PM3 calories

[Krysta Coleman]

I think indoor rowing loses some potential popularity because of the calorie issue. I have talked to a couple people who have started using cardio equipment at the gym, mainly for weight loss. I asked them how they enjoyed the erg and both responded that they liked it but the monitor said they were burning less calories per hour (with greater apparant effort) than the other machines, such as eliptical trainer and stairclimber. Maybe the other machines have inflated calorie read-outs? In any case, those are two potential ergers lost. I have to wonder how many other gym neophytes are coming to the same conclusion and missing out on the C2 experience.

- Krysta

[PaulS]

I think indoor rowing loses some potential popularity because of the calorie issue. I have talked to a couple people who have started using cardio equipment at the gym, mainly for weight loss. I asked them how they enjoyed the erg and both responded that they liked it but the monitor said they were burning less calories per hour (with greater apparant effort) than the other machines, such as eliptical trainer and stairclimber. Maybe the other machines have inflated calorie read-outs? In any case, those are two potential ergers lost. I have to wonder how many other gym neophytes are coming to the same conclusion and missing out on the C2 experience.

- Krysta

Indeed a tough dilema when the user themselves says "I know I'm working harder" (on the Erg) but they then take the word of a machine that says "You are burning more calories being comfortable here." (stepper, eliptical, etc...)

Apparently the "Ultimate Machine" would be a TV that reported 5000cal/hr being burnt just for paying attention.

Erging ain't for sissy's!

Maybe say something to them like: "Wow, isn't that amazing that you can burn more calories while hardly working at all?!?!?" <Big Smile>

[seat5]

I mostly use the average pace on the monitor, but sometimes I set it on calories because it's meaningless to me, in other words, I haven't got a certain calorie number matched with a certain pace yet. On some days when my mind is saying "You are too tired to row fast today", if I set it on calories, when I'm done later I usually find I rowed at a faster pace than I thought I was going to be able to that particular session. Strange, but sometimes it helps to not realize how hard you are working. It would probably work as well for me with watts, since I have as little corelation in my mind between watts and pace as I do with calories and pace--and I intend to leave it that way so that this trick will still work when I need it.

A sort of "don't confuse me with the facts, my mind is made up" thing, but it works for me!

[neuro]

This is a long ignored thread, but I thought I would jump in and clarify the issue of calories.

On a rowing machine, calories expended does NOT depend on weight. A calorie is unit of WORK i.e. how much energy did it take to move the flywheel during the time measured. Another measure is the WATT, which is the work per unit time...i.e. how QUICKLY are you expending energy. (1 Calorie is 4170 Joules....1 Watt is 1 Joule per second).

If we assume a frictionless seat, then you don't do ANY work by moving your body back and forth without pulling on the handle. It doesn't matter how much you weigh. Thus ALL the work you do is based solely on how much and how hard you pull on the handle as you row. This information can be expressed in Calories or Joules to represent total work done (or energy expended) or in Watts if you want to know the work done per unit time...but it is pure math, measured by the forces of pulling on the handle, and this is independent of weight. Just like doing one curl...it doesn't matter how much you weigh...pulling a 10 Kg barbell once is fixed unit of energy.

The reason we think we need to take weight into account is because other pieces of equipment in the gym need a weight to estimate calories. The best example is a stair climber. In this case, the work you are doing IS MOVING YOUR OWN BODY. It takes twice as much work for a 50 Kg person to take one step us as compared to a 25Kg person. So the machine needs to know your weight to calculate calories. Estimating calories on a treadmill is a lot more complicated, since weight does play a role, but not as direct a role as with a stair climber. Although once you put the treadmill at any kind of incline, then weight has a dramatic effect.

Summary...the calories as calcuated on the PM monitors are accurate without the weight, since any body weight is moving laterally as opposed to vertically. So it does not affect the measurements. In reality, any friction of the seat will depend on weight, but this will be tiny compared to the work done by the actual rowing.

Neuro (MD, PhD)

[seat5]

I understand that the work the erg is measuring is how fast the flywheel is going, but in reality doesn't it take more umph for a heavy person to move themselves up the slide in order to do the work that it measures? So, it's not really measuring all the work that is actually done. You do have to get your body up the slide in order to do the drive which moves the flywheel. The flywheel would never turn if you didn't do the work of going up the slide--unless you are just rowing arms and back, of course.

...how confused am I?

[Alissa]

This is a long ignored thread, but I thought I would jump in and clarify the issue of calories.

