Calorie counters on PM5 vs Fitbit

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Calorie counters on PM5 vs Fitbit

Postby cflrules » May 17th, 2017, 7:02 pm

Hey guys, I set a few goals for calorie/weight loss and just curious if any of you have use a fitbit when rowing to keep track of calories?

I noticed the PM5 claims that I'm burning approximately 40% more calories for the same amount of rowing that the fitbit is. I would guess (hope) the PM5 is more accurate as it would be calibrated specifically for the rowing technique and movements.

I want to make sure my calorie count is accurate. Any experiences or advice relating to this would be much appreciated!

Thanks
40 years old - 6'0" 205lbs.
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Re: Calorie counters on PM5 vs Fitbit

Postby remisture » May 18th, 2017, 5:34 am

Same goes for my Garmin Forerunner 235. The PM5 says 331 calories for a 15 min piece, while the watch (with ErgIQ app connected to the PM5 + HR strap) says 200. I trust Garmin.

https://connect.garmin.com/modern/activity/1730458255

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Calorie formula used by the erg: http://www.concept2.com/indoor-rowers/t ... calculator
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Re: Calorie counters on PM5 vs Fitbit

Postby jimmy1 » May 18th, 2017, 1:37 pm

cflrules wrote:Hey guys, I set a few goals for calorie/weight loss and just curious if any of you have use a fitbit when rowing to keep track of calories?

I noticed the PM5 claims that I'm burning approximately 40% more calories for the same amount of rowing that the fitbit is. I would guess (hope) the PM5 is more accurate as it would be calibrated specifically for the rowing technique and movements.

I want to make sure my calorie count is accurate. Any experiences or advice relating to this would be much appreciated!

Thanks
What mode are you using for rowing on the fitbit? Don't think they have a rowing specific exercise so.... I'm thinking all the data fitbit has to calculate calories is arm movement and heart rate? And an internal metabolic estimate just for staying alive. (Metabolism is significant and likely not included in the PM5 making the rowing contribution to cal burn even greater than the 40% diff observed by the fitbit.)
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Re: Calorie counters on PM5 vs Fitbit

Postby Ombrax » May 20th, 2017, 9:43 pm

There's more info on how to use the info from the C2 monitors here:

http://www.concept2.com/indoor-rowers/training/calculators/calorie-calculator

Re: base metabolic calories used

Note that if you input a calorie value from the PM of 0 and workout time of 0, the cal / hr for the "true calories / hour burned" will not be zero, because the number given for that value does include your base burn rate for your body, even if you were just sitting there, not actively exercising.
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Re: Calorie counters on PM5 vs Fitbit

Postby edinborogh » May 21st, 2017, 12:30 am

the PM5 assumes that you have a specific hight and weight, and based on that it guesses your caloric burn, which is naturally severely inaccurate.
with fitbiz / germin / polar ( im using Polar M400+heart rate strap ) is far more accurate as you insert your specific stats - your hight, your weight, your resting HR and so on.
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Re: Calorie counters on PM5 vs Fitbit

Postby Citroen » May 21st, 2017, 1:22 am

http://eodg.atm.ox.ac.uk/user/dudhia/ro ... #section11 it's the most inaccurate thing in the Universe after 220-age.

That's not to say that any wearable tech is any better, but it has a better chance as Edinborogh says because it's collected some physiology numbers to aid their wonky maths.
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Re: Calorie counters on PM5 vs Fitbit

Postby Ombrax » May 21st, 2017, 2:58 am

I would think that the erg should know exactly how much work you've done in a given workout (within a reasonable degree of precision).

How many calories you had to use to do that work, well, that's a completely different question, and clearly the hard part of the equation.
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Re: Calorie counters on PM5 vs Fitbit

Postby edinborogh » May 21st, 2017, 11:45 am

Ombrax wrote:I would think that the erg should know exactly how much work you've done in a given workout (within a reasonable degree of precision).

