After years of taking slams on my snowboard and skateboard, and 20ish years of sleeping on my stomach, I started making pots. It was the perfect storm of low back issues. For a few years I just dealt with the aches and pains. Four years ago, a particularly bad fall on my snowboard landed me in a chiropractor's office having lost almost all movement of my neck. A few weeks of pretty intense massage+electrostim+adjustment and I was back on snow wth full range of motion in my neck. Phew.
Once my neck issue was triaged and dealt with, my chiropractor suggested we address some of the other spinal issues I'd been living with, primarily low back pain. Music to my ears. My work in clay had grown into a fullblown passion and small business, and simultaneously I'd begun coaching snowboarding... there were many nights where I couldn't stand up straight or walk without intense pain. I was 25 years old and terrified that I was going to have to give up the activities I was best at, and that made me feel the best while doing them.
I recognize this thread is about body positioning at the wheel, so I'll fast forward about two years, to the afternoon my chiropractor came to watch me throw to help better figure out solutions for my improved but ever-nagging low back pain. After about a minute of watching he voiced disbelief over how bad of an ergonomical nightmare making wheelthrown pottery is... or at least can be.
Two more years later I have gone from two chiropractic adjustments monthly, to one or two tuneups annually. I still deal with some low back pain, particularly when I get sloppy, but for the most part I live and play quite comfortably. Here's my list of fixes/preventative measures for taking care of your back while throwing:
1. ELEVATE. Raise your wheel and your seat. I have found that my body likes my wheelhead to be a few inches higher than my seat. In this configuration, I have had to learn to rely more on my hands and arms while centering rather than using leverage from my back, so I tend to throw softer clay than what I had been. Ideally, my stool is just shorter than standing height and my wheel is way up on cinder blocks. This is how I keep my wheel at home. Most often I'm throwing at work where the set up is lower than this (6.5" lift using Pacifica's leg extension kit), but the wheelhead being higher than the seat is the most important part.
2. POSTURE. Sit with your pelvis pulled forward to keep it in line with your spine. Once you hunch, you pelvis shifts back and the the spine is unsupported... like the rim of a plate that's been pulled out too far from the base. If it's hanging way out there in no man's land, it's probably going to warp under stress.
3. ENGAGE YOUR CORE. This one is probably the hardest to keep up with, but treat throwing like an ab workout. Just as you would tighten your core muscles to do a crunch, do this on the wheel. Keep your core muscles engaged the whole time you're seated at the wheel. A little trick to help is to envision touching your belly button to your spine. This will help every aspect of your life, especially getting ready for beach season.
4. PROP THE BACK LEGS OF YOUR STOOL. Put a ware board or two under the back legs of your stool to help make steps 2 & 3 easier. I have a length of 4×4 board that I sank 1" deep holes into for the back legs of my stool to sit in.
5. STRETCH. FREQUENTLY. Before you sit down, stretch out. Take breaks to stand up, stretch out and keep your body loose. Do a cool down stretch.
Take care of your back. You only get one.