I think we have the same friend. A guy at my workplace is giving commuting a chance and also recently did a 25K charity ride for me. He has an older 10 speed with the seat adjusted at least 4" too low. He's already complaining about sore knees. Go figure. I tried to suggest that he raise the seat a bit so that he only has a slight knee bend in the down stroke of the pedal however his ego won't allow for suggestions. Perhaps his inevitable physiotherapist will have more luck convincing him of proper bike fit.