On a rowing machine, calories expended does NOT depend on weight. A calorie is unit of WORK i.e. how much energy did it take to move the flywheel during the time measured. Another measure is the WATT, which is the work per unit time...i.e. how QUICKLY are you expending energy. (1 Calorie is 4170 Joules....1 Watt is 1 Joule per second).

[snip]

Summary...the calories as calcuated on the PM monitors are accurate without the weight, since any body weight is moving laterally as opposed to vertically. So it does not affect the measurements. In reality, any friction of the seat will depend on weight, but this will be tiny compared to the work done by the actual rowing.

Neuro (MD, PhD)

Hi Neuro, Sounds like calories could work this way, if calculated on this basis, however the manual for the PM2 & PM2+ and the on-line use description for those two monitors provides:

A Word About Calories:
Due to the differences in body weight and efficiency, calories on the PM2 are only an approximation of calories burned by the person rowing. The formula used in the PM2 is as follows:

Calories = (4x ave watts/1.639)+ 300 cal/hour x time rowed (in hours)

This formula assumes a person of 175 pounds (80 kg.) and a base rate of 300 cal/hour to move your body through the rowing motion at 30 strokes/minute.

What looks like a different formula is used to calculate "calories" for the PM3 & PM4 and is described on page 6 of their manual:

Formulas Used

Watts = 2.80/(sec/meter)^3
Calories/Hour = Kcal/hr = (watts) x (4) x (0.8604) + 300

Is either of those what you expected? It doesn't sound to me as if the calorie result that's displayed on any of these monitors is the one you describe...

If it is, could you explain a bit more, please?

Alissa

[Shepherd]

Searching for this information today -- odd that it got bumped so recently. Maybe it's a spring fever thing.

I'm trying harder to track my "input/output" of calories in vs. exercise out these days, not with fanatic precision but just to start a good food and exercise diary that I can maintain consistently. Without dropping a few hundred dollars on a Polar watch, I'd just like to know if the PM3 calorie counter is recuperable.

If I weigh 178 pounds and row at 24-26 SPM pulling about 2:00-2:05 on average, can I rely on the PM3 to give me kinda-sorta accuracy? Or are all of its results totally off?

[Citroen]

If I weigh 178 pounds and row at 24-26 SPM pulling about 2:00-2:05 on average, can I rely on the PM3 to give me kinda-sorta accuracy? Or are all of its results totally off?

If I'm female weigh 135 lbs (I'm not) and row @ 24-26 SPM around 2:00-2:05 pace I'll get exactly the same number from the PM3 as you do.

If I weigh 210 lbs (I'm not), same again.

I am ~165lbs, 5'7", 44yrs old - if I row 2:00-2:05pace @24-26SPM I'll get the same calories from the PM3.

It may be a true value for one of the four of us; then again, perhaps not.

Since the number is derived from the watts measured by the PM3 tacho, then the same workout at the same pace, at the same stroke rate, at the same drag factor will give a consistent number of calories.

[neuro]

Hi Alyssa-

Sounds like calories could work this way, if calculated on this basis, however the manual for the PM2 & PM2+ and the on-line use description for those two monitors provides:
Quote:

A Word About Calories:
Due to the differences in body weight and efficiency, calories on the PM2 are only an approximation of calories burned by the person rowing. The formula used in the PM2 is as follows:

Calories = (4x ave watts/1.639)+ 300 cal/hour x time rowed (in hours)

This formula assumes a person of 175 pounds (80 kg.) and a base rate of 300 cal/hour to move your body through the rowing motion at 30 strokes/minute.

It's interesting that this is the formula they use. Let's see if I can break it down. The "+300" part of it is independent of how hard you are working. It's an automatic 300 calories an hour. The manual states that it assumes a 175 pound person moving at 30 strokes per minute. First off, a 175 pound person is going to burn anywhere from 50-100 calories just "SITTING". So I assume that the PM2/3 tacks on an additional 200 calories per hour to move youself around.

What I had said previously about no work being done when weight is moved horizontally on a frictionless surface is correct. BUT, now I realize that although there is no "work" being done (from the standpoint of physics), energy is expended putting a body (yours!) into motion. I.e. giving your body kinetic energy. Energy is again needed to slow down your body and reverse it's direction as you slide back and forth.

So, I stand corrected, there will be some calories burned from sliding back and forth and that will depend on weight (for any physics folks, it's really the MASS...the same energy will be expended if you rowed in space with no gravity). Is 300 calories an hour a lot in comparison to the active work of rowing? I admit that I've never even bothered to see how many calories I've used up during a workout.

As far as the other parts of the formula, yes, this corresponds to what I would expect as the measurement...a conversion from "watts" to calories. 1 watt is .01433 calories/minutes, which is about .86 calories/hour (seen in the manual for the pm3). I can't figure out what the "times four" is all about, or why the formulas you listed between the pm2 and pm3 are different.

