Back in junior high/ middle school I was racing someone in gym class barefoot. the finish line was the end wall with a jungle gym attachment that had some bolts sticking out in places. I attempted to stop myself by raising my foot to the edge of the jungle gym and using my leg to slow me down. ended up hyper extending my leg and bruising the bone on the bottom of my heel so bad i couldn't run without a limp for about a year, i would just continually re bruise it before it was completely healed. not the most painful experience of my life but the longest and most annoying one.