We all know how effective 20-rep squat layouts can be at times in our training.
Here . . .
Start relatively easy, three times a week, with something like this . . .
Squat - 1 x 20
DB Pullovers - 1 x 20 immediately after squats, while winded.
Barbell or DB Bench Press - 3 x 6-8
Chins - 2 x as many as possible
Bentover Barbell Row - 2 x 8-10
Seated of Standing DB Press - 2 x 6-8
Barbell or DB Curl - 2 x 6-8
Calf Raise - 2 x 15-20
Situps - 1 x 25-30.
Work your way up to using a squat poundage that will force you to take several deep breaths between each rep, rest pause style, allowing you to get 20 reps with a weight you can be proud of over time. Be gradual, or burn out quickly.
When that gets to be too much for you to recuperate from, go to twice a week, all the while building up those poundages, especially the squat.
Now, when twice a week of that gets to be too much, go to this . . .
Squat - 1 x 20
DB Pullover - 1 x 20 immediately after puff and panting your way through the squats for 20 with much, much more weight than you started with.
Bench Press or Dips - 2 x 6-8
Barbell Row or Chins - 2 x 6-8.
Eat lots. Lots more than you have been eating. Make some kind of heavy duty weight gain shake and sip on it throughout the day, still eating 3 to 6 good sized meals and snacks. In the same way you progressively add weight to the squat bar, add food to your meals, bit by bit, bite by bite.
You will get bigger.
Enjoy Your Lifting!