Basics of Musculoskeletal Conditioning in Performance Dogs

Written by Holly Pollard-Wright DVM, CCRP
Owner/CEO of VETERINARY KINETICS REHAB Inc

Exercise itself has both a positive physical and psychological effect on the dog.^{1, 2, 3} Canine performance is a science in which athletic and working dogs usually perform tasks and activities at an energy level above that of the typical companion dog. Accordingly, the trained and conditioned canine athlete or working dog’s metabolism performs differently than the pet dog. For example, related to the healthy pet dog population at rest, the range for rectal temperature is 101°– 102.5° Fahrenheit (F), respiration rate is 10–30 breaths per minute, and heart rate is 70-160 beats per minute. In contrast, conditioned athletic dogs can exhibit normal metabolic variants related to heart rate, rectal temperature, and respiration.^{1, 2} 

Heart rate

Training and conditioning positively affect heart rate. In general, a dog’s heart rate usually increases with work, and heart rate will slow down once the work is performed. Work itself can cause an increase in heart rate, and the proper conditioning program prepares the dog’s body to handle higher levels of work.² For example, sled dogs showed that conditioning significantly decreased the working heart rates, although their resting rates were not greatly affected.⁴ Notably, many working dogs get very excited to work, and the act of work will release emotional energy stimulating an increase in the dog’s heart rate.^{2, 4} As cited in the literature, working dogs’ heart rates range from 115 – to 240 beats per minute.^{2, 4} 

Temperature

Normal recorded temperatures for working dogs are between 100° F – 108°F. The normal temperature values reported in the literature for working dogs include: Greyhounds 104°F – 106° F (47.5 – 41.5 C), Labradors, 102° F – 107°F (39.0 – 41.8 C), Pointers 103°F -106° F (39.5 – 41.2 C), and Sled Dogs 104° F – 108° F (40.0 – 42.2 C).^{2, 3, 4, 5}

Notably, these dogs did not show any clinical signs of heat-related illness, including heatstroke, a condition characterized by core body temperatures > °F 105.8°F, with central nervous system dysfunction. It results from a failure of the dog to dissipate accumulated heat during exposure to hot environments or during strenuous physical exercise under heat stress.⁶ 

Respiration rate

Working dogs’ respiration rates can vary from 100 breaths per minute (BPMs) to panting.² Body temperature and carbon dioxide (CO2) blood levels can affect a dog’s respiration. Work usually causes an increase in body temperature. In this process, work increases circulating CO2, resulting in an increased respiration rate.²  Respiration plays a role in maintaining the dog’s body temperature that prevents the body temperature from increasing to harmful levels. Importantly, dogs have minimal sweating capacity. They rely mainly on evaporative mechanisms through panting to thermoregulate, which maintains body temperature with tightly controlled self-regulation independent of external temperatures. 

Canine performance 

The dog’s peak athletic performance results from the correct anatomical build, conditioning, and psychological readiness to perform particular duties.^{1, 2} Both internal and external factors play a role in performance related to the canine athlete. Internal factors include anatomical make-up, physiological function, and psychological influence^{1, 2}.  Genetics, health, nutrition, training, and conditioning impact these internal factors.² In contrast, external factors include dog interaction, environmental climate and location, housing, type of work, and work factors.² There are three basic descriptors related to canine performance that are congruent with fundamental aspects to assess:²

1. The type of skill (or event) the dog will perform.
2. The performance definitions of this skill (or event).
3. The competition level and competition type required for this event.

There is more energy demand when the body performs at a level greater than its normal daily routine. When athletic needs increase, dogs must store energy in the body to achieve physical activity and utilize additional energy when physical activity is increased.¹ There is a proportional increase in the physical demands placed upon the animal’s body in this process. Therefore, a certain energy level is needed to maintain the dog’s tendency to monitor and maintain internal states, such as temperature and blood sugar, at relatively constant and stable levels.  

For this to happen, the energy systems of the dog’s body must be conditioned to produce, transport efficiently, and use energy in the location where it is required.¹ The body can adapt, to varying degrees, when short-term stress is placed on the system to meet altered demands. When repeated daily stress results in an altered daily routine producing energy systems conditioned to meet these new demands. Workout repetition results in adaption to meet altered demands by conditioning the body to the stresses of the new demands.¹ In this process, energy sources located in the areas with the most significant needs are pulled, thus playing a role in minimizing the chance of systemic or cellular injury. As such, conditioning of skeletal muscle involves performing a physical exercise that prepares muscles for a specific task.¹ Training pertains to incorporating the specific exercise into the type of sporting event or activity the dog will be involved.¹ Behavior modification required to perform the specific activity is also a part of training.¹ Endurance relates to the ability of a muscle or group of muscles to undergo many repetitions of contraction under low loads.¹ Endurance through exercise targets specific muscle groups involved in the specific action and for a prolonged time (usually greater than 15 minutes).¹ Dogs’ endurance exercises include trotting, running, swimming, land and underwater treadmill activities, and long-distance sled pulling.¹ 

