In article , Are 2 separate 20 minute
aerobic workouts as good as 1 40 minute workout? 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.

It depends.

You could train speed (ie HIIT) and two training sessions would be more
effective for this purpose. But it may be necessary to train endurance
beyond that.

Why does it have to be one or the either? To me doing one or two days
breaking into multi-session daily training is good. Also good to have a
volume day and also to wave load and intensity over a cycle.

So for example you may want to work speed/pace Mondays and Thursday,
moderate intensity on Tuesdays and long, slow distance on Saturday and
then do some cross-training on Wednesday and Friday.