Up till about 8 months I would keep his exercise to short bouts of about 15 - 20 minutes max. two or three times a day. I mean by this free running/playing, without allowing him to wear himself out, i.e. no throwing balls/frisbees etc constantly, just the occasional throw to keep him amused. Lead walking should be kept to a minimum as well, as this takes far more out of them than free playing.
If he has access to a garden or field, he won't take any harm mooching about, but if he is running himself ragged then he should be restricted.
After about 8 months you can gradually increase the lead walking and free running, and after a year you should be ok to let him walk the legs off you!
Try playing hide the toy or stuff food in a playball for him to exercise his mind as well as his body.