**Great site, use and recommend it all the time. In making
some improvements to a weight loss spreadsheet I built, I was
using the Run/ Walk
calculator to confirm usage of the formula it’s based
on. I found an issue.**

**So the MET’s and the VO2 results is based on simple
formula, totally based on speed. So if speed doubles, those should
double.**

**Try walking 2 mph, NET results – 1.5 MET’s and
5.4 VO2. Right on, 53.6448 meters/min * 0.1= VO2, and VO2/3.5=MET’s.
Now try walking 4 mph, NET results – 3.9 MET’s and
13.6 VO2. Nope, 107.2896 meters/min * 0.1 = 10.7 VO2, and 10.7/3.5=3.1
MET’s. That of course messes up the calorie calculation
too when you take VO2*kg/200*minutes.**

**I figured out the turning point in accuracy in the walk/run
calc. 3.73 is correct. 3.74 is incorrect.**

**Why in the world it would take a nose dive then I can’t
tell. Since the corresponding meters/min also is wrong at that
point, can’t be the metric conversion from MPH.**

**I’m guessing either the ACSM formula changed from
2000 and you’ve applied it to some in-between speeds, even
though I can’t find comment of that on any other sites yet.**

**Or there is a real issue in the formula for some strange
reason? I’ve not looked at running speeds over 8 mph to
see any issue there, but 5-8 seem fine on running.**

I created this calculator
in Oct-Nov 2004, so it took me a bit of time to review the various
steps and formulas I had used and to recall issues involving
its development. Notice in the ACSM’s
Guidelines for Exercise Testing and Prescription the notation
for the ACSM walking formula (page 173 of the most recent 9th
edition). You’ll notice the ACSM formula is most accurate
for speeds at 50-100 m/min. And as I hope you will see, there
is a good reason for that upper range limitation.

The formula used I used to predict energy expenditures beyond
100 m/min was created by Bubb, Martin & Howley (source also
cited on the walk/run
calculator page.

In fact, I invited Dr. Edward T Howley, [incidentally also
a former President of ACSM (2002-2003)] to review the ExRx.net
calculator shortly after I posted it on ExRx.net. We primarily
discussed the contrast between figures one of his textbooks (Fitness
Professionals Handbook) which round figures early in the
algorithm versus how javascript handles rounding. We never discussed
the shift in METs using his formula.

At first glance this, jump in METs may appear to be a disparity
possibly caused by some discrepancy or population variations
from two different studies. However this sudden rise in energy
requirements makes much more sense once you plot out the resulting
data on a graph and think about its implications. In April 2012
did just that, displaying the running
and walking efficiencies of various speeds.

You can see a distinct jump in energy requirements around
the point in which you had identified where faster walking speeds
become less energy efficient instead of more efficient. I hope
that clarifies this distinct shift the energy requirements of
walking and my decision to use an additional formula to estimate
walking energy requirements above 100 m/min.