PM4 doesn't give "credit" for all cals burned w/ i

turnere · Post by **turnere** » May 29th, 2007, 12:13 am

It seems this topic must have come up sometime before. Does this bother anyone else?

When you program the PM4 to count down the seconds for interval training, as it keeps its running total of the number of calories burned, it does so only for the active phases and not for the rest periods.

Let's say I'm doing high-intensity interval training, say, 30 sec sprints followed by 60 sec rests, the PM4 only counts the calories burned during the sprints or only one-third of the overall workout.

Taking 1200 cals/hr during a sprint, for a given 30 sec sprint, I'd burn 10 calories.

Then comes the 60 sec "rest" (active recovery, ie. some relatively light rowing at 600 cals/hr, that's 10 calories, too.

(In truth, that's probably an underestimate of the number of calories burned, because the PM4 is making its calculations based on the flywheel movement, not on perceived exertion and heart rate, both of take a while to come down from the anaerobic (or anaerobic threshold) zone.)

But those 10 calories don't get counted in the cumulative tally that the PM4 is keeping.

So when I download my data from the PM4 to Excel, I only get credit for burning about half of the calories burned during that interval training.

I guess I could work around this by doing "just row" and just telling myself when to sprint and when to rest, but then I don't get to have the PM4 count down the seconds and tell me which interval I'm on.

Am I missing something?

If not, is anyone else bothered by this?
(This being the weight loss forum, I thought folks would be interested in getting having an accurate count of their calories burned.)

And if so, should we ask C2 to update their PM4 firmware so that we can have the option of doing it this way? (Or has this been on the wish list for a long time?)

Thanks.

Citroen · Post by **Citroen** » May 29th, 2007, 11:30 am

The PM4 doesn't record any data other than distance rowed during a rest period. So I don't understand what you're asking for.

The way it records calories isn't at all accurate (as has been discussed on here and on http://concept2.co.uk/forum many times), you'll get better data by using a heart rate monitor and watch to capture that metric.

turnere · Post by **turnere** » May 29th, 2007, 11:33 pm

That's my point, that it doesn't capture much of anything happening during the rest period.
Specifically I'd like some measure of the amount of work I've done or calories burnt. It shouldn't be as if nothing is happening during the rest periods, because that's not the case.

I do have a heart rate monitor, the Polar model that C2 sells and that interfaces with the PM4. But here again, data is only recorded for what happens during the sprint periods--what the heart does during the rest periods just seems to vanish. It seems that data shouldn't be ignored.

I notice you say "heart rate monitor and watch. I understand the watches record HR regardless of what the PM4 is up to. Maybe that's what I have to do. OTOH, I do like having the big HR read-out on the PM4 screen.

Seems the optimal solution would be for C2 to count data from the rest periods as well as from the sprints. Should that be so hard to program?

jamesg · Post by **jamesg** » May 30th, 2007, 2:39 am

All you have to do is weigh yourself before and after; the diff in kg x 500 is kCalories produced, as 500 is the latent heat of steam in kCal/kg. Add any water drunk and detract any otherwise lost. This is as accurate as the scales you use, where the resolution is usually 0.1 kg, or 50 kCal +/-. So if you pull for an hour you'll get accuracy around 5%, far better than any other method, a cynic or an engineer might think. Then you can calibrate the other systems or measurements you want to use. There could well be a direct relationship to Wh calculated from monitor data. Unfortunately the monitors seem to give us no measurement of work done, which is quite extraordinary considering the thing's called an ergometer. But it's simple anyway, just multiply time in h by average Watts. Within a week you should have anough data to identify all your constants.

tbartman · Post by **tbartman** » May 30th, 2007, 1:27 pm

This bugs me too, because even though I know that the calories recorded are not entirely accurate, they do give me an accurate measure from one workout to another.

Your options are:

1) Set up a variable interval workout, with each work period and rest period saved as an individual step:

e.g.

Interval 1 - 0:30
Interval 2 - 1:00
Interval 3 - 0:30
etc.

You'll have your data for each step, and you'll obviously know which ones are for you to work and which are rest. The downside is that you can run out of steps (the entire Favorites menu can only hold so many total steps). Also, it is hard to change on the fly (if you want to alter the lengths, you need to re-enter the whole workout).

2) I have been tracking all my data for quite some time, and came up with the following formula by having excel plot a regression to my saved data. Obviously, the PM only really records watts, and generates everything else from there (cals/hr, meters/sec, etc.) C2 may have a simpler equation, but this fits my plotted data very precisely. In your rest pieces, you will still have the downloaded data for time and distance, so you can calculate your pace. If you take your pace (P, in seconds/500 m), and put it into this equation:

(-1*0.00184409*(P^3))+(0.92399271*(P^2))-(159.58587992*P)+10028.96972806

you should get the cals/hr you burned (test this on some of your known data in an excel spreadsheet). Since you now have cal/hr, and you know how long your rest was, you can figure the cals you burned during that rest.

Tom

turnere · Post by **turnere** » May 30th, 2007, 2:08 pm

Good workaround! The problem, as you point out is

The downside is that you can run out of steps (the entire Favorites menu can only hold so many total steps)

Doing such short intervals I imagine you would run out pretty quickly indeed. Maybe if it can hold 6 or so short-long cycles, then take a break, then do "rerow" for the next set.

I appreciate jamesg's pointing out the irony of the word "ergometer".

Anyone on C2 monitoring this?
Can someone spend a half hour or so and tweak the program so we can better "meter" our "erg-ing"?

Thanks.

lowwall · Post by **lowwall** » June 7th, 2007, 1:15 am

I come from a swimming background, where we time our intervals based on a constantly running clock. So I don't even bother setting up intervals in the monitor. Instead, I use the "Just Row" setting and do them on the fly. As long as your intervals aren't too complex, you shouldn't have any trouble. You could even do complex intervals if you want to take the time to write out your workout beforehand.

Of course, you'll lose the ability to capture your exact interval stats, but it might be a fair tradeoff.

Snail Space · Post by **Snail Space** » June 7th, 2007, 3:18 am

tbartman wrote:I have been tracking all my data for quite some time, and came up with the following formula by having excel plot a regression to my saved data. Obviously, the PM only really records watts, and generates everything else from there (cals/hr, meters/sec, etc.) C2 may have a simpler equation, but this fits my plotted data very precisely. In your rest pieces, you will still have the downloaded data for time and distance, so you can calculate your pace. If you take your pace (P, in seconds/500 m), and put it into this equation:

(-1*0.00184409*(P^3))+(0.92399271*(P^2))-(159.58587992*P)+10028.96972806

Great stuff! I've saved the formula so that I can play with it later.

Cheers
Dave