Do squats and keep your reps at 20 (or close to 20 with failure). IMO these are way tougher than 8 rep squats and they will make your legs grow like weeds. I do something like this:
135 x 20
225 x 20
315 x 20
405 x failure
I squat in a squat rack and I set the pins low enough so I can go ass to the floor on squats. I have a partner there for my last set and when I get stuck at the botttom I have them help me roll the bar off my shoulders.
If you do something similar to this, you don't need to hit another quad exercise. If you can give 100% effort on another set of squats or any other quad exercise, than you did not bust your balls on your last set of squats.
- Keep good form and controlled reps
- Ass to the floor (none of that 1/2 rep shit)
- I like to wear a belt on the last set, but it is a personal preference