Does Exercise Help Your Pet's Immune System?
You better believe it; exercise has a profoundly beneficial effect on your pet's immune system. Watch out though; too much exercise can actually be harmful. Read on to find out exactly how moderate exercise can give your pet's immune system an added boost.
Natural Killer Cells
Natural Killer (NK) cells are part of the body's first line of defense. They're always actively looking for virally infected cells or tumors. Cells that aren't quite right will provide clues, often advertising their malady by releasing certain chemicals or presenting certain particles on their membranes. NK cells pick up on this and respond by injecting toxic particles into the diseased cell, preventing it from causing any further harm. Researchers have found that the cytotoxic (cell-killing) ability of NK cells increases during moderate exercise, while slowly returning back to normal after exercise is ceased. This increased activity, when performed regularly, could help clear your pet's body of particularly stubborn tumors or infected cells.
Another part of a dog's first line of defense is the neutrophil. Neutrophils are the most numerous kind of white blood cell, making up 50-60% of the entire white blood cell population. They target all sorts of pathogens for destruction, including viruses, bacteria, fungus, protozoa, tumors, and virally-infected cells. They're considered phagocytic (cell-eating) and kill their targets by ingesting them. Exercise stimulates the production of neutrophils in the bone marrow while effectively increasing the phagocytic activity of existing neutrophils. It has also been shown that exercise lasting longer than 30 minutes can cause a second, delayed increase in neutrophil function.
When a cell detects something amiss in its internal physiology, something that could be fatal to the cell, it starts the process of apoptosis sometimes called cell suicide. Cells can either die by necrosis or apoptosis. Necrosis is the equivalent of accidental death within tissues of the body, while apoptosis is programmed cell death. The immune system spends less time cleaning up an apoptotic cell versus a necrotic cell. It is also known that apoptosis creates less inflammation than necrosis. Apoptosis is therefore generally desired, allowing the immune system to focus its energy on more pressing matters, like infection. Apoptosis has been previously shown to accelerate immediately after exercise. Such an increase is thought to keep inflammation low and the immune system functioning optimally.
Too Much Exercise
As you can see, regular moderate exercise is extremely helpful for your dog and its immune system. Keep in mind, though, that prolonged and strenuous exercise can depress your dog's immune system, leaving it more susceptible to infection. With prolonged exercise NK cell function decreases for up to 6 hours afterwards, neutrophil function is temporarily down-regulated, and the proliferative response of lymphocytes is suppressed. There is also an increase in cytokine release after strenuous exercise, causing inflammation that can distract the immune system. Keep the immune system of your dog performing at its best by providing 20 to 30 minutes of exercise every day. Play fetch with a ball or a Frisbee, go for a walk or jog, just get them outside and moving! Chances are you'll receive the added bonus of getting a little exercise yourself.
Photo Credit: Dave Halley