In recent years, the field of canine hydrotherapy has seen an encouraging surge in published research. With increasing clinical demand and professional interest, hydrotherapy is evolving from anecdotal practice into an evidence-informed modality with growing biomechanical, physiological, and therapeutic relevance. In this updated overview, we’ve structured the literature thematically to make it easier for Vetrehabbers to extract insights aligned with their case needs.
From kinematic changes in limb and spine motion, to physiological responses and targeted rehabilitation strategies for joint conditions, each study contributes a unique piece to the puzzle. While limitations remain and more research is still needed, particularly within specific patient populations, this collection of studies provides a strong foundation for building safe, effective, and individualized hydrotherapy protocols.
A. Biomechanics & Kinematics of Hydrotherapy
Limbs kinematics of dogs exercising at different water levels on the underwater treadmill, by Bliss & Terry (2023)
Bliss and Terry examined the impact of water depth on both forelimb and hindlimb joint motion in 10 healthy dogs using an underwater treadmill (UWTM), comparing four depths (digits, tarsus, stifle, hip) against dry treadmill walking at a consistent speed. Key findings included consistent increases in flexion across most joints, especially the elbow, stifle, and tarsus, with limited effect on joint extension. Shoulder flexion increased only at higher water levels, and hip motion changed minimally. These insights support using targeted water levels to influence specific therapeutic goals.
Investigating the effect of four water depths on canine forelimb kinematics during walking on an underwater treadmill, by Seychell & Tabor (2022)
This study evaluated forelimb joint angles in eight healthy dogs walking at four water depths: dry, mid-carpus, mid-ulna, and mid-humerus. Shoulder and carpal flexion increased significantly with water depth, with the greatest flexion observed at mid-humerus and mid-ulna levels, respectively. Elbow flexion increased with depth but did not reach statistical significance. Joint extension, stride length, and stride frequency were unaffected by water depth.
A single hydrotherapy session increases range of motion and stride length in Labrador retrievers diagnosed with elbow dysplasia, by Preston & Wills (2018)
This study compared healthy dogs to dogs with ED, assessing their elbow range of motion and stride parameters while walking on a treadmill, before and after a single hydrotherapy session. Both groups of Labradors had a greater range of motion in their elbows after swimming, but the ED group showed a greater improvement. All dogs had an increased stride length after swimming.
A comparison of stride parameters and carpal and tarsal joint angles during terrestrial and swimming locomotion in domestic dogs, by O’Rourke & Wills (2021)
Stride length and frequency were reduced in swimming vs trotting. Maximum carpal and tarsal flexion were greater in swimming. Tarsal extension was greater during trotting. Overall, ROM increased due to increased flexion during swimming.
A comparison of apparent neck and back angles before, during and after canine hydrotherapy, by Birch & Simms (2021)
There were no significant differences in neck and back angles before and after hydrotherapy. A flatter topline was observed during swimming. Use of a life jacket, harness or no aid did not alter spinal posture.
A study using a canine hydrotherapy treadmill at five different conditions to kinematically assess range of motion of the thoracolumbar spine in dogs, by Hodgson, Blake & de Godoy (2023)
Spinal motion was assessed under five treadmill conditions, including dry and inclined UWTM. ROM at T1, L3 and L7 increased significantly with incline, but water did not add or reduce spinal motion. These findings suggest incline UWTM may be safe post-spinal surgery.
Effects of a flotation vest and water flow rate on limb kinematics of Siberian huskies swimming against a current, by Fisher et al. (2021)
Stroke frequency increased when dogs swam without a flotation device or against current. Limb excursion increased significantly with water flow and decreased with flotation aid. Carpal motion exceeded tarsal.
The ‘dog paddle’: Stereotypic swimming gait pattern in different dog breeds, by Fish et al. (2021)
Swimming gait was consistent across breeds. The power phase (particularly in forelimbs) was shorter but faster than the recovery phase. Stroke frequency was inversely related to body size.
The effect of water depth on limb kinematics of the domestic dog during underwater treadmill exercise, by Barnicoat & Wills (2016)
Increasing water depth increased swing phase duration and stride length while decreasing stride frequency. Duty cycle was reduced with deeper water.
Kinematic analysis of the hind limb during swimming and walking in healthy dogs and dogs with surgically corrected cranial cruciate ligament rupture, by Marsolais et al. (2003)
Swimming increased ROM of the stifle and tarsus in all dogs, though hip ROM only increased in healthy dogs. Surgical dogs had reduced stifle ROM in both walking and swimming.
Aquatic treadmill water level influence on pelvic limb kinematics in cranial cruciate ligament-deficient dogs with surgically stabilised stifles, by Bertocci et al. (2020)
Stifle flexion was highest at stifle and hip water levels. Hip flexion increased at hip level. Stance phase duration decreased with increased water height.
B. Muscle Activation & Load
The impact of water depth and speed on muscle fibre activation of healthy dogs walking in a water treadmill, by Vitger et al. (2021)
Biceps femoris and vastus lateralis muscle activation increased with speed and water depth. Biceps femoris showed greater activation overall. Mid-femur water level imposed the greatest muscular demand.
Effect of water depth on muscle activity of dogs when walking on a water treadmill, by Parkinson et al. (2018)
Surface EMG revealed that gluteus medius and longissimus dorsi activation decreased with deeper water. Gluteus activation increased at tarsal level. Body position and lateral flexion may have influenced results.
