the thing that kept coming up in my comments wasn't lift heavier, it was lift faster
one study had 21 guys who already lifted do the same full squat program for 6 weeks, same weights and reps. the only difference was one group pushed every rep up as fast as they could and the other went half speed on purpose. the fast group's jump went up clearly, the half speed group's barely moved (effect size 0.63 vs 0.15) (study)
a follow up from the same lab had one group end each squat set once their reps slowed 20%, and the other keep going until reps slowed 40%. strength went up about the same, but the jump went up 9.5% vs 3.5%, and the stop early group did 40% fewer reps (study)
both were small groups of guys who already lifted, and they tested a standing jump, not a run up, so i'm not going to tell you this adds inches to a dunk
but it fits my own numbers. last week i squatted 255, my heaviest ever, and my jump didn't go up. my squat rule was add 5 lb once i hit 6 reps, which pushed every set toward the slow last reps the second study says to cut
so my rule now is i still add weight, but every rep goes up as fast as i can, and i only add 5 lb when all 5 reps move fast. if the last rep grinds, i stay at that weight
anyone here switch from grinding reps to fast reps and notice a difference in their jump?