Stairmaster calories
Alan Monday-US Operations Program Mgr.
"watts"? I haven't done physics in years, but I believe that there are formulae
that can convert one to the other, along with "ergs", "joules", "horsepower", whatever...
The Stairmaster's computer knows exactly how many energy units it has recieved
because it know the mass of its flywheel, how much electro-magnetic resistance it
has put on the flywheel, the rotational velocity of the flywheel, your weight, and the
duration of the exercise period. That is the number of calories you have burned since
you were the "engine" driving the flywheel.
Calorie - the amount of energy required to raise 1 cc of water 1 degree Centigrade?
right?
> A machine can't possibly calculate the exact calories burned, since that
> number depends on more than just weight. A 200-pound bodybuilder built of
> pure muscle will burn alot more calories than a 200-pound out-of-shape/fat
> person (leaning on the rails?)!
>
> Janice
J Green
>Centigrade?
> right?
the calculation of total calories burned (at least on the LifeStep) has
something to do with the weight entered. The total calories is different
for different weights entered. and if not then why ask to enter a weight?!
my original point was, that even if a 200 pound person usually burns more
calories than a 100 pound person doing the same amount of exercise, there
are even differences in numbers of calories burned by different 200 pound
people.
I don't think the Life-Step figures are accurate, but they do help somewhat
to measure progress.
Janice
Jim Roberts
>>Centigrade?
>> right?
Sorry, wrong. A Calorie is 1000 calories, which you approximately
defined.
--
Jim Roberts rob...@stsci.edu scivax::roberts
Mike Coleman
>Sorry, wrong. A Calorie is 1000 calories, which you approximately defined.
Unless, of course, they're *computer* calories, in which case
1 KCal = 1024 calories.
8-)
--
"I suppose it is possible that the stereotype of the wicked scientist
dissuades some youngsters from entering the profession, but the world today is
so topsy-turvy that perhaps as many are attracted as are repelled by the
prospect of a career of malefaction." --P. B. Medawar
Don Kneller
>the calculation of total calories burned (at least on the LifeStep) has
>something to do with the weight entered. The total calories is different
>for different weights entered. and if not then why ask to enter a weight?!
>my original point was, that even if a 200 pound person usually burns more
>calories than a 100 pound person doing the same amount of exercise, there
>are even differences in numbers of calories burned by different 200 pound
>people.
It is pretty easy to calculate the total amount of work done -- "work"
in the physic's sense of "force times distance." Say you are a 200 lb
person climbing at 80 feet/minute for 20 minutes. The total distance
climbed is 80 * 20 = 1600 feet. The total work is:
200lb * (1kg / 2.2lb) * (9.8 N/kg)
* 1600ft * .3062 m/ft = 4.36e5 Nm
= 436 kJ
since 1C = 4.136kJ, this works out to about 105 Cal.
Personally, I've seen measurements of about 5 times this amount, so
I'm not sure where they are getting their numbers from (perhaps I
have an error in the calculation.)
- don
--
Donald G. Kneller
University of California, San Francisco
J Green
me:
>>my original point was, that even if a 200 pound person usually burns more
>>calories than a 100 pound person doing the same amount of exercise, there
>>are even differences in numbers of calories burned by different 200 pound
>>people.
Don:
>It is pretty easy to calculate the total amount of work done -- "work"
I followed your calculations, thanks! :-)
Isn't it also true that a *muscular* 200 pound person will burn more
calories doing the same workout as a non-muscular/fat 200 pound person?
This seems true after the stuff I've heard about maintaining bodyweights.
Thanks again for the calculations! :-)
Janice
Brian Hjelle
>
>It is pretty easy to calculate the total amount of work done -- "work"
>in the physic's sense of "force times distance."
[calculates energy expended on Stairmaster]
>since 1C = 4.136kJ, this works out to about 105 Cal.
>
>Personally, I've seen measurements of about 5 times this amount, so
>I'm not sure where they are getting their numbers from (perhaps I
>have an error in the calculation.)
That's about right. As a first approximation, the body is about 20%
(or so) efficient in performing a physical task. The rest goes up
as heat expended, as muscular contractions that are not turning
the flywheel (e.g., contracting arm muscles), etc. That is why
machines do not calculate calories simply by considering the work
performed on the machine, and why all kinds of different calculations
are used to correct for the body's inefficiency.
