The people who struggle learn the snatch – or really perform any overhead lift – are generally adults. Why? Because they've lost a fundamental movement pattern – overhead reaching – that everyone should have! Barring some developmental disorder, everyone has the ability to get the arms overhead when they are kids, whether it's to reach for the cookie jar or to climb on the jungle gym at the playground.
Think about it: the overwhelming majority of teenagers can learn to Olympic lift in a matter of a few weeks or months. And, it's been discussed time and time again how Eastern European kids would practice Olympic lifting patterns with broomsticks to maintain these crucial movement patterns to prepare for the day when they'd load them up. They understood this very important lesson:
It's much easier to maintain mobility than it is to lose it and try to get it back.
This isn't just because tissues can become fundamentally short and degenerative. And, it's not just because resting posture becomes more aberrant or individuals accumulate more wear and tear. It has a lot to do with the plasticity of the human brain. Just like it's a lot easier to train a puppy than it is to teach an old dog new tricks, it's much easier to shape the neuromuscular patterning of a developing child or teenager than it is to change the more concrete patterns of an adult with poor movement quality – especially when that adult insists on trying to learn the pattern with 65 pounds or more on the barbell (rather than just a broomstick) – and after years of sitting at a computer.
This was one of the revolutionary things about CrossFit. I always worked out in one way or another, but CrossFit punished lack of mobility and rewarded improvements in mobility. Thus, working to regain lost mobility wasn't the stuff you "should" do, it was what I wanted to do in order to get closer to my performance goals (with less pain!). Doing the "right" thing is a whole new deal when it is in the context of better performance, instead of just time spent doing stuff that may or may not change how to your work/play/live. I'm still not all eaten up with doing all the mobility work I could do, but one example that stands out is how much change I can see when I squat. At age 49, I can squat to near full depth, cold. At age 42, I could not squat to parallel, even with a warmup. The implication of this regeneration of natural mobility when doing hard work is significant - better performance, greater injury risk threshold for the knees (and the back!), and the ability to squat and do work without back discomfort for much longer periods of time.