Amazing! Thanks for posting it Barbara
and it clearly shows how physically demanding agility and flyball etc. are for our dog's bodies.
When William and I did agility he was usually a clean jumper but as a handler it's almost impossible to see exactly what happens when they fault because it happens so quickly and you're already looking and moving ahead to the next obstacle.
It's easier to see when you're training than it is when you're competing. I suspect that William's disk problems are either due to weaving quickly or putting the brakes on when coming down the A Frame to make the contact. I have some still photos of him coming down A Frames and you can see him bracing his front legs and back with his back legs tucked underneath him.