At what point do you consider yourself to be mashing? Is it simply the gear ratio you're in versus the incline or is it the inability to sustain a certain rpm in a gear? I think this is naive on my part (and the lack of knee pain so far) but I feel lazy if I'm not mashing at least part of the time. I'm on the bike partially to strengthen my legs and get a workoutand I certainly feel the burn a lot more the more time I spend in a higher gear.