Interesting photo. I could not help but notice that the chain seems not to be able to keep up with the rotation of the cranks as it is buckeling at the bottom. Either he is putting a terrific strain on this chain or the rear derailleur spring is shot. This can lead to a very interesting problem if it migrates to the derailleur and locks up the drive train. I have had this happen not because I am such a powerful cyclist but more from having a bad sticky chain. It does wonders for the rear derailleur or frame and/or wheel.
Ray Homiski
Elizabeth, NJ