I use them every now and then. They really shock the hell out of your legs. Just leave a bucket by the squat rack cuz they are nausiating as hell. I really get the best growth in my quads when i do high rep squats.
I do high weight low rep squats... then finish my quad work out with 20 rep sets on the leg press. Adding a couple high rep sets to your leg routine definitely helps build size.
Explode on the positive and take 5 seconds to get back to full
stretch and then 15 seconds at the very bottom "one one thousand, two one thousand, three one thousand etc" --15 seconds stretching at the bottom thinking and trying to flex your toes toward your shin--it is absolutely unbearable and you will most likely be shaking and want to give up at about 7 reps. Do this on a hack squat or a leg press
i also like the 20 rep system. i usually do 6-12 reps, then finish with the 20 rep set. i did this with legpress too a few times, drop it down to 4 plates and push out as many as you can, 100 if you can. you get such a HUGE PUMP!!!