Canine muscles 

An essential feature of mammalian skeletal muscle is diversity among fiber types.⁷ How the dog responds to a conditioning program may be affected by its fiber type composition. In general, the dog’s muscle fiber types are divided into type I slow-twitch and type II fast-twitch fibers.¹ The type I/type II ratio of the muscle fiber types in a particular muscle is genetically predetermined.¹ A higher percentage of type I fibers populate the muscles responsible for maintaining posture. In contrast, a higher percentage of type II fibers are present in muscles responsible for speed and power.¹ Some literature suggests that muscle fiber composition changes may occur with specific conditioning.¹ The conditioning program of a rehabilitation program places energy demands on muscles that include motoneuron discharge patterns.^{1, 7} In this process, the loading conditions on the muscles are a significant determinant of contractile performance.^{1, 5, 7}

Common hindlimb sports medicine conditions

There can be times when an activity stresses any dog’s metabolic processes to extremes. In this process, change in performance can be attributed to an anatomical lameness, a medical illness or imbalance, or a psychological alteration.²

Exercise-induced medical problems can occur when:  

1. A dog is involved in an activity that stresses the body’s metabolism beyond where it can function.  
2. A specific activity exposes an underlying problem, or the particular activity causes a medical problem.  

Two scenarios that may include exercise-induced medical problems:

1.  An under-conditioned dog participates in an activity or work environment to which it is not acclimated to handle.²
2. A properly conditioned dog (or athletic dog) engages in activity above the level that it is prepared to handle.² 

Iliopsoas muscle strain and cranial cruciate ligament insufficiency are the most common hindlimb orthopedic/sports medicine conditions afflicting performance and working dogs.¹ Iliopsoas strain is an overstretching injury that may result from excessive stretching or stretching when the muscle is activated.¹ Studies indicate that muscles that cross multiple joints or those with complex architecture have increased susceptibility to strain injury.¹ In addition, injured muscle is weaker and has reduced tension, thus increasing the risk of re-injury. Appropriate rehabilitation therapy related to iliopsoas muscle strain initially focuses on relieving pain and allowing for complete healing to prevent re-injury.¹ This treatment is followed by muscle strengthening, endurance, and flexibility that includes proper warm-up and stretching techniques to further reduce the incidence of re-injury.¹ Cranial cruciate ligament (CrCL) insufficiency is a degenerative condition that is a common cause of pelvic limb lameness and osteoarthritis in dogs.⁸ Surgical therapies developed to treat dogs with naturally occurring CrCL insufficiency aim to address the resultant instability.⁸ Appropriate rehabilitation after surgical intervention emphasizes endurance training, and strength and stabilization training.¹

Principles of Muscle Conditioning

1. Sports-specific conditioning ensures optimal neural patterning and correct timing through two general categories of conditioning programs: strength-power programs and endurance programs. Metabolic changes depend on the principles of intensity, duration, frequency, and training method.^{1, 9} The speed and contraction of muscles, such as high intensity (through recruitment of fast-twitch muscle fibers) vs. low intensity (through recruitment of slow oxidative fibers), will cause specific training effects.⁹ In this process, central and peripheral physiological changes occur because of conditioning. Central changes include alteration to the cardiovascular, pulmonary, and endocrine systems. Peripheral changes occur in the musculoskeletal system.¹ Specificity describes training that uses the systems and structures involved in the activity. For example, a dog that competes in a sport that requires pulling loads would be better served to run while pulling against resistance instead of jogging for a long distance on a treadmill.¹ Accordingly, if the program’s purpose is to increase strength, short duration, maximal intensity workouts are recommended. This type of program affects peripheral conditioning more than central conditioning.¹ If the goal of the conditioning program is an increase in speed, include sprint workouts at maximal intensity. If the program’s purpose is to increase endurance, long-duration workouts of submaximal intensity are recommended. In this process, endurance conditioning improves the aerobic capacity to provide energy and conditions the musculoskeletal system to use energy more efficiently.¹ Workouts that include exercise for the spinal muscles should be included because it has been theorized that the spinal muscles are the first to fatigue during sprinting.¹⁰ Uphill sprint running helps to strengthen and condition spinal muscles. Running with resistance helps build body strength. Running with a harness and pulling is an example of resistance running.  
2. The overload principle refers to increasing speed, resistance, number of repetitions, frequency or duration of sessions, and decreasing recovery time.^{1, 9} Exercise aims to target a system to a level beyond what is accustomed, and this applies to the cardiovascular system, the musculoskeletal system, and other body systems.¹ In this process, the system is placed in an overloaded state, causing it to adapt to new conditions. A system’s ability to perform a task at a higher level of performance is improved, such as increased strength, power, or endurance. As such, the intensity, duration, and frequency of a particular exercise influence overload. 

