Preventing injury in sporting dogs--from oxidant stress to osteoarthritis (Proceedings)

When we think of sports for dogs we usually think of racing and coursing or luring as with greyhounds; or of field trial dogs for hunting, or even sled dogs in the Iditarod. However, within the last 10 years or so, other sports have been gaining in popularity including agility, flyball, disk dogs (Frisbee catching), tracking for search and rescue, dock jumping and earthdogs. Over 800,000 entries in 2,147 American Kennel Club sponsored agility trials were recorded in 2008 alone. Flyball associations are now located in North America, the United Kingdom, Belgium, Australia, South Africa, Germany, Finland, and the Netherlands and in the US alone, over 8,000 entries were recorded by the North American Flyball Association.

With many of these increasingly popular sports, there is no specific breed requirements and because “anyone can play” many pet owners enroll their dogs in these activities without prior knowledge of the sport on the part of the owner, and little to no training on the part of the dog. A major concern for veterinarians is that little to no research has been conducted to determine the effect of these sports on the dogs, what training is needed, and what is required to prevent injury or serious chronic disease in the participants.

Fitness in dogs has not been fully defined and no physiologic studies have adequately determined the fitness of the dog. In humans, maintenance of fitness is often defined as at least 30 minutes of moderate-intensity activity per day. The fitness of the dog should be determined by the sport participated in. Sled dogs require quite a different fitness level than agility dogs. Sled dogs are required to have high endurance and strength to pull a sled many hours over long distances and rough terrain in a day. Their training should reflect that effort and try to mimic the conditions as much as possible. The sled dog must be exercised for extended periods every day and be required to strengthen muscles as well, so that swimming would not be an appropriate exercise since it would not place the stress and strain that a sled would on the musculoskeletal system.

However, swimming would be an appropriate exercise for dock dogs, along with short sprints on land. Fitness must also be geared not only to the type of sport but also to the breed and age of the dog. Brachicephalic breeds do not have the cardiopulmonary capabilities that dolicocephalic breeds do and are more likely to develop heat stroke, just as older dogs are more likely to develop heat stroke than their younger counterparts. To achieve the best state of fitness for the sport the dog participates in, requires careful conditioning specifically tailored to the individual. Conditioning that is appropriate for the individual will prevent injury while overtraining will induce injury and inadequate conditioning will predispose to it.

Beginning conditioning too early for a puppy may result in trauma to growth plates and exposes the immune-incompetent dog to potentially hazardous pathogens. I have treated a 4 month-old Labrador Retriever for severe pneumonia, lung abscess and pyothorax. He had been training at a kennel where he was exercised 2 to 3 hours a day and housed with many other dogs. Most sports medicine veterinarians recommend to not begin training until growth plate closure which depends on the size of the breed and can be anywhere from 10 months to 18 months of age.5 Puppies should be exercised daily, but on forgiving surfaces with good traction such as turf, not on cement or asphalt.

The specific skills required of the canine athlete depends upon the sport the dog is participating in and will gear practice and training as well as how injury will occur. Racing and coursing dogs can be subject to stress fractures since they often race on hard surfaces without shock absorption. The skills they require are speed and strength. They are also subject to muscle body rupture, including gracillis rupture.

Field trial dogs also require speed and strength but agility is important as well to navigate the unpredictable terrain. Field trial dogs must also be acclimated to the environment or risk heat stroke and severe dehydration. Hunting dogs often travel long distances but need only short bouts of strength so training may be geared toward sprinting, keeping in mind the often difficult terrain they face as well. Herding dogs, similar to sled dogs, must have endurance for the long arduous task ahead. Agility dogs must be able to sprint, make sharp turns (balance) and of course, be agile, to run the course without injury.

These skills require not as much strength as practice to prevent injury. Search and rescue dogs must have endurance similar to sled dogs, while being able to navigate in never-before experienced conditions. They must also have excellent balance or proprioception to remain uninjured in conditions where their safety may be in jeopardy. Flyball dogs certainly require strength for the speedy navigation of the jumps but also must practice regularly to prevent injury- the dogs must be taught how to hit the platform and catch the ball in a manner that will not predispose them to chronic overuse injuries.

