I've been messing around with the weights for around 20 years now. It's crazy to think it's been that long. I've been reading about health and nutrition for probably 25+ years. Supplement catalogues and wellness magazines made up a lot of my bathroom reading as a kid. Too much information, or great insight?
Anyway, I remember seeing a video in the early days of CrossFit with Coach Glassman and Nicole Carroll demonstrating the medicine ball clean. Whether a medicine ball is an effective tool for teaching a clean is not the point, what I remember sticking out from that video was the emphasis on the shrug.
I learned how to power clean in high school and I never remember hearing anything about a shrug. My initial impression was, "That's not right. You don't shrug with a clean." You may physically shrug as an afterthought but it's not a conscious effort. Were my teachers and coaches wrong? Was Glassman right? Was everything else I'd seen and read over the years missing a critical step? As time went on I assimilated into the CrossFit style of teaching cleans and had forgotten that it may be an unnecessary step and queue.
When I began coaching I found the power clean to be the most difficult move for most beginners to grasp. There's all these foreign phrases like "tight midline," "second pull," "fast elbows." I found most people over-thinking the whole process and ending up with a reverse curl. But, if you tell a person whose had very little exposure to barbell lifts to jump the barbell up to your shoulders, they can usually pull off something that looks close to a power clean on the first try. It may not be textbook but if the weight is light they can go through several reps of practice without destroying themselves.
As the weight gets heavy I see a lot of people doing power cleans like the guy in the picture, which just looks painful. If you're just doing a traditional power clean, you can come up onto your toes but the feet shouldn't shift to the side at all.
The prerequisites for learning a power clean are competency in the deadlift, and the establishment of a good front rack position. Ultimately the limiting factor in a beginner is their level of coordination and mobility. If a person doesn't have the flexibility and mobility to get into a front rack position, do they really have any business spending time on the power clean? Or would their time be better spent focusing on mobilizing their lats, scapula, chest, wrists and forearms so that they can achieve a proper rack position, and less likely to injure themselves when they join the main class and mob mentality takes over.
I like to take a minimalist approach to group instruction of movements and then give each person individual queues to correct the most apparent technical flaw I see. Once they correct the biggest offender, I drill down from there. If Johnny has three glaring problems with his power clean, I can't give him three separate things to fix all at once. It will be paralysis by analysis. He'll over-think every single thing he does, and probably reverse curl the bar, rather than turn his brain off and just let the movement happen.
If I take the biggest problem first and have Johnny go really slow as he learns to correct his form, then take the second biggest problem and work my way down from there, Johnny will be a power cleaning machine in no time. Simple is better.