amtgard Fitness
[03/29/2011] [Glen]

I have been interested in my caloric usage at Amtgard for some time now. This has led me on a journey of discovery into the world of fitness and body measurement devices. In this two-part series I will share my results. In this article I compare different calorie measuring equipment. In my second article, I will review my caloric usage on both a daily basis and specifically when I go to Amtgard events.

Equipment Used:
Sportline DUO 1010 Heart Rate Monitor, retail $69.99
Bodymedia Bluetooth Enabled Armband, $249.99
Schwinn 101 Upright Exercise Bike, $269.99

This is a heart rate monitor. It has a wristband unit, which is essentially a watch, which allows you to touch the face with one hand to get your current heart rate. (It creates a circuit from watch face, through your hand, up your arm, across your chest, down the watch-bearing arm, and back to the back of the watch which is conductive.) It also comes with a chest band that you can wear on (surprise) your chest, just below your pecs. This puts a sensor on either side of your heart and wirelessly communicates with the watch to continuously monitor your heart rate. The watch allows you to enter your gender, age, height, and weight, and then uses this information, plus your continuous heart rate information, to calculate how many calories you are burning.

This is a pretty basic upright bike. It guesses your calories based on how many times you turn the pedals, how quickly you do so, and how much resistance you are applying. It has a heart rate monitor built into the handlebars.

This device, also known as the Bodybugg, is an arm-band that you wear on your upper arm. It measures skin galvanic response, skin temperature, heat flux, and motion to determine how many calories you are burning. It also does nifty things like track sleep efficiency and connects to my smart phone, but that's outside the scope of this article.

My methodology was pretty simple. At 8pm I turned on an episode of a TV show I haven't seen, got on the bike, set the resistance to 5, and pedaled for an hour straight. I did not drink any water or eat anything during this hour. I ate a light but balanced dinner two hours before: 36 grams protein, 35 grams carbs, 5 grams fat, 330 total calories. My total intake for the day was 119 grams protein, 192 grams carbs, 40 grams fat, 1581 total calories.) I'd basically lazed around the house all day until this point.

I am a fairly fit individual. I bike 25 miles a day twice a week on average, as much as five times a week on a non-busy week. I typically hit the gym for two hours a day, two days a week, with 60-90 minutes devoted to weights and the remaining time spent on the treadmill. My resting heart rate is in the low 60's or high 50's. I am 6'2" and weigh in at 205 pounds.

Heart Rate (via Sportline)
Max: 112 bpm
Average: 82bpm
12:50 below target heart rate
47:10 in the target zone.
Target zone is 95bpm to 124 bpm. (user defined)

Calories Burned:
Schwinn: 927
Sportline: 414
Bodymedia: 286

The results for heart rate are, unsurprisingly, pretty uniform. Whether measured by the hand-grips on the Schwinn, the Sportline chest band, the Sportline watch face, or a third heart monitor I used as an extra data point, the readings were always the same. Heart rate technology is pretty simple and pretty reliable.

The results for calories burned were much more varied than I anticipated. The Schwinn thought I was burning 3.24 times as many calories as the Bodymedia and 2.24 times as many calories as the Sportline. The Sportline thought I was burning 45% of the calories the Schwinn claimed and 1.45 times as many calories as the Bodymedia. The Bodymedia claimed I was only burning 31% of the calories the Schwinn claimed and 69% of the calories the Sportline claimed.

Which one is right? I put the most faith in the Bodymedia. It takes the most reliable data points and the studies I have reviewed claim it is fairly close to the gold standard in calorie measurement: volume of O2 measurement. Sadly I do not have access to such a machine.

The calorie monitors on exercise machines might as well be random guesses. Admittedly, the Schwinn does not even take my weight, age, or height into account and many modern machines do. However, my unscientific observation from more expensive machines at the gym is that they are similarly off.

At only $70, the Sportline is a good fit for a limited budget. If you're trying to manage your weight, make the investment instead of relying on on-board calorie counting on your exercise equipment. The exercise equipment will deceive you to a potentially dangerous (to your weight management) degree. If you have the funds, invest in the Bodymedia arm-band.

Clipped from my daily graph of caloric expenditure and stretched out (hence the blurring), this is the Bodymedia's tracking for the one hour I spent on the bike. Click on the image to view a clear version of it.

Useful Calculations (rhr is resting heart rate):
Max Heart Rate (mhr): 220-age
Fitness Zone: .55mhr to .65mhr
Modified Fitness Zone: .55(mhr-rhr) + rhr to .65(mhr-rhr) + rhr
Aerobic Zone: .65mhr to .75mhr
Modified Aerobic Zone: .65(mhr-rhr) + rhr to .75(mhr-rhr) + rhr
Cardiovascular Performance Zone: .75mhr to .85mhr
Modified Cardiovascular Performance Zone: .75(mhr-rhr) + rhr to .85(mhr-rhr) + rhr

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