I have been working on bikes for a few decades now. Starting with the British 3 speeds that everyone had in the early 60's. I took apart many of my friends bikes and my own and my brother's. I never saw, or think I never saw a bent wheel axle nor a bent crank axle. After all, the difference in weight between a skinny teenager and a bulbous adult is only on order of 1 to 2 at worst. (130 lbs vs. 260 lbs give or take). The difference in power output is probably about the same for all participants in casual cycling too.
This last year I found a bent rear axle and a bent crank axle on another bike. Neither bike looked abused and neither bike was ridden by anyone outside of the above parameters I would imagine. How can we explain a bent axle then? I could understand it on a mountain bike that is ridden so that the rider regularly takes on ten foot drops but both these bikes were lightweights that are ridden on road, not on lunar landscapes or by Evel Keneivel types.
Garth Libre in Miami Fl.