Proprioception and spinal muscles

The perception or awareness of the position and movement of the body includes nerve impulses from joints, muscles, and tendons.^{9, 10} The canine athlete receives information about the joint position, motion, vibration, and pressure in this process. When nerve endings and pathways are damaged, this causes the impaired segmental transmission of nerve impulses, resulting in impaired balance, decreased coordination, diminished joint position sense, and altered reflexes when performing movements.⁹ Weight-bearing provides proprioceptive input, and dogs naturally bear approximately two-thirds of their weight on their forelimbs.^{1, 10} Accordingly, proprioception is foundational to the fitness of the canine athlete that helps ensure the performance of physical activities without injury.¹⁰ Proprioception plays a role in activities that include running, jumping (up and down), navigating unstable surfaces, and quickly or abruptly changing direction.¹⁰  Proper development of a dog’s musculoskeletal system includes exercises with spinal muscles.

Proprioceptive training plays a significant role in ensuring optimal biomechanical alignment.^{1, 10} 

References 

1. Millis, D. L., & Levine, D. (2014). Canine rehabilitation and physical therapy (2nd ed.). Saunders, Cop.
2. Robert L. Gillette, T. Craig Angle, Jennifer S. Sanders, Fred J. DeGraves, 2011. An evaluation of the physiological affects of anticipation, activity arousal and recovery in sprinting Greyhounds/ Applied Animal Behaviour Science 130 101–106
3. Matwichuk, C.L., Taylor, S.M., Shmon, C.L., Kass, P.H., Shleton, G.D., 1999. Changes in rectal temperature and hematologic, biochemical, blood gas and acid-base values in healthy Labrador Retrievers before and after strenuous exercise. Am. J. Vet. Res. 60, 88–92.
4. Angle, T.C., Wakschlage, J., Gillette, R.L., Stokol, L., Geske, S., Adkins, T.O., Gregor, C., 2009. Hematological, serum biochemical and cortisol changes associated with anticipation of exercise and short duration high intensity exercise in sled dogs. Vet. Clin. Pathol. 38, 370–374
5. Rose RJ, Bloomberg MS 1989. Responses to sprint exercise in the greyhound: effects on haematology, serum biochemistry and muscle metabolites. Research in Veterinary Science, 47(2):212-218]
6. Pathophysiology of heatstroke in dogs – revisited. (2013). Temperature. https://dx.doi.org/10.1080%2F23328940.2017.1367457
7. Toniolo, L., Maccatrozzo, L., Patruno, M., Pavan, E., Caliaro, F., Rossi, R., Rinaldi, C., Canepari, M., Reggiani, C., & Mascarello, F. (2007). Fiber types in canine muscles: myosin isoform expression and functional characterization. American Journal of Physiology-Cell Physiology, 292(5), C1915–C1926. https://doi.org/10.1152/ajpcell.00601.2006
8. Tinga, S., Kim, S. E., Banks, S. A., Jones, S. C., Park, B. H., Pozzi, A., & Lewis, D. D. (2018). Femorotibial kinematics in dogs with cranial cruciate ligament insufficiency: a three-dimensional in-vivo fluoroscopic analysis during walking. BMC Veterinary Research, 14(1). https://doi.org/10.1186/s12917-018-1395-2
9. James L. Cook1, D. V. M., & Steven P. Arnoczky2, D. V. M. (2015). World Small Animal Veterinary Association World Congress Proceedings, 2013. VIN.com. https://www.vin.com/apputil/content/defaultadv1.aspx?pId=11372&meta=generic&catId=35317&id=5709895&ind=265&objTypeID=17
10. Farr, B. D., Ramos, M. T., & Otto, C. M. (2020). The Penn Vet Working Dog Center Fit to Work Program: A Formalized Method for Assessing and Developing Foundational Canine Physical Fitness. Frontiers in Veterinary Science, 7, 470. https://doi.org/10.3389/fvets.2020.00470