Normally I can take my dog for long hikes in the mountains where we get to a lake and he'll swim for several hours non-stop - retrieving sticks and still not be worn out.

Lately, I have been doing my training at the park (15 - 20 minutes of heel, down, sit, recall and drive building). Afterwards a play 2 ball.

After about 10 minutes (sometimes less) of 2 ball he is worn out and just wants to lie in the grass. I am worried that he is this easily worn out. He won't stop chasing the ball if I throw it but when he comes back he stops short and lays down.

This worried me a little since some people with working line dogs claim it is impossible to wear them out. When we are playing 2 ball I am throwing the ball with a chuck it about 40 yards or so and my dog is in a full on sprint - amazingly fast actually.

Considering he is doing like 20 or so hard full on sprints (the temp is about mid to upper 70s) - does it make sense that this would wear him out?

He is 16 months and when he had his preliminary X-rays the Vet said they were the best Xrays he had ever seen.

Matt ,40 yard to retrieve and 40 yards back 20 times equals 1600yds 3/4 of a mile roughly at full speed in ten minutes.Yes he should be tired for a little while. I work my girl in the same manner and after a short rest she's pestering me for more playtime.

Well, that's what I was thinking, but hearing some of the stories about crazy drive Mals and working line dogs on here - it got me worried that maybe he had hip problems.

After a rest he is as ready to go as ever though.

Also, you are doing obedience training in addition to the retrieving and the dog is using both his mind and his body, which is more tiring than just straight play or exercise.