Brian
art wittmann
In article <89...@male.EBay.Sun.COM>, al...@usops.EBay.Sun.COM (Alan Monday-US Operations Program Mgr.) writes:
|> I know I can be corrected if I'm wrong, but isn't "calorie" a unit of energy like
|> "watts"? I haven't done physics in years, but I believe that there are formulae
|> that can convert one to the other, along with "ergs", "joules", "horsepower", whatever...
|>
|> The Stairmaster's computer knows exactly how many energy units it has recieved
|> because it know the mass of its flywheel, how much electro-magnetic resistance it
|> has put on the flywheel, the rotational velocity of the flywheel, your weight, and the
|> duration of the exercise period. That is the number of calories you have burned since
|> you were the "engine" driving the flywheel.
|>
|> Calorie - the amount of energy required to raise 1 cc of water 1 degree Centigrade?
|> right?
As has been pointed out, that's a calorie, we usually speak of Kilocalories.
So, you've go to raise 1000 cc's of water 1 degree C.
Some of your units above are not quite right, watts & horsepower are units
of power, power * time = work.
My observation of the stair master is that it does not really sum up the
amount of work that you're doing by measuring the energy disipated by the
machine as you work. It's sort of strange that they don't do it that way,
as far as I can tell, there is a small electrical generator that turns
while you work. I think that the load that you feel is increased or
decreased by changing the resistance that this generator sees. More
elctrical resistance makes the generator harder to turn.
If this is really the way the machine works, it should be easy to calculate
the work done measuring the volts * amps * time across the load on the
generator. That would give you watts * time, which is work. This can
easily be converted to Kcals burned.
What the machine really does (again, from observation) is take the each
level that you've worked at (as indicated by the red LED panel) and assign
a certain number of calories for that level relative to your weight. You
can easily verify this. Try using the machine in manual mode, and just before
the time runs out at each interval - crank it up to the highest level. You'll
probably find that the machine will claim that you've burned a lot more
Kcals than usual (impress your "imaginary workout buddies" or what ever
Dan calls them, err, us).
Of course the real truth comes in measuring the efficiency of YOUR body.
That's why the usual measures of work done aren't all that relevant. Better
ways of measuring your effort are things like watching your pulse rate
and stuff like that.
Art "Geeze, I'm a dorky engineer type" Wittmann
Matt Mahoney
= 1000 (chemistry) calories
= Energy needed to heat 1 liter (1 Kg) water 1 degree C.
1 joule = 1 watt-second
= 4.184 food calories (Kcal)
1 Kg-meter = 9.8 joules
The two PT-4000 stairmasters that I use measure energy in watts or
Kg-meters based on actual work output. However, they measure calories
burned (food calories, that is) by estimating energy input, and by
assuming that 21% or 30% of food energy is converted to mechanical
energy, depending on when the machine was manufactured. I think that
21% is closer to the true figure, but it varies from person to person.
On either machine, the maximum level is 17 mets, or 6:00 per mile, or
128 floors or 2.48 miles in 15 minutes, or 250 watts, or if you believe
21% efficiency, about 1050 Kcal per hour. I don't know how these figures
vary for other weights (I am 160 lbs).
PS. I don't cheat. I stand up straight and lightly touch the hand rails.
I usually do a 30 minute workout, gradually increasing the pace for the
first 15.
-------------------------------- _\/_
Matt Mahoney, m...@epg.harris.com |(TV)| Drug of the Nation
#include <disclaimer.h> |____|
Brian Hjelle
>I know I can be corrected if I'm wrong, but isn't "calorie" a unit of energy like
>"watts"? I haven't done physics in years, but I believe that there are formulae
>that can convert one to the other, along with "ergs", "joules", "horsepower", whatever...
Calories are units of energy, as are kilocalories (aka "Calories"), which is
what the Stairmaster etc purport to measure. A watt is a unit of power,
i.e., energy over time.
Joules and ergs are energy. I believe horsepower is a unit of power (it is
such an antiquated term, a lot of texts don't even bother with it).
>
>The Stairmaster's computer knows exactly how many energy units it has recieved
>because it know the mass of its flywheel, how much electro-magnetic resistance it
>has put on the flywheel, the rotational velocity of the flywheel, your weight, and the
>duration of the exercise period. That is the number of calories you have burned since
>you were the "engine" driving the flywheel.
>
>
Sure, but most machines use some other formula to calculate calories, that
results in a value much higher than that provided by a calculation of
actual energy invested in turning the flywheel. Otherwise, why would the
machine ask your weight beforehand?
The reason they are programmed that way is because the human body is
so inefficient at using calories that several times more energy is
expended as is actually delivered to the flywheel.
Different manufacturers use vastly different formulas to make this
calculation. Some need to know your weight, some don't; some even
consider your pulse rate in the calculation (DP machines). Some
machines actually consider the speed of the flywheel or pedals,
but some "assume" that you are at the midpoint of the target rate.
For an equivalent workout, most machines tell me I used about 10-15
Calories/minute. This is compatible with what the exercise charts
say I should be using for (say) a bikeride or jog. The Lifestep
tells me I used 32-35 Calories/min. It's a good workout, but this
is way too high.
Brian