Here is a link to a study that links increase Hip Dysplasia to lack of exercise from birth to 3 months of age.A number of environmental factors can affect the incidence of hip dysplasia in dogs
Somewhat disputes that fast growth and over feeding are the main environmental factors that contribute to HD.
"ScienceDaily (Mar. 26, 2012) — Hip dysplasia (HD) in dogs is affected to a larger degree than previously believed by the environment in which puppies grow up. It is particularly during the period from birth to three months that various environmental factors appear to influence the development of this disease. During the puppy stage, preventive measures can therefore be recommended with a view to giving dogs disposed to the condition a better quality of life."
"Findings from previous experiments and studies from other countries have indicated that rapid growth and a high body weight are factors that increase the likelihood of developing HD. Randi I. Krontveit's research has shown that rapid growth and high body weight in the first year of the puppies' life did not result in an increased risk of HD. "
"Puppies usually live with their mother at the breeder's for the first eight weeks of their life. Several factors related to the living conditions at the breeder's were shown to have an influence on the incidence of HD. Puppies born in the spring or summer and at breeders who lived on a farm or small holding, had a lower risk of developing HD. After about eight weeks, the puppies began life with their new owner. The opportunity to exercise daily in parks up until the age of three months reduced the risk of HD, whereas the daily use of steps during the same period increased the risk. Overall, it would appear that daily exercise out in gently undulating terrain up until the age of three months gives a good prognosis when it comes to preventing HD."
Just some food for thought.
Provide as much exercise as they would do naturally, or stimulation to do so.
Avoid stairs, or pushing them to hard.