• Exercise-associated weakness is one symptom of polymyopathy.dog image by Michal Tudek from Fotolia.com
  
  Polymyopathy is a blanket term for any inflammatory disorder or an immune disorder that affects the muscles. This type of disorder can be diagnosed through a number of different tests, including tissue biopsies and blood and urine analysis. Though identifying this condition can be difficult, being aware of some of the symptoms can help facilitate diagnosis and treatment.
  
  

Reluctance to Move

• A formerly active dog might gradually become less responsive and less inclined toward activity. Though some dog owners attribute this to age, it may be that the dog feels more pain when he forces his muscles to work, and thus is avoiding it. A dog who is reluctant to move and who has no obvious reason for his reluctance should be brought to a veterinarian.
  
  

Painful Movement

• When your dog moves, is he favoring a certain leg? Does he yelp when he puts too much weight on one leg or moves in a certain way? Some dogs will work through the pain to please their owners, and this can lead to more injury. If your dog is still trying to keep up with you, but is having problems doing so, this may be a sign of a muscular problem.
  
  

Exercise-Associated Weakness

• Some dogs only show signs of weakness after they have been exercising. While they are in action, they look perfectly fine and happy. They are even eager to exercise and to play. However, minutes after they have been active, they might simply lie down and appear weak or exhausted. This is not just normal fatigue. A dog that is unusually tired or listless after what used to be a normal amount of exercise should be watched closely, and if the situation happens more than once, it should be taken to a veterinarian.
  
  

Periods of Healthy Activity

• One of the things that makes this type of disorder difficult to diagnose is the fact that there may be periods where your dog looks and acts just fine. Polymyopathy can be intermittent, and because of that, you might simply think that your dog has gotten over a mild sprain or some other injury. This is why observation of your dog when he looks injured is important. Keep track of when he seems to be in pain and what might cause it.