This pilot study aimed to evaluate the 6-minute walk test (6MWT) and a pedometer as noninvasive measures of ambulatory capacity using Labrador retrievers with centronuclear myopathy (CNM) as a model of generalized neuromuscular disease.
Eight purpose-bred littermates (3 affected, 2 carrier, and 3 unaffected) were tested. The dogs were acclimated to the testing area before the study and were repeatedly tested between 9 to 50 weeks of age. The animals were allowed to walk at their own pace for 6 minutes, and distance and pedometer readings were recorded. As affected dogs aged, they developed progressively more severe paresis and exercise intolerance, cervical ventroflexion, and a persistently kyphotic posture.
One of the normal/carrier dogs was unable to complete the 6MWT, but this was determined to be because of behavior rather than exercise intolerance. Two of 3 affected dogs were unable to complete the test because of severe exercise intolerance. Pedometer readings for affected dogs did not differ from those for unaffected/carrier dogs. This was attributed to affected dogs taking a larger number of short-stride steps but covering less distance than unaffected littermates.
The authors concluded that the 6MWT could differentiate between normal and CNM-affected dogs. However, pedometers did not appear to accurately assess exercise intolerance in CNM-affected dogs.