Although the problem has been recognized more in male dogs, either sex can be affected. Dogs with this condition are always normal at rest and are usually described as being extremely fit, prime athletic specimens of their breed. Nervous system, cardiovascular and musculoskeletal examinations are unremarkable as is routine blood analysis at rest and during an episode of collapse. Affected dogs can tolerate mild exercise but 5 to 15 minutes of strenuous exercise induces weakness and then collapse. Weakness starts in the rear limbs but then progresses rapidly to the forelimbs, resulting in agenerally weak, wobbly gait.
Dogs ultimately collapse and are unable to continue exercising.
After 10 to 20 minutes of rest, however, they return to normal. A few affected dogs have died during exercise or while resting after an episode of exercise-induced collapse. Affected dogs are less likely to collapse while swimming than when being exercised on land but ambient temperature does not seem to be a critical factor contributing to collapse. Symptomatic dogs are rarely able to continue training or competition. It seems that if affected dogs are removed from training and not exercised excessively the condition will not progress and they will be fine as pets.