But I assume that the only place that weight comes into play is the "300" number, and the other part of the equation is just a direct math conversion from watts to calories/hr. But there is not enough information to know.

I would guess that over the course of an hour's row, 300 calories would not add a significant amount to the workout. But again, I've never even see what the calories come out to, so I'll start paying attention. It would also be interesting to see if the 300 calories/hour include basal metabolic rate (i.e. the 50-100 calories you burn just sitting around) or is 300 in ADDITION to the BMR, due to moving your body back and forth along the rail. They don't say.

I wonder if anyone can provide more information about this?

Neuro

[Shepherd]

Well, I can provide some fuzzy numbers/calorie correlations from memory off the top of my head. If this helps at all.

RowPro (using, I assume, PM3 data) says I burn about 630 calories in a 10K for a 43:00 row, 666 (!) for a 40:00 row.

Half-marathons come out at about 1280; those are about 93-96 minutes on the rower.

5K rows turn out 320 or so, usually about 20:00 on the nosey for these.

I'm at work but have more log info at home. My weight is generally around 178 lbs., 5'9", "decent but not spectacular" physical condition, 34 years old.

[jamesg]

Neuro

300 kCal/h is the supposed amount of heat generated by staying alive, shuttling up and down the slide, lifting your knees, wiggling your ears and everything else that doesn't go into the handle.

4 is our supposed efficiency seen as fuel cells: the chemistry is exothermic and the guess, if that's what it is, is that for every one unit of work we deliver to the handle, we also produce 3 of heat, on top of the 300.

1.639 is an error, it should be 1.163, this is the numerical ratio W/kCal. 0.860 is the inverse of 1.163. 1 kW electric gives you 860 kCal.

[neuro]

300 kCal/h is the supposed amount of heat generated by staying alive, shuttling up and down the slide, lifting your knees, wiggling your ears and everything else that doesn't go into the handle.

4 is our supposed efficiency seen as fuel cells: the chemistry is exothermic and the guess, if that's what it is, is that for every one unit of work we deliver to the handle, we also produce 3 of heat, on top of the 300.

1.639 is an error, it should be 1.163, this is the numerical ratio W/kCal. 0.860 is the inverse of 1.163. 1 kW electric gives you 860 kCal.

Thanks jamesg! Makes sense. I had been eyeing that 1.639 number with distrust.

So the formula makes some sense...it's the energy as measured by the machine the "real" work, but with a multiplication factor for the ineffiencies lost by the body as heat, and an addition for the basal rate of metabolism as you slide.

I have no particular training/experience in exercise physiology. BUT, I have an undergraduate degree in both Electical Engineering and Biomedical engineering, a PhD in the Neurosciences, and an MD. I say that only to point out that I can pick up the basic concepts involved in this discussion fairly well, although I start out from a distant starting point.

So, I've been reading a lot about how to calculate "calories burned" and my oh my is it complicated. Other than weight and gender differences, your calories burned will depend on the TYPE of exercise you do...such as aerobic vs. anaerobic, and whether you are currently burning protein, carbs or fat to get your energy (or actually the ratio of these three). And this depends on both your training history, the type of rowing you are currently doing, and your point in the row (are you just starting the marathon, or just finishing?) Our cells have different efficiencies when they burn protein, muscle or fat.

Also, with better technique you burn LESS calories because you are more effectively transfering power to the handle.

All of these are factors which make it VERY HARD to calculate the actual calories burned. wow, I had supposed it was an estimate, but I hadn't ever thought about how hard it was to calculate/figure a good estimate! There is no "right" answer.

But going back to the original posts in this thread that "because the machine doesn't ask you for weight it's worthless" (paraphrase)...in my opinion the error in measurement due to your deviation of weight from 175 is small compared with the errors in measuring your work, efficiency, etc. And these other errors will apply to ANY device that attempts to give you your calories burned. So the fact that the PM2/3/4 does not ask for your weight does not make it "worse" than a treadmill, exercise bike, or stair climber. Because all of those devices must also use the same various assumptions AND have to factor in a component that is much more dependent on weight than rowing.

I hope that makes sense.

So I would tell folks to use the calories burned as a very rough guide. I think it's useful in letting us know...whoa, that ONE coca cola I had will take me about 20 minutes of rowing to burn off! Bit mostly I think it's just another unit of measure for how hard you worked your butt off...and some prefer to use calories, some prefer watts, and some (like me!) prefer to use the good old fashioned 500m split time!

Neuro