I've always wondered about that... Perhaps cows have strong bones and all but still, wouldn't you be scared and stressed like hell if someone did that to you? Same thing goes for rodeos; I really dislike them both.
Cattle have really tough hides and thick bones, so it doesn't hurt them when it comes to calf roping or any other rodeo event.

When they buck from bull riding, it is because the rope squeezes them, causing them to buck. Like when we get out blood pressure taken. When the cowboy falls off, the rope falls off with him, releaving the bull from the squeezing.

I like rodeos WAY more than bullfighting!! At least the cattle in the rodeo have a nice life outside the ring,and no serious injury is inflicted in them. If there is, such as a streched ligament, medical care is provided for them.