Exercising puppies must be done very gradually to avoid putting excess strain on their growing bones.
The main growing time of a puppy is from 2 to 10 months of age, it is the most critical time of both its mental and physical development. In a growing puppy especially a giant breed too much exercise as a puppy can cause more problems than too little.
Build up exercise gradually.
Long walks on the lead must be avoided for young puppies as should any activity that involves jumping as damage done at this crucial growing time could develop into conditions such as hip-dysplacia and osteochondritis.
Letting a Pyrenean Puppy go up and downstairs also places strain on the joints so it is sometimes beneficial to place a dog gate at your stairs to prevent this.
When lead training remember to not let your puppy pull otherwise when it is fully grown you will not be able to walk him / her it will be more like they walking you!
Pyreneans are reknown for not being good off the lead however with this said both of mine are excellent off the lead whether its down to training or individual dogs im not sure!