In article , Ron Ritzman wrote:
On Sat, 27 Sep 2003 21:23:04 +0100, "Peter Allen"
wrote:

No, it takes some time for your body to switch over from sugar burning to
fat burning.

And what fuel you are burning during exercise is important why?

If you want to keep going for hours on end it makes a difference.

Agreed, but the OP wants to do "2 separate 20 minute workouts, not
through hike the Appalachian trail.

The problem is that OP does not state training goals. Completing the workouts
is probably the means to some end, not the training goal.

Cheers,
--
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/