Reply To: Twice-daily training for hypertrophy and strength
The set volume is going to be dependent on the individual's work capacity, so it's impossible to give a specific number of sets. I will say this about twice per day training ------ err on the side of too little rather than too much, and make sure to de-load every third week with once-per-day training that week!
As a general rule, you want higher CNS stress in the A.M. session and more metabolic stress in the P.M. Session. This is on a continuum, so here are two examples for quadriceps:
For maximal strength :
A. Back Squats - 10x1-3 @ 30X0 / 4 min rest
A. Front Squats - 5x3-5 @ 40X0 / 4 min rest
A. Back Squats - 4x6-8 @ 40X0 / 4 min rest
B. Front Barbell Split Squats - 3x8-10 @ 31X0 / 3 min rest
A. Leg Press - 4x8-10 @ 4020 / 90 sec rest
B. Heels Elevated DB Squat - 3x15-20 @ 3020 / 60 sec rest
C. Leg Extension - 3x20-25 @ 2011 / 60 sec rest
As you can see, intensity is relative based on what strength quality you are trying to target. Many tools you can use with these as well, eccentrics, tri-sets, 1 and 1/4, rest-pause, giant sets, etc. Just make sure to make each set count and don't load in a bunch of volume just for the sake of volume. Done properly, this is VERY taxing and best reserved for advanced trainees, and for a small part of the annual plan. Don't blow your wad on twice per day training if you still have a lot of experience to gain and can milk less intense methods for a longer time.
Hope that helps.