I got the following e-mail ("e-zine" that I'm subscribed to) which shows some interesting conversion factors to compare cycling to running. If anyone's interested in how to determine how much cycling is equal to a certain amount of running, here's one way to estimate.

(Taken from subscribed e-zine from Dr. Gabe Mirkin)

Dr. Gabe Mirkin's E-Zine
February 29, 2004
Note: No E-Zine next week. The next issue will be 3/13/04

Comparing Cycling With Running

Which burns more calories, running or cycling?. The
standard comparison is that one mile of running equals four miles
of cycling, but that's lousy science. Although running requires the
same amount of energy per mile at any speed (110 calories per
mile), riding is affected by wind resistance so the faster you ride,
the more energy you use. So you have to compare running and
cycling at different cycling speeds.
Dr. Edward Coyle of The University of Texas in Austin
determined average values of oxygen consumption by cyclists to
develop a table to estimate the approximate caloric equivalence
between running and cycling. He found that if you ride 20 miles
at 15 mph, you burn 620 calories (20 miles X 31 calories per mile
= 620 calories). Take the 620 calories and divide them by 110
calories per mile for running and you get 5.63 miles to burn the
same number of calories. So riding a bicycle 20 miles at 15 miles
per hour is equal to running 5.6 miles at any speed.
Dr. Coyle made the calculations easy by providing
conversion factors for different riding speeds: 10MPH=4.2,
15MPH=3.5, 20MPH=2.9, 25MPH=2.3, and 30MPH=1.9. Divide
the number of miles ridden by the conversion factor for your
riding speed to tell you the equivalent miles of running at any
speed. Thus, for 20 miles ridden at 10MPH, divide 20 miles by
4.2 which tells you that your ride is equivalent to 4.8 miles of
running. This formula is for an average-size adult (approximately
155 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 (riding behind
another cyclist), which can reduce your energy expenditure by up
to one-third.

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So this clown thinks that sprinting a mile uses the same amount of energy as jogging it?

Wind and hills aren't accounted for? Yeah, that's just like my ride, perfectly flat and windless

Here's my formula: too many factors + no accurate method of measurement + faulty assumtions = pointless exercise: don't worry about it.