There has been a lot of chatter lately about using exercise balls as chairs. There are many who tout supposed benefits of sitting on the large inflatables all day, instead of a contemporary office chair. Contrarily, there are some concerned voices letting us know why it could be a bad idea. It's quite the fad of late with balls showing up not just in homes, but business offices. There is even an established radio/podcast personality who does all of his broadcasts sitting on an iconic blue ball. Ironically, he also demonstrated a risk on his live broadcast. Despite his peril, I've been interested in trying it out myself.
But I had a different idea. I wondered what I could do that would take up less space. Looking around the house for what I had at my disposal, I found some scraps of wood and decided to try a basic one-legged stool. In the quickest build you can call a build, just nailing two already cut scraps of wood together with three nails, I had my new stool. It was just the right height, small, easy to store away, and not a bad sit. Unfortunately it was too stable -- it didn't accurately enough mimic the experience of the exercise ball. The fixed joint gave me too much lateral stability, and the forward width of just over five inches gave it too much forward stability. Worst of all, it didn't bounce.
After some brainstorming, hardware-store-browsing, and conversations with my brother, I decided to go with a heavy spring to yield the quasi-resistive instability I would expect from an air-filled rubber ball. I headed to Lowe's and was lead to a small assortment of springs including the large swing-hanger-springs (the kind that go inline with the chain to reduce the shock on your porch ceiling when you sit). They seemed fit for the task. A stop back to grab a dowel for my post (1 1/8th inch diameter), and I was out at about $15.
In order to best mimic the roll of a ball-seat, the chair (stool) needs to have a joint at the top and bottom, so I salvaged two scraps of decking from my wood pile, cut a 1.5 inch dowel for each and bound them centered with screws into three pre-drilled holes. Having chosen the dowel width to fit, the springs slipped easily, but snuggly over the dowel stubs on each board. Measuring my underseat (shin) length at eighteen inches, I choose to cut the middle segment at eight inches. This left about three inches of unpenetrated spring on each end when adjusted to a total height of eighteen inches. Adding four screws (one at each joint) to keep the spring from slipping under my weight and it was ready for a sit-test.
As it turns out, Three inches of play in each spring is just too unstable. I cut a new dowel at twelve inches and re-assembled. This was much better: stable enough to stay on, unstable enough to require small effort to balance. I'm sitting on this now. I've been on it a few hours now and am starting to feel something. Whether that's the feeling of core exercise, or the destruction of my spine is yet unknown. I expect a stool like this begs the same precautions of the inflated ball that inspired it.
Oh, and did I mention, it bounces...