I work 8 to 12 hour shifts walking and standing on concrete and brick constantly.  I developed plantar faciitis, a condition which causes acute heel pain, as well as pain in my knees, hips, and lower back.  I read about the Wavespring technology in Spira shoes, and I was hoping these would alleviate the problem.  Although the shoes felt comfortable when worn initially, ultimately they were unsuccessful in relieving any of my foot pain.  I switched, instead, to Brooks Addiction walking shoes, and they worked beautifully.  After wearing the Brooks Addictions for a few weeks, I again gave the Spiras a try.  By the end of a shift at work, my left knee was very painful, and the heel pain had returned.  I recommend the Brooks Addiction walkers instead of these Spiras.  The Wavespring technology sounds logical and promising, but it doesn't stand up for those who work long periods of time on their feet.