I watch videos like this and I'm wowed for the first 10 seconds, and then my medical background starts nagging me.
"He has absolutely no protection on his arms or lower legs. If he wipes out - that'll be painful at the least. Skin grafts, scrubbing the gravel out of the wounds. Possible fractures. Months in hospital, rehab. If he survives."
"At least he had fun, I guess?"
No medical background, but I instantly went to the same thought process... that and thinking that if the guy in front breaks suddenly they are gone.