No effect, as far as I can tell. In fact, I hold one of the records at wii-records.com. I use the board on a carpeted floor, and I also neatly fold a few old towels and lay them on top of the board. My original reason for the towels was to reduce wear and tear on my knees, but I also find that the towels help distribute my weight more evenly. This results in better scores on some events like Rhythm Parade and Advance Step. For fairly obvious reasons, I remove the towels for balance games such as skateboarding and golf.