Forgot to answer your other questions... I would go with rubber instead of carpet, you can always resell the rubber mat if needed and would be easier to take up when needed (no carpet tack strips). Shouldn't need to worry about getting water on the rubber mat to where as the carpet would soak through. I would probably have the floor finished no matter what as it helps protect the wood. Plus it will be one less thing you have to deal with when and if you ever take the floor up.

Hello all! I am a long time lurker and this is my first post. I have really learned so much on these forums. I have searched for answers to my question but couldn't find anything that addresses this specifically. Our last house had engineered wood floors and we had an elliptical machine on top of a thick mat on the floors. When we moved out, we found that the wood floor under the mat was very damaged - not just discolored but warped and cracked - like water damage. I understand that the slab foundation under the wood sweated because we had the mat on top and it caused the damage. We are now moving into a new house with real wood floors and want to make sure we don't make the same mistake. I have searched online and have found that some exercise mats seem to be marketed for wood floors, but I can't find enough about them to feel like they are really different from what I have. Would a "breathable" mat work? Does anybody know of anything that will be safe for the floors? Thanks!

Best way to protect engineer wood floors from heavy exercise machines

Sure....area rugs with natural backing. In other words you will AVOID anything that contains RUBBER or LATEX or VINYL. A rectangle of carpet that is cut and bound will do the trick. I would NOT expect to get anything "squishy" underneath the treadmill. The "squish" comes from rubber/latex/vinyl. Go with an area rug that has a backing that is safe for vinyl and you will be just fine.