Many dogs just love to play fetch, mine included. You may use a 'launcher' like that pictured, enabling you to throw some distance. Your dog seems to be 'having a ball' and is exhausted afterwards. Great hey?
However, this repetitive activity may be causing much more harm than good.
Dog trainer 'Lyndsey Canine Coach' has written an article on the behavioural and physical problems she regularly encounters as a result of repetitive chasing of a ball, and the reasons for this. Click here to view her post. It is definitely worth a read and will certainly make you think twice.