By Brennen McKenzie, MA, MSc, VMD, cVMA

It is well established that exercise has health benefits in humans. Regular physical activity can significantly reduce the occurrence of age-associated diseases and help maintain and restore function in humans of any age.^1-4 However, what about dogs and cats? Is it time to start a chain of canine and feline fitness centers?

Fitness for pets

From the perspective of basic physiologic principles, there is no reason dogs should not benefit from exercise just as humans and other animals do. Dogs respond to cardiovascular conditioning and strength training exercise with similar physiologic adaptations as humans, increasing their aerobic fitness and strength.^5-10 Cats can respond to strength training with muscle development, but it is unclear whether they adapt to forced aerobic exercise in the same way dogs and humans do.^11,12

Unfortunately, there is virtually no research evidence directly evaluating the impact of exercise interventions on health outcomes or longevity in cats or dogs.

Just as in humans, one of the biggest risk factors for illness and premature death in cats and dogs is obesity.^13,14 Low levels of exercise are associated with an increased risk of obesity in both species, so it is possible regular physical activity may be protective against becoming overweight.^9,15,16

A few studies have investigated exercise as an adjunct to caloric restriction for weight loss in dogs. Some have found benefits, but not all, and it is clear that exercise without caloric restriction is unlikely to be an effective treatment for obesity.^9,17 However, overweight dogs may still benefit from exercise during dieting in other ways, such as preserving lean body mass and maintaining general fitness and function.¹⁸

Additionally, there is little evidence to determine whether or not exercise interventions would be practical or effective in facilitating weight loss in cats.¹⁹

Exercise may also improve comfort and function in dogs with osteoarthritis beyond the benefits associated with weight reduction.²⁰ Exercise has also been shown to have potential benefits in some non-musculoskeletal health conditions. One study found an exercise program had additive benefit to prednisone therapy in dogs with chronic diarrhea, improving appetite and weight, as well as symptom control.²¹ Similar studies in cats have not been published.

As in humans and in laboratory animal models, exercise appears to modify metabolic pathways associated with glucose metabolism in beneficial ways, at least in some dogs under some circumstances.^22,23 These same pathways are implicated in the effects of caloric restriction on health and longevity, which suggests exercise could extend health span and lifespan in dogs by mechanisms similar to those demonstrated in other species.^24,25

Rehabilitation

One area in which exercise for companion animals is most intensively studied is the relatively new and expanding field of rehabilitation medicine (more typically referred to as "physical therapy" in the human medical domain). Though the research base is still quite limited for many rehabilitation practices, the growth of this field has encouraged research into the effects of various kinds of exercise in dogs and cats.

One clear conclusion of this research is the opposite of activity, immobilization, is harmful. Indeed, immobilization reduces bone and muscle mass and function in dogs, as in humans and, as mentioned previously, lower levels of voluntary activity appear to be associated with obesity in both dogs and cats.^9,15,16

While various types of passive and active physical therapy exercises appear to have benefits for dogs with orthopedic conditions and recovering from orthopedic surgery, the details of which types of exercise, what intensity, what frequency, and many other important variables in rehabilitation medicine are poorly studied and based currently on hypotheses and clinical experience more than controlled research evidence.²⁶

Fitness—the capacity for aerobic exercise—declines with age in dogs as it does in humans.¹⁵ Along with orthopedic disease and other age-related changes in health, this loss of fitness may be part of the reason older dogs are less active than younger individuals. Regular exercise, including aerobic activity and strength training, helps elderly humans maintain function longer. Such activity will likely also be beneficial for geriatric dogs, and possibly for cats despite some differences in their natural patterns of physical activity.

We lack specific research evidence for the optimal type and amount of exercise likely to be beneficial to dogs and cats. Some efforts have been made to define basic parameters for assessing fitness and structuring exercise programs for healthy dogs, but there is negligible empirical validation for these proposals so far.²⁷

Similarly, while the field of veterinary rehabilitation is developing rapidly, few specific exercises for prevention or treatment of musculoskeletal disease are based on robust experimental evidence.²⁶ Finally, while we know exercise can have significant impact on morbidity and mortality in human populations, the evidence for this in dogs and cats is sparse.

Importance of moving

We know many pets lead excessively sedentary lives and suffer from obesity, which has demonstrable negative health effects. It is likely these pets would benefit from increased activity, both in terms of improved weight management and in general health. This is especially true for older pets, for whom owners and veterinarians may assume negligible physical activity is simply a manifestation of normal aging.²⁸ Older humans clearly benefit from physical activity, and the same is almost certainly true for older veterinary patients.²

Apart from the likely benefits of exercise for dogs, encouraging more exercise for our canine patients very likely also benefits their owners. Dog ownership alone has been associated with better outcomes in people for both mental and physical health, particularly in reducing cardiovascular disease risk.²⁹

The strongest evidence supports the psychological and physical benefits of exercise associated with dog walking. Studies reveal dog owners who walk their dogs get more physical activity than people without dogs, and the American Heart Association has concluded dogs may provide a sufficient degree of cardiovascular risk reduction to their owners.²⁹

Unfortunately, many dog owners do not walk their dogs, and this removes the potential benefits of exercise for both pet and owner. Veterinarians can potentially play a role in improving not only the health of our patients, but of our clients by encouraging dog owners to walk with their dogs and participate in other joint exercise. Though clients may seem resistant to recommendations for increased activity and weight reduction in their pets, there is evidence veterinarians can successfully influence these behaviors.^30-34

It is critical we are as proactive as possible, aiming for prevention of disease where we can as well as detection and treatment of disease once it emerges. Exercise is a well-established component of preventive medicine in humans, and it is appropriate to extrapolate cautiously from this while also actively developing real evidence to support specific therapeutic and preventative exercise recommendations.

More research is needed, but it is highly likely increased physical exercise is beneficial for cats and dogs in maintaining health and slowing aging. There's also plenty of evidence showing exercising with our dogs is good for our health. So, take your dog for a walk right now!

Brennen McKenzie, MA, MSc, VMD, cVMA, discovered evidence-based veterinary medicine after attending the University of Pennsylvania School of Veterinary Medicine and working as a small animal general practice veterinarian. He has served as president of the Evidence-Based Veterinary Medicine Association and reaches out to the public through his SkeptVet blog, the Science-Based Medicine blog, and more. He is certified in medical acupuncture for veterinarians. Columnists' opinions do not necessarily reflect those of Veterinary Practice News.

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