I wear all black running shoes on hard ground and 3G (if allowed), no one has ever commented on it. My knees really struggle in mouldies, whereas the extra cushioning of trainers makes a massive difference. I did games a couple of weeks ago that I thought was on grass in the pouring rain so I only took mouldies, it got switched to 3G last minute and consequently my knees were very sore after.Is it just me that would never wear any form of running shoes to referee, just seems unprofessional to me to wear trainers rather than boots