I would say that since your breeder has not had any problems with hip disp.that you should be in the clear.Remember that just like you your dog needs to warm up before any rigours excersize.Go for a fifteen minute walk before you go to the dog park and dog beach...your lucky to have such a thing near you.You cant just plop your dog into the action,the muscles are probably sore. Rub that dog and give some time to rest.All should be well