Restricted Activity, Exercise, and Thermoregulation in Dogs
Used with permission from  Allsorts' Dog Pictures		Photographed by Robin  and Harold Winter. Used with permission from Narnia Kennels.

Effects of Bed Rest on Humans

In humans prolonged bed rest causes a headward redistribution of fluids, vascular fluid-electrolyte shifts, decreases in vascular and total body water, reduction of muscle mass, increased fat content, negative balances of calcium and nitrogen, and changes in glucose tolerance.  Diminished work capacity and increased rectal and esophageal temperatures are seen in bed-rested humans during exercise.

Restricted Activity in Dogs

Restricted activity in dogs has an effect on their thermal and metabolic responses to exercise.  Confinement for eight weeks to cages limiting activity to standing, laying down, and slight forward and backward movement had the following effects on dogs:

• Decreased exercise endurance
• Higher rates of increase in rectal temperature during exercise
• Decreased levels of muscle glycogen during rest
• Increased mean blood hemoglobin concentration at rest
• Decreased adipose sensitivity to the lipolytic action of catecholamines

Exercise training in dogs can have an effect on their physiological responses to exercise.  After eight weeks of confinement an eight week training program consisting of an hour of exercise a day, six days a week had the following effects on dogs:

• Increased exercise endurance
• Increased resting muscle glycogen levels
• Lower muscle glycogen levels at exhaustion
• Restoration of lower rates of rectal temperature increase during exercise
• Increased adipose tissue sensitivity to the lipolytic action of catecholamines

Dogs appear to become exhausted during exercise when their rectal temperatures reach a certain level.  This suggests that hyperthermia due to exercise may be a major limiting factor of exercise performance in dogs.  In one study dogs were able to exercise for the longest amount of time before exhaustion and use the highest amount of  available muscle glycogen during exercise after eight weeks of exercise training.  The dogs exercised for the least amount of time before exhaustion and used the least amount of  available muscle glycogen during exercise after eight weeks of restricted activity.  A possible cause of the decreased use of muscle glycogen after restricted activity is that hyperthermia caused exhaustion before muscle glycogen use was maximized.  The differences between rates of increase in rectal temperature in dogs after restricted activity and after exercise training appear to cause differences in exercise endurances because of the affect of rate of rectal temperature increase on hyperthermia.  Thus, dogs with higher rates of increase in rectal temperature can endure less exercise than dogs with lower rates because hyperthermia sets in more quickly as rate increases (Nazar et al. 1992).
 
 
 

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