exercise

Question
I have a four month old labrador how much exercise is too much

Answer
The puppy always needs to be able to quit when it has had enough.  Do not force it to continue if it is ready to quit.  Don't encourage it to run and jump.  They do enough on their own.  

Another thing is not to give it too much or too rich of a diet.  If you are feeding a puppy chow, now is the time to switch to an adult chow.  Keep it lean.  Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx