There's some benefits from training twice a day (other than being able to boast about it on Getbig and piss people off)
A typical split for me would be chest on my first, shoulders on my second as I never liked to put them both in the same workout. I always felt when it was time for shoulders I couldn't train them as hard after being done with chest (some would suggesting cycling bodypart so I would start off with shoulders, but I rather be fresh and put all my energy into all my bodyparts)
Another would be to split legs and do quads first then hams second (if I do them both in the same workout my lower back gets pretty beat in time for hams which means I can't train that bodypart as hard as I would like)
I train each body part twice a week, one of the workouts being more sets and fewer reps, the other being fewer sets and higher reps. And I don't go to failure so often, if I did the volume would probably be too much.
I also think there might be a benefit as far as how the body handles the nutrition when you train twice a day. Also twice a day could mean hitting weights one time only to come back in the evening to do cardio. It doesn't have to be all weights.
The actual time spent in the gym is no longer than if I would train once a day. It's just that I break it down in order to be able to put a bigger effort into each time and have more energy to spend. If I would keep on adding exercises and make every time last 1,5-2 hours it would probably be counterproductive.
Whether this is something I can stick with for a longer period (or even if I would want to) I don't know yet, I'm just giving it a try.
