Back when I started CrossFit at CrossFit King of Prussia, we had an oly lifting seminar with some guest coaches from NY. Although I had previously experience with CrossFit, it was done in a typical school gym where there were only metal plates. Thus, I did not have a ton of experience (let alone good coaching) to refine my olympic lifting. When I started at KoP, my clean and jerk was around 135 and snatch was practically non-existent (not that there's much existence of it today...hm, gotta work on that) Anyway, one of these guest coaches had us box jump and I was wondering, "What the heck does jumping have to do with oly lifting?" Well, it has EVERYTHING to do with oly lifting! You are essentially JUMPING that bar off the ground. Granted, your feet won't much as much as an unloaded jump, but the ability to push through that ground and accelerate the bar is essential. (as is hip extension, etc). Based off my jumping ability, his coach told me he saw my clean and jerk up at 185#; I told him he was nuts. That was summer of 2009. Today, my clean and jerk is 215# and my clean is 225# at a bodyweight of 150# (same as in 2009).
Check out these clips of Pat Mendes for more proof about oly lifters and jumping. This guy is 21 years old (many videos feature him at 20yo) and 285lbs. Incredible. (all videos safe for work)
Unofficial Jr. world record of 207kg snatch. That's 455#!!!!