PS....
I wrote:
> There is no correlation between "heart rate" per se (or percentage of
> max heart rate) and calories burned.
I still believe that statement to be correct. But some years ago,
apparently I did derive a general formula -- perhaps something similiar
to what an HRM might rely on. I posted the following explanation
(edited).
I have not found an online calculator. But I have derived the
following formulas, based on data gleaned from the web. (See footnote
[1].)
kCal = V02max * (%MHR - 37) * 0.000075 * time
VO2max is in ml/min. Time is in minutes. %MHR is the number of
percent, not a fraction. For example, "50" means 50% or 0.50.
Ideally, estimate your VO2max and MHR using any of the fitness tests
for that purpose [8]. Alternatively (with much less accuracy),
estimate your VO2max and MHR with the following formulas. (Note: The
VO2max formulas are my own, derived from published formulas. See
footnote [4].)
male VO2max = (54 - 0.34*age) * weight
female VO2max = (42 - 0.28*age) * weight
MHR = 220 - age, or any other formula or method
Weight is in kg. Weight{kg} = weight{lb} / 2.2.
Footnote 4 has a gender-independent formula for VO2max. However, it
introduces a 10-20% computational "error".
All formulas are based on statistical regressions, so there is inherent
statistical "error" ("+/- X"). I cannot estimate the standard error
because I do not know the std err for the underlying data. I suspect
that the above is similar to how HRMs compute calories. One HRM vendor
indicates that their estimate is +/- 30-40%(!) [5]. I expect that is
typical.
Example #1:
30-year-old 70-kg male walking 4 MPH at 62% MHR.
(54 - 0.34*30 ml/kg/min) * (70 kg) * (62 - 37 %MHR) *
(0.000075 kCal/ml) * (30 min) = 172 kCal
Example #2:
30-year-old 60-kg female walking 4 MPH at 70% MHR.
(42 - 0.28*30 ml/kg/min) * (60 kg) * (70 - 37 %MHR) *
(0.000075 kCal/ml) * (30 min) = 150 kCal
These example results are similar to results based on the Compendium
[9].
-----
Footnotes
[1] kCal = VO2{ml/min} * kCal/ml * weight{kg} * time{min} [10]
VO2{ml/min} = VO2max{ml/min} * (%V02max / 100)
%V02max = (%MHR - 37) / 0.64 [2]
kCal/ml = 4.8 kCal / 1000 ml [3]
Note that %VO2max and %MHR are the number of percent, not a
fraction. For example, "50" means 50% or 0.50.
[2] Swain (1994)
http://www.brianmac.demon.co.uk/maxhr.htm
[3]
http://courses.washington.edu/conj/vo2_2004.htm
[4] My own formula, based on regression analysis of modified Leger [6]
and ACSM estimate of VO2max for "average" male and female [7]. For age
20-60. For age 60+, compute using 60.
Gender-independent formula:
VO2max{ml/min} = (47 - 0.28*age) * weight{kg}
10-12% error for male; 14-20% error for female.
[5] Posting dated Apr 29, 2004 9:24 AM at
http://forums.runnersworld.com/thread.jspa?threadID=175758&tstart=15
[6] Leger (1982)
http://www.janatrains.com/default.asp?id=19
http://www.brianmac.demon.co.uk/beep.htm
Original Leger, averaged over all ages and both genders, yields a
regression formula similar to Swain, namely:
%V02max = (%MHR - 36) / 0.57
Therefore, I arbitrarily modified Leger to fit the Swain
regression, namely:
%MHR = 45.6 + (0.64 * %VO2max) - 0.41*age + 0.0038*VO2max*age +
1.55*gender
where gender is 1 for male and 2 for female.
[7] ACSM estimate of VO2max, hardcopy, original source unknown.
Provided by the director of a fitness center.
[8]
http://www.brianmac.demon.co.uk/vo2max.htm
[9]
http://prevention.sph.sc.edu/Tools/Compendium_tracking.pdf
[defunct]
http://www.solutionsinfitness.com/kcalexpenditure.htm
http://www.caloriesperhour.com/index_burn.html
[10]
http://www.solutionsinfitness.com/kcalexpenditure.htm >> Stay informed about: Calculating Calories Burned based on Average Heart Rate