Just like people, dogs need a proper diet and the right amount of exercise to stay fit and healthy.

But it can be hard for owners to know how much time to spend at the dog park.

ILoveDogs.com said that a good basic guideline is 30 minutes of exercise a day. But owners need to see how that works for each pet, because some dogs will be able to go nuts for much longer than that, while others poop out at 20 minutes.

QualityDogResources.com gives the same guideline, but also notes that dogs bred for working farms such as collies may need two hours a day.

Regardless, the time can be broken up into chunks so that neither owner nor pet gets too tired.

But remember: You can't really judge based on a dog's size, WiseGeek.com notes. The breed, however, can give a clue.

A small Jack Russell, for instance, may need a lot of play time each day, but a huge mastiff could be happy with a 15-minute walk.

You can also vary how much exercise your pooch gets by changing up the activities. PetFit.com says that walking burns twice the number of calories as resting, while jogging or playing fetch burns three times. Swimming, doing agility trials or working with livestock burn six times the calories.

Still, you must be careful about how much exercise a dog gets. VetMedicine.com says that owners need to be careful not to overwork young, excited dogs, as well as keep an eye out for damage to feet from running or playing on hard surfaces.

The site also suggests a complete health exam before starting an exercise program with a dog.

Remember that dogs need a workout for their brains, not just their legs. QualityDogResources.com suggests toys with hidden treats to keep a dog's mind active and engaged.