Image provided by Kristy Oliver VN, DipAVN (surgical), RVT, VTS (physical rehabilitation), CCRP, CVPP, CCMT
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The use of water as a therapeutic modality in veterinary practice is becoming commonplace, but the therapeutic properties of water have been used in the human and animal world for hundreds of years. The Greeks were using public baths by 500 BC and the Romans had heated baths by 350 AD. Arctic monkeys realized that during the winter, hot springs kept them warm.
Hydrotherapy, a term used when water is a therapeutic modality,1 covers the use of exercises, such as swimming and walking on an underwater treadmill.2 Using the properties of water, for conditions identified as pre- and post-surgical, neurological and orthopedic, as well as for conditioning, patients can benefit from muscle relaxation, improved joint range of motion , muscle tone, strength and endurance.3
Water Properties
It is important to understand the properties of water and its effects on a body placed in it. Temperature, hydrostatic pressure, viscosity and buoyancy will all influence the patient.4 and should be taken into consideration when planning therapeutic exercises in water. The forces exerted on a solid body in water include gravity, drag, thrust, buoyancy and motion (Figure 1).
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Temperature
Water temperature is important, as are the thermal properties of water. The thermal conductivity of water is 0.6 mK, which corresponds to the exchange of thermal energy when a body comes into contact with water.5
Certain water temperatures can promote soft tissue relaxation, reduce pain, and facilitate circulation and tissue perfusion.6 while increasing the extensibility of the fabrics. The water temperature typically used in veterinary hydrotherapy ranges from 83 to 88°F. Care should be taken to monitor patients participating in hydrotherapy for signs of exhaustion and/or overheating, such as increased respiratory rate, lagging behind the underwater treadmill, and signs visuals of increased stress.
Hydrostatic pressure
Pascal’s law states that the pressure of a fluid is exerted equally on all surfaces of an immersed body at rest and at a given depth. This also means that pressure increases with fluid density and submergence depth and is expressed in pounds per square inch (PSI), which can be calculated as 1 PSI = pound of force (lbf) divided per square inch of the container. Some of these effects may result in benefits, such as reduced swelling in an area and reduced pain.4 As there is a measured amount of pressure related to water level, care should be taken in patients with cardiac, circulatory and respiratory diseases.
Strength and viscosity
Frictional resistance is created by cohesion or sticky character of fluid molecules.
Water is 15 times stickier than air, so it resists the movement in it. There is a decrease in resistance to flow and the resistance depends on the velocity, the velocity of the fluid and the shape of the body in the fluid. Water exercises can be tiring7 therefore, it is important to monitor patients for signs of fatigue, pain, lameness, and distress.
Buoyancy
Buoyancy is the force exerted on a submerged object and opposed to gravity.8 Archimedes’ principle states that when a body is partially or fully immersed in a fluid, it experiences an upward thrust equal to the weight of the displaced fluid. Therefore, as water depth increases, lift decreases. (Figure 29) When working with buoyancy, it is also important to understand specific gravity (SG), which is the ratio of the density of a substance to the density of a standard, usually water to a liquid or a solid. The SG of water is 1.0. An animal’s ability to “float” depends on GS. Animals with a lean body structure and lower amounts of body fat have an average SG of 1.10, while animals with a higher amount of body fat have an average SG of 0.93. Therefore, patients with lower OS may float a little better than others.
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Fluid dynamics
Fluid dynamics is a description and study of liquids and gases and in part involves the study of the motion of a given fluid. Laminar flow is the smooth or straight flow of water particles moving in a direction and speed where all molecules are parallel. Turbulent flow has a more chaotic, nonlinear motion in which water particles flow in all directions, creating more dynamic pressure differentials, so that resistance increases with speed.
Drag is anything that increases resistance. In the case of hydrotherapy in veterinary practice, drag relates specifically to coat, type and length, as all of these create drag and increase resistance.ten
Speed
A general rule of thumb is that the larger and longer the dog, the higher the speed of the treadmill belt to achieve a normal walking gait. Increased turbulence, resistance and friction can lead to increased effort. Movement, hair, weight and speed all influence overall physical exertion.ten
Swimming pool treadmill vs underwater treadmill (UWTM)
Swimming provides non-weight bearing exercise, is relatively low impact, is a great upper body workout with active range of motion (AROM) of all joints,11 in particular the forelimbs, which are more affected by an increased workload,12 and improves core and trunk strength. Davis et al. reported that hip range of motion was not significantly affected by swimming compared to walking.2
Patients who begin swimming should not be left unattended and a flotation device should be used to aid buoyancy. Care should be taken to ensure that the patient acclimatizes gently to reduce stress and anxiety, as not all patients can swim by nature. Excessive forelimb movements due to stress or anxiety will increase turbulent flow and make movement through the water more difficult, likely further increasing stress levels.
