Daily exercise is good for both your kitten's mental and physical well-being. Exercise can help your baby cat avoid problems with his joints later on in life. Basically, getting your cat in the habit of regular physical activity while he's young is the cornerstone to a long healthy life and helps his physical development.
How Much is Enough?
Make sure you're consistent with the amount of exercise your kitten gets. You need to help him build its stamina, and the only way he can do this is by exercising regularly but with caution. At the kitten stage, he's much too young to be doing the rigorous activities that he will be more able to do as he grows older.
The amount of exercise your kitten needs depends on his age, breed and medical condition. Not every breed will be up for a long walk through Central Park. Some breeds are just not built to go the distance, while others are always ready to romp.
But in general
You should try to spend about 10-15 minutes a few times each day engaging your cat in some form of activity. Young cats and kittens will usually take the initiative in engaging you in play, or they will find their own entertainment.
Take a look at : Exercising with Your Cat: A How-To Guide