Along the lines of what MOD is saying...
Works better with 4 days but you can do 3 just as well.
Mon/Thur.-- Barbell Clean & press-20min
Tues/Fri-- OL Squat -20min
I've done this exact program to rehab my weak little legs and shoulders. You will grow and you will get stronger. If you have energy left over, you could do any number of things like pullups, seated press, incline bench, occasional Deads, RDL's. If you like the clean and jerk or snatch you can use them in the warm up while you're fresh. It's so simple but super effective, for at least 2 months in my case.
The why I'll leave up to others, , load before reps, rarely to failure. basics big movements always deliver better than any gymnastical flailing or tabata rope skippage.