From: richard@pegasus.com (Richard Foulk)
Subject: Cycling vs. Running
Organization: Pegasus,  Honolulu
Date: Thu, 5 Nov 92 13:54:28 GMT

Here's something from the `Fitness Q & A' column in the March 1990
issue of Bicycling that I thought some might find interesting:

Cycling vs. Running


Q:  I'm a runner who rides several times a week.  I often wonder how
cycling miles compare to running miles.  For instance, in terms of effect,
how does an hour-long 20-mile ride compare to a 10-mile run that takes
the same amount of time?  Is there a way to figure this out?


A:  It's difficult to make a precise comparison, but I've developed a
general formula that comes pretty close.

A major difference between running and cycling is that the energy you
expend during a run rises linearly with your speed.  In cycling, it
rises exponentially.  This is due to wind resistance, which is a major
factor at cycling speeds.  The result is that each mile you run takes
roughly the same amount of energy (about 110 calories for an
average-size adult), regardless of your speed.  But each mile on a
bicycle uses vastly different levels of energy, depending on how fast
you ride.  As you know, maintaining 20 mph takes significantly more
energy than going 18.

In studies, I've determined average values of oxygen consumption by
cyclists.  I've applied these to develop the following table, which you
can use to estimate the caloric equivalence between running and cycling.

Cycling Speed	Calories    Conversion
    (mph)	Per Mile      Divider
---------------------------------------
     10		  26	       4.2
     15		  31	       3.5
     20		  38	       2.9
     25		  47	       2.3
     30		  59	       1.9
---------------------------------------

Riding 20 miles at 10 mph burns 520 calories (20 miles x 26 calories per
mile = 520 calories).  Determine the running equivalent by dividing
the distance (20 miles) by the conversion divider for 10 mph (4.2).
The result is 4.8 miles.  This means that cycling 20 miles at 10 mph
burns as many calories as running 4.8 miles.

If you rode 20 miles at 20 mph, you would divide by the corresponding
number on the table (2.9).  The result is 6.9 miles.  So, in terms of
energy expenditure, riding 20 miles at 20 mph is equivalent to running
6.9 miles.  Both would burn about 760 calories (20 x 38).

These ratios have some important limitations, though.  They're derived
for an average-size adult (154 pounds).  A larger cyclist would divide
by a slightly higher number; a smaller cyclist, by a slightly lower one.
Wind and hills are not accounted for in the table, nor is drafting,
which can reduce your energy expenditure by up to one-third.

Another way to estimate the training effect of cycling versus running is
to check your heart rate.  Bicycling and running at the same heart rate
require about the same amount of energy, as long as climate conditions
are similar.

In fact, a simple way to gauge equivalence is to forget distance and go
by time and heart rate.  An hour of riding at a certain heart rate is
equivalent to an hour of running at the same heart rate.  Of course, the
body can't tolerate running as well as cycling.  Thus, you can easily
log more time on your bicycle than in your running shoes.

				David P. Swain, Ph.D.


-- 
Richard Foulk		richard@pegasus.com
Newsgroups: rec.bicycles.tech