Judo Subfloor Analysis

Training over the past month we have noticed that our new judo-style subfloor has been working really well. Big falls do not feel so jarring, and after landing we have been getting a pretty good bounce. This got me thinking…

some Context

My training partners and I are used to training on 2" thick wrestling pads over of concrete. The pads definitely help, but when designing the new academy I wanted to invest a little extra expense and effort into building a judo-style subfloor. Shout out to Chris at Wisconsin Foam Products (chris@wifoam.com) for providing design documents, materials, and shipping at a great price!

The mat was built by putting an array of 3” foam cubes onto the concrete first, and then two layers of 1/2” plywood. This creates a subfloor with springboard feel. Then we laid out 1.5” foam on top of the plywood (instead of 2” wrestling pads) for a sightly stiffer feel to the mats. Add a custom vinyl cover (provided by Bob Henderson at polyfabrics.com) and voilà!

Analysis

Back to the big bounce we were observing after taking a fall. I decided to do a quick analysis of the amount of energy stored in the subfloor when taking a big fall. When the energy from a falling body hits the mats, the subfloor provides a partially elastic collision by momentarily bending out of shape. When the subfloor quickly returns to normal, that stored energy goes back to the body and we can use the height of the bounce to estimate approximately how much energy was absorbed by the mats.

I made a video to explain. Enjoy.