I only use rollers for indoor riding. Resistance trainers that clamp to the rear axle and hold the bike on the roller are very popular. Looking at these devices and watching riders while using them, I come away thinking they cannot be good for the rear triangle. I see a good bit of twist and torque racking the rear as the bike is pedaled hard. On an unbridled bike, this is not as present because the bike frame (as a unit) can move a little bit. Not so on the axle-clamped resistance machine. All the stress goes into bending rear triangle members. I've never heard of this being a problem. It just looks tough on the bike to my eyes. Anyone have thoughts, or long-term experience with this kind of training device?