In article , wrote:

I know that these things can get quite complex but "all things being
equal"

Are 2 separate 20 minute aerobic workouts daily as good as 1 40 minute
aerobic workout daily ?

Any comments will be appreciated.

The biggest disadvantage of two short workouts is that you have twice the
per-workout overhead: more time to prepare for the workout, more laundry, you
will also need to shower after each workout. So it's less convenient.

As far as effectiveness is concerned, the amount of volume is important, but
for endurance work, it may also be useful to incorporate longer efforts into
your schedule (though not every day). Running coaches usually recommend doing
one or two "long runs" (1-2 hrs)per week, and breaking the rest of the milage
into shorter runs.

Having said all that, 20 minutes is actually a very short workout, and 40
minutes is moderate but not long. (I'd call anything over 1 hr moderately
long and anything over 90min long.)

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