Re: Shoes for practise (on tatami mats)
To John's excellent reply I add:
1. an alternative, if you have patience and time and someone to teach proper taping technique, is to athletic tape the foot as done for active plantar fasciitis, then wear toe sox or tabi - this will avoid the marking problem and the gripping/catching on mat problem
2. never say never. In about 1982 I was taped that way for several months, both feet at same time, then given custom orthotics, told I'd never walk without an orthotic again, etc.....long story short, I did self-graduate to OTC orthotics after a few years, started testing myself in less supportive shoes without those for short periods of time after a few years....when I started training in aikido in 1996 I was able to go barefoot with no problem. I have worn "minimalist" shoes including Vibram 5 fingers and Soft Stars for over four years now, only sometimes reverting to an unstructured shoe (like slip in sneaker) with OTC orthotic. Not saying everybody will have the same outcome. Only that health professionals tend to take a static view of peoples' conditions (and yes I am a h.p. so know this tendency intimately) and ignore that things change over the years. Having proper bodywork done, improving one's structure through budo, etc can very much change the need for external splinting or support.