FITNESS TRAINING AND CONDITIONING
Fitness is a general term used to describe the ability to perform physical work. It requires cardiorespiratory function, muscle strength, endurance, and flexibility. Fitness is a lifelong adaptation of the cardiovascular and musculoskeletal systems to exercise. Conditioning is the performance of specific physical exercises to prepare mentally and physically for the performance strenuous activity. A fit and conditioned athlete requires an owner, trainer, or handler’s conscientious commitment to a well-rounded conditioning program. Training of the musculoskeletal and cardiopulmonary systems is a fundamental part of conditioning. Training is used to teach sporting dogs the specifics of sporting activities. Training also influences the dog’s behavior. Conditioning starts early in life. Strenuous exercise is not recommended before closure of the growth plates of long bones so as to avoid fractures or trauma to these growth plates. Physeal closure occurs at approximately 10 months of age in large dog breeds, a few months earlier in small dog breeds, and a few months later in giant dog breeds. Before physeal closure, the conditioning of sporting dogs involves play with siblings and self-motivated activities (eg, walks, runs). It is important to make efforts to rule out developmental orthopedic diseases (DODs) in dogs chosen as future sporting dogs. This may be done by assessing the sire and dam, by performing an orthopedic examination at approximately 4 months of age, and by making radiographs of hip and elbow joints. Many physical attributes important to sporting dogs are inherited. These include size, speed, strength, endurance, and agility. The relative importance of these attributes varies greatly between sports (Table 1). Conditioning may be effective around puberty, when a surge in androgen hormones occurs in male dogs. This surge in androgens may help to promote muscle development. Despite differences in muscle mass and size between male and female sporting dogs, there are no clear differences in performance between male and female dogs, including racing Greyhounds. The response to aerobic training increases after puberty in human beings. Similarly, sexual maturity likely has an impact on the response to training in dogs. Complete and balanced nutrition is critical to the conditioning and maintenance of sporting dogs. Nutrition is particularly important during growth, because excessive energy and calcium may increase the expression of faulty genes in dogs genetically predisposed to DODs. Nutrition has to be adapted to the metabolic needs of working dogs during training and during the competitive period. These requirements may be dramatically increased during competitive periods (ie, a sled dog running 12 hours per day). Sled dogs have unique nutritional requirements resulting from their exercise profile. One study reported that sled dogs fed an extreme diet with no carbohydrate (39% protein and 61% fat on an energy basis) fared better than dogs receiving diets rich in carbohydrate (23% and 38% carbohydrate) Feeding of sporting dogs should not occur during periods of strenuous exercise. Gastric emptying was delayed by exercise lasting more than 1 hour in untrained dogs. Hydration is also critical to sporting dogs, particularly when exercising in hot conditions. Conditioning involves a physical effort placed on the cardiopulmonary system. Exercise increases heart rate and influences blood pressure in dogs. Over time, exercise also increases red blood cell counts. Conditioning lowered the thyroid hormone concentration (T4 and free T4) in sled dogs in one study. Heart rate monitoring during exercise has been used in dogs. Exercise more than doubled the incidence of cardiac arrhythmias in Greyhounds in one study. Heart rate during exercise is higher in overweight dogs than in lean dogs. Training leads to an adaptation of the cardiovascular system over time. Although little is known about the specific changes occurring in heart rate at rest, during, and after exercise in sporting dogs, training leads to a lower resting heart rate and a lower resting blood pressure in people. This is particularly true for endurance training, but it also occurs in response to strength training. Training also boosts aerobic fitness in children and adolescents. Although little is known about the relation between fitness and body fat in dogs, people with lower body fat tend to be fitter than people with higher body fat. Exercise leads to a decrease in body fat in people. The parameters evaluated when assessing a dog that is destined to be a working dog include its size, conformation, gait during general and specific activities, past and current orthopedic health, body condition score, fitness level, and behavior (eg, level of socialization, drive to perform, extraverted or introverted nature). Fitness and endurance may be evaluated in dogs by running on a treadmill, doing a 6-minute walk test, or by assessing performance during outdoor activities. In one report, control dogs walked 573 85.5 m in 6 minutes. Physiologic (eg, heart rate, rectal temperature) and hematologic (eg, plasma creatine kinase, plasma lactate) factors are evaluated during fitness tests. Endurance is adversely affected by restricted activity. Endurance decreased by 41% in 10 dogs whose activity was restricted for 8 weeks. These changes were reversible in 8 weeks of retraining. When designing a training program, frequency, intensity, and duration of exercises are chosen. The frequency is the number of exercise bouts per time period (per session, day, or week). The intensity is the load applied (eg, speed of trotting or galloping, weight used). The duration is the number of repetitions (in range of motion [ROM], jumping, or catching) or the length of time of exercise. Excessive frequency, intensity, or duration may have a negative impact on training, irritate an existing condition, or cause an injury because of insufficient rest, excessive muscle or cardiovascular fatigue, or excessive stress placed on tissues during activity. To our knowledge, there is no scientific information describing the optimal training amount for conditioning and maintenance of sporting dogs. In people, recommendations for maintenance of fitness include 30 minutes of moderate-intensity activity per day.