Just like humans, dogs need exercise to stay healthy. It goes without saying that not all dogs are as energetic as our Nova Scotia Duck Tolling Retriever friend pictured here. However, the average dog does required 3 hours of mental and physical stimulation per day. Some dogs, like the duck toller, need more than that. Others, like a Chinese Pug, for example, need less. No matter what the breed, though, regular exercise improves muscle tone, joint flexibility, digestion, and cardiovascular fitness. Exercise also helps prevent obesity, which has been linked to numerous health problems in dogs. For an anxious or "hyper" dog, exercise also makes him/her happier, more relaxed and less destructive.

Before beginning a fitness plan, take your pet to your veterinarian for a pre-exercise physical. He or she will check for heart, lung, and joint problems and evaluate your dog's overall condition. Your pal's exercise program should be tailored to his/her age, size, and breed. Ask your veterinarian how much exercise - and what type - is appropriate.

Even if your dog has a health problem, he/she still needs to be fit. Your vet can recommend an appropriate exercise program to work around her condition.

When you exercise your dog outdoors, pick areas with soft grass or dirt. Exercising your pet on hard or slippery surfaces can damage her footpads or lead to falls. If you're one of the many dog lovers discovering agility, notice the surfaces the dogs are expected to jump on. There should always be grass or dirt for outdoor trials and rubber or other matting for indoor trials.

On extremely hot days, exercise can be touchy. Watch closely to see if he/she drinks plenty of fresh water and stop if you notice excessive panting or fatigue.

Also, avoid exercising your pet within an hour of eating, especially if she's one of the larger, deep-chested breeds who are predisposed to bloat. (Bloat is a serious disease in which the stomach fills with air. In serious cases the stomach can twist, trapping the air and causing shock and even death.)

If your dog is pregnant, consider less rigorous activities that don't involve twisting or jumping. Let her set the pace and check in with your veterinarian periodically.

Different breeds require different exercise routines. For the average adult dog, 20 to 45 minutes of moderate exercise, such as brisk walking twice a day, is enough. This guideline applies to most mixed breeds and purebred dogs.

More active dogs, including many of the sporting, herding, and working breeds, may need one to two hours of vigorous exercise each day.

By contrast, small toy breeds may get much of the exercise they need inside an apartment.

Once you've worked up to the exercise level your veterinarian recommends, monitor your dog's activity level. If she still tears through the house or takes flying leaps off your sofa, she might need a more vigorous workout.

On the other hand, take care not to do too much too fast. Remember how you ached after your first aerobics class? Your canine companion can't tell you when she's had enough, so it's your job to look for signs of weariness, including a labored gait or heavy panting.

Over 30 percent of dogs are overweight. An obese dog will be subject to a variety of potential health problems, including reduced fertility and heart conditions that can reduce the life span. If your dog is 15% over average weight then he is too fat. If you do not know your dog's appropriate weight, again, talk to your vet.

If your dog is overweight, you need to check to make sure that you are feeding the proper amount of food. If you are overfeeding, slowly reduce the volume of food to your dog's proper intake level, but be certain that the food that you are providing will satisfy his nutritional requirements.

Encourage your dog to get exercise by playing with him/her. If you think you are doing everything correctly, and your dog is still obese, your veterinarian may need to evaluate your pet for possible medical causes -- such as low metabolic rate, hypothyroidism or diabetes.

Exercise will not only keep your pet looking and feeling great, but it's a great way to strengthen your bond. Have fun!