Due to a knee problem I never stand up and pedal.In the past it results in shooting pain down the middle of where my knee cap used to be.Today I tried it again ,I winced in pain ,wait there is no pain. I am standing up and pedaling,Have not been able to do that in years.I looked down and saw I picked up 3 mph going up a hill on my ride.I guess all this riding made my leg stronger.I'll take it.Now lets see how long it lasts.