Oh yes, definitely. As you say, not that a 4 month old puppy should be doing anything strenuous anyway.If it's something that's going to end up in a panting, exhausted puppy (which you should really be careful about at that age anyway), I've heard what Trickster heard.
If it's exercise like a stroll around the block exercise, I don't think it matters
You beat me to itTrickster said:It is safe to follow the '5 minute rule' with puppies. I made a long post about exercise in the 'Our Best Advice' thread: