FWIW, the last time I did use a resistance trainer, I was doing interval/sprint training and really getting up to good "speed" when suddenly the little fan wheel flew off the trainer (fast!) and made a hole in the wall on the other side of the room. It didn't just come loose, the sheet metal literally tore itself off at the edge of the resistance fan. Probably a freak accident and not something likely to happen again, but I mention so as to suggest periodically checking any trainers with metal fans to see if any cracks are developing. I'm just glad the fan went backward and not upward!