Conditioning of the athlete requires the owner, trainer and dog to perform physical activity on a regular basis in order to fully be prepared to perform the sporting activity they are a participant of to the best of the dog's ability with the least likely chance of injury. While there are no clear differences in abilities between male and female dogs, conditioning at the time of puberty, at least in males, may promote muscle development and thereby promote strength and speed.

Delaying gonadectomy in larger breed dogs may reduce the incidence of some orthopedic diseases including hip osteoarthritis, cruciate ligament disease, and other problems related to delayed growth plate closure in sex-hormone deficient puppies. Conditioning in pubertal age and young adult dogs regardless of sex status must be controlled to prevent permanent injury since most of these dogs are highly motivated to perform until exhaustion and do not have the proprioception to prevent injury to tendons, ligaments, and articular cartilage.

Regular conditioning prevents loss of physical fitness (both muscle strength and endurance) in dogs and humans. Activity restriction for 8 weeks causes a 41% loss of endurance in dogs and requires 8 weeks of recovery to regain the original level of fitness.10 The frequency of training depends upon the sport involved and whether endurance fitness is a large factor. Sled dogs need much more frequent training to be able to perform in competition multiple hours (and days) in a row. Flyball dogs need frequent enough exercise to build muscle for strength and speed but not as much as sled dogs who perform for over 12 hours in a day. Adequate rest is required as well as frequent training sessions in order to prevent injury and to allow tissues to restore normal electrolyte and lactate levels to the intensely worked tissue. Lactate has returned to pre-exercise levels within 4 hours following agility exercise in dogs and in less than 30 minutes following a race in Greyhounds.

Regular practice significantly improves performance in dogs participating in agility competition. Even when breed, sex, age and height were controlled for, dogs with more hours of practice were more precise as well as generally faster through a course. Herding skill development increases with the handler's experience but also is independent of the handler and increases with practice in herding dogs. Interestingly enough, even in Greyhounds, training and time spent training leads to peak performance and takes approximately 9.1% of the dog's life to achieve, a similar amount of lifespan spent training to peak performance in elite human track runners. The period of practice, training, conditioning and development of expertise, then, is vital for an athlete to reach peak performance. With the development of expertise, it is also likely that there is a decrease in injury as well.

Strengthening exercises are required for all sporting dogs as part of their conditioning program. Most exercise physiologists consider specificity to be the principle of applying exercises that will strengthen the muscles used for the particular sport and in an environment that is similar to the environment encountered in competition. The exercises used regularly in training will most likely mimic the type of sport but early in the conditioning process may be less strenuous than the exercise encountered during competition. Once an individual has developed skill and strength during training with the exercises, they will eventually exceed the work encountered during competition. This is the overload principle, which means that in order to increase fitness and performance, the muscle or cardiovascular system must exceed its current metabolic limit. Strengthening exercises can take on many different modalities including uphill exercise, elastic band exercise, body weights, pulling a cart, dancing or wheelbarrowing.

The development of aerobic endurance requires sustained aerobic exercise for longer than 15 minutes at a time. With endurance training, there is a development of muscle vascularization to improve oxygen delivery, improved cardiovascular efficiency, increased oxidative enzymes to increase ATP synthesis, and improved strength of bones, muscle and tendon. The long-term benefits of endurance exercise far outweigh the risks and indeed does not appear to increase the incidence of osteoarthritis in dogs. Development of muscle with consistent conditioning may actually prevent development of OA or at least slow its progression.

For the athlete, this is of vital importance toward achieving peak performance before older age. A decline in physical ability does occur in age but may be delayed by maintenance of physical fitness.  Part of this decline may be due in part to reduced proprioception with increasing age. Improved performance occurs with improved balance and proprioception as well as reduces strain of tendons and wear of articular cartilage. Thus any conditioning program must include balance and proprioception exercises including wobble boards, cavalettis, elastic bands, figure of eight turns, etc. These exercises must be performed regularly in order to have a lasting effect and significant improvement of fitness.

All of these factors must be considered when becoming part of the canine athlete's team. The focus for veterinarians is on preventing injury but that just naturally results in improved performance as well so that most goals of the trainer are also those of the veterinarian.

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