How many calories you had to use to do that work, well, that's a completely different question, and clearly the hard part of the equation.


how much work you do, without knowing your age, hight, weight and such is not enough to calculate
the calories use.
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Re: Calorie counters on PM5 vs Fitbit

Postby Ombrax » May 21st, 2017, 4:32 pm

^^^^ Perhaps I wasn't sufficiently clear, but I was acknowledging that in my response.
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Re: Calorie counters on PM5 vs Fitbit

Postby c2jonw » May 22nd, 2017, 8:32 am

I would think that the erg should know exactly how much work you've done in a given workout (within a reasonable degree of precision).

How many calories you had to use to do that work, well, that's a completely different question, and clearly the hard part of the equation.


Yes, the PM on the erg accurately measures the amount of work done on the flywheel. Calories expended by a person to accomplish this work is an approximation that assumes, among other things, a 175 pound person rowing at 25% efficiency with a base Calorie burn of 300 Calories/hour. We have a weight adjustment formula here: http://www.concept2.com/indoor-rowers/t ... calculator that will get you closer but the reality is that the only way to know a person's real Caloric expenditure is through expired gas analysis. So the Calories on the PM should only be used as a reference, not as the definitive guide to how much ice cream you can eat after a workout.......C2JonW
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Re: Calorie counters on PM5 vs Fitbit

Postby jamesg » May 23rd, 2017, 12:51 am

exactly how much work

Work done is average Watts x Time. So taking 25% efficiency as to C2J, total energy is 4 x W x Time.

1000 Wh is worth about 860 kCal. Or just multiply 4xWxT in your spreadsheet and call it kCal, to take account of slide work as does C2.

Accuracy is probably within 10%, so very good considering the cost of the calculation is zero, and we can always calibrate against the C2 reading or even sweat, where 1kg = 500 kCal.
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Re: Calorie counters on PM5 vs Fitbit

Postby EricP » August 29th, 2017, 6:24 pm

Lacking interest in technical analysis I use a different reasoning to work out my calories burned and how that relates to weight loss. Feel free to point out errors in my thinking.

I use an AppleWatch with a Polar strap and HRM. The AppleWatch has a rowing workout. I've seen video of the gym Apple uses to generate algorithms for calories spent while rowing factoring in age, weight, height, gender. It's quite an impressive setup as you can imagine for a company as wealthy as Apple. The people exercising are Apple employees presumably covering a wide enough range of data points to generate useful algorithm estimates. Employees are fitted with o2 measuring devices and I don't know what else. They have a lot of concept2 machines and a steady flow of employees coming to the gym to workout.

From what I can tell the watch uses its accelerometer to measure both stroke length and acceleration from the catch and factors these in with my age, weight, and gender and the algorithm they've developed for that data set to estimate calories burned. While it all sounds great I only care about the consistency of the calorie reading (I get readings on the watch of active calories and total calories which includes metabolic calories, i.e. those my body would expend even if I was doing nothing other than staying alive). Because in the end my watch calculating the calories I consume in a day is only a an estimation based on averages I take the accuracy with a grain of salt. I hope that its estimation is consistent day to day. I think that's all I need.

I currently set my AppleWatch active daily calorie goal at 750 for the full days active calorie burn. I row for 35 minutes with splits at about 2:31 (I'm 70 years old )with the occasional rest to keep my heart rate in the wished for zone and my watch says I burned about 240 calories. That seems very consistent day to day which makes sense as I am pretty consistent in my stroke length and strokes per minute. Along with my other activities I almost always meet my burn goal.

I don't eat the same thing every day but I eat a fairly consistent diet. One's weight varies from day to day but if I watch my weight trend when I weigh myself over time it's either relatively stable, inching up or inching down. If my weight inches up I have 2 options. I can increase my calorie burn goal and meet it until my weight stabilises or I can keep my burn goal at 750 and eat less esp. those foods I know are calorie rich until my weight stabilises. I don't really believe in dieting, I believe in finding a diet I can live with and stick to it.

So in my opinion you're better off using your Fitbit because it's accuracy is less important than its consistency and using my technique above it will help you figure out how to change your diet to meet your reasonable energy burn goals.
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