A puppy may only exercise for a ratio of 5 minutes per month of age twice daily until they are fully grown. If exercised more than that, they will get joint problems.
Well…maybe, maybe not! For small dogs – almost certainly fiction, for large dogs - probably fiction. But there is some truth here. The problem is, no one really knows for certain. There have been some studies looking into this question and some found that dogs that had a familial predisposition of having certain joint diseases anyway (OCD and hip dysplasia) developed smaller problems if they were deliberately exercise restricted (i.e. very very small amounts of exercise). This is probably because the repeated pressure on the joint surfaces exacerbated these problems. Since these diseases typically affect large dogs, it may be prudent to wait until they are fully grown until they have vigorous or forced exercise. In this context, forced exercise just means any time they exercise beyond what they would do if totally left to their own devices – this might be going for a jog with their owner or running with other dogs and getting so excited that the puppy carries on even though it is tired. This pretty much aligns with what most of the veterinary orthopaedic surgeons who I have been able to glean an opinion from say. The specific ratio of 5 mins per month does not seem to be based on proven fact and certainly, if you are going to say the above statement with absolute certainty, it seems that you are not really following the actual evidence. Of course, the problem with restricting exercise is that puppies are bundles of energy and without adequate exercise, they can get very frustrated. Sometimes this can lead to behavioural problems.
So, what do I advise for my patients? - I try to keep it simple – exercise a puppy (of any age and size) as much as they want, but the minute they feel tired, stop. This means that until they are fully grown, it is really important to be super vigilant for any signs of slowing down or reticence to continue when exercising – especially when they are highly excited (e.g. when they are running with other dogs). Also, try to avoid high impact movements – like running down stairs, jumping off high surfaces.