I have a friend (well, aquaintance!), who is also a nincompoop.
I have branded him thus, because he goes to those "spinning" classes in the gym. Strangely, he drives to the gym to do the aforementioned classes and then drives home again.
He tells me that spinning is better than real cycling for fitness and that he could keep up with a real cyclist all day long.
He's the same height as me and I know I can get hold a bike that would fit him; would it be unkind of me to take him out on a non-stop 40 or 50-miler? (i.e. several hours in the saddle, rather than just 30 mins on an exercise bike, which he reckons gets you just as fit as riding up and down bloody big hills for hours)
The trouble is, I don't want to damage him! It takes a fair bit of training to get to the level of being able to ride a fast 50 miler! I have a feeling he may actually collapse en-route (literally).