UWTM
Walking on an underwater treadmill can be a relatively more controlled form of water exercise. Less stress is placed on the joints and spine,13 making it a more suitable form of hydrotherapy for the early rehabilitation of patients. It can provide variable and adjustable weight-bearing exercises, improved AROM, proprioceptive gait training and better balance when walking, can build lean muscle mass, and is a starter for swimming. Patients also benefit from proprioception, which is the ability to identify the location and position of their own body part, which involves balance.14 It also allows engagement of the triceps brachii and quadriceps femoris, essential for weight-bearing and walking.
Conclusion
Hydrotherapy is developing in the veterinary field and constitutes an important tool for the rehabilitation professional. Hydrotherapy turns out to be an integral part of a multimodal approach to canine and feline physical rehabilitation. It can be used to introduce early weight-bearing exercises in post-operative patients, improve proprioception and balance in neurological patients, and contribute to improving joint range of motion in osteoarthritic patients, while contributing to the development of muscle mass, strength, and endurance.
Understanding the properties of water and the effects on the patient during hydrotherapy treatment will help the rehabilitation team provide the right type of hydrotherapy based on these factors.
Kirsty Oliver, VN, DipAVN (surgical), RVT, VTS (physical rehabilitation), CCRP, CVPP, CCMT, is a rehabilitation practitioner with Virginia Veterinary Surgery Centers. She earned her veterinary nursing degree from the Royal College of Veterinary Surgeons in the United Kingdom and obtained additional certifications in the United States.
The references
- Monk M. Hydrotherapy. In: Goff L, McGowan C, Stubbs N, eds. Animal Physiotherapy: Assessment, Treatment and Rehabilitation of Animals. Blackwell Editions; 2007: 187-206.
- Drum MG, Marcellin-Little D, Davis MS. Principles and applications of therapeutic exercises for small animals. Vet Clin North Am Small Anim Pract. 2015;45(1):73-90. doi:10.1016/j.cvsm.2014.09.005
- Corti L. Nonpharmaceutical approaches to pain management. Best Anim Med Companion. 2014;29(1):24-28. doi:10.1053/j.tcam.2014.04.001
- Torres-Ronda L, Del Alcázar XS. The properties of water and their applications for training. J Hum Kinet. 2014;44:237-248. doi:10.2478/hukin-2014-0129
- Nganvongpanit K, Boonchai T, Taothong O, Sathanwongs A. Physiological effects of water temperature in swimming toy breed dogs. Kafkas Univ Vet Fak Derg. 2014;20(2):177-183.
- Nganvongpanit K, Kongsawasdi S, Chuatrakoon B, Yano T. Change in heart rate during aquatic exercise in healthy small, medium and large dogs. Thai Journal of Veterinary Medicine. 2011;41(4):455-461.
- Tomlinson, R. Use of canine hydrotherapy as part of a rehabilitation program. The veterinary nurse. 2013;3(10):624-629. doi:10.12968/vetn.2012.3.10.624
- Lim CG. Effect of underwater treadmill gait training with water jet resistance on balance and walking ability in patients with chronic stroke: a pilot randomized controlled trial. Neurol before. 2020;10:1246. doi:10.3389/fneur.2019.01246
- Levine D, Millis DL. Percentage of normal weight bearing during partial immersion at different depths in dogs. Presented at: Second International Symposium on Rehabilitation and Physiotherapy in Veterinary Medicine; 2002; Knoxville, TN.
- Levine D, Millis DL, Flocker J, MacGuire L. Aquatic therapy. In: Levine, D, Millis, DL, eds. Canine rehabilitation and physiotherapy. 2nd ed. Elsevier. 2013: 526-542.
- Connell L, Monk M. Postoperative orthopedic rehabilitation of small animals. The veterinary nurse. 2010;1(1):12-21. doi:10.12968/vetn.2010.1.1.12.
- Johnston SA, McLaughlin RM, Budsberg SC. Non-surgical management of osteoarthritis in dogs. Vet Clin North Am Small Anim Pract. 2008;38(6):1449-viii. doi:10.1016/j.cvsm.2008.08.001
- Sims C, Marcellin-Little DJ, Waldron R. Rehabilitation and physiotherapy for the neurological veterinary patient. Vet Clin North Am Small Anim Pract. 2015;45(1):123-143. doi:10.1016/j.cvsm.2014.09.007
- Brundell K. Canine osteoarthritis: improving quality of life. The veterinary nurse2011;2(8):460-467. doi:10.12968/vetn.2011.2.8.460