Effects of partial immersion in water on vertical ground reaction forces and weight distribution in dogs, by Levine et al. (2010)
Weight-bearing decreased by 15% at stifle depth and 62% at hip depth. Forelimb weight-bearing increased at hip-level water. Early insight into hydro-assisted unloading.
C. Protocol Development & Therapy Planning
Safety of early postoperative hydrotherapy in dogs undergoing thoracolumbar hemilaminectomy, by Mojarradi et al. (2021)
83 dogs began hydrotherapy within 5 days post-op. Complication rates were comparable to other studies not using early hydrotherapy. Results support cautious use of hydrotherapy early in post-op care.
Effects of hydrotherapy and low level laser therapy in canine hip dysplasia, by De Oliveira Reusing et al. (2021)
UWTM and laser therapy were used alone or in combination. Combined treatment group had the most significant improvements in pain, QOL, and thigh circumference.
D. Physiological & Cardiovascular Effects
Changes in physiological parameters in healthy dogs on an underwater treadmill when the water level is set at the hip joint, by Miyata et al. (2023)
Heart rate and blood lactate increased significantly during 20 minutes of UWTM exercise. Other values remained stable. The data suggest UWTM creates a measurable but safe cardiovascular and metabolic load.
Physiological effects of water temperatures in swimming toy breed dogs, by Nganvongpanit et al. (2014)
Dogs swam at 25°C, 33°C, and 37°C. HR and RR were highest at temperature extremes. 33°C provided the most balanced physiological response and is recommended for safety.
Physiological effects of land and water treadmill exercise in dogs, by Fernandes et al. (2022)
Fernandes et al. (2022) compared the physiological effects of incremental exercise on land and underwater treadmills in healthy dogs. Respiratory rate was significantly lower after underwater treadmill exercise, indicating greater respiratory effort and control. Other parameters, including heart rate, blood pressure, and lactate, showed no significant difference between modalities. Both exercises were safe and aerobic, but UWTM imposed a greater physiological load.
Conclusion
The growing body of hydrotherapy research brings us closer to developing precise, evidence-based protocols. While much progress has been made in understanding how water depth, movement, and equipment influence musculoskeletal and cardiovascular outcomes, large-scale and condition-specific studies are still needed. As practitioners, we are in a unique position to drive this research forward. Every swim, stride, and submerged step holds the potential to shape the future of canine rehabilitation.
References
- Bliss, C., & Terry, J. (2023). Limbs kinematics of dogs exercising at different water levels on the underwater treadmill.
- Miyata, K., Kuroda, T., & Watanabe, K. (2023). Changes in physiological parameters in healthy dogs on an underwater treadmill when the water level is set at the hip joint.
- Hodgson, K., Blake, R., & de Godoy, R. (2023). A study using a canine hydrotherapy treadmill at five different conditions to kinematically assess range of motion of the thoracolumbar spine in dogs.
- Pérez, M.R., et al. (2022). A novel statistical approach to evaluate the effectiveness of physical rehabilitation in dogs with hip osteoarthritis.
- Seychell, E., & Tabor, G. (2022). Forelimb kinematics of healthy dogs at different water depths on a treadmill.
- Fernandes, A.R.F., et al. (2022). Physiological comparison between walking on land treadmill and underwater treadmill in healthy dogs.
- Mojarradi, A., et al. (2021). Safety of early postoperative hydrotherapy in dogs undergoing thoracolumbar hemilaminectomy.
- Fisher, C.J., et al. (2021). Effects of a floatation vest and water flow rate on limb kinematics of Siberian huskies swimming against a current.
- Vitger, A.D., et al. (2021). The impact of water depth and speed on muscle fibre activation of healthy dogs walking in a water treadmill.
- De Oliveira Reusing, M.S., et al. (2021). Effects of hydrotherapy and low level laser therapy in canine hip dysplasia.
- Birch, E., & Simms, R. (2021). A comparison of apparent neck and back angles before, during and after canine hydrotherapy.
- Preston, T., & Wills, A.P. A single hydrotherapy session increases range of motion and stride length in Labrador retrievers diagnosed with elbow dysplasia.
- O’Rourke, S., & Wills, A.P. A comparison of stride parameters and carpal and tarsal joint angles during terrestrial and swimming locomotion in domestic dogs.
- Fish, F.E., et al. The ‘dog paddle’: Stereotypic swimming gait pattern in different dog breeds.
- Bertocci, G., et al. (2020). Aquatic treadmill water level influence on pelvic limb kinematics in cranial cruciate ligament-deficient dogs with surgically stabilised stifles.
- Parkinson, S., et al. (2018). Effect of water depth on muscle activity of dogs when walking on a water treadmill.
- Barnicoat, F., & Wills, A.P. (2016). The effect of water depth on limb kinematics of the domestic dog during underwater treadmill exercise.
- Levine, D., et al. (2010). Effects of partial immersion in water on vertical ground reaction forces and weight distribution in dogs.
- Marsolais, G.S., et al. (2003). Kinematic analysis of the hind limb during swimming and walking in healthy dogs and dogs with surgically corrected cranial cruciate ligament rupture.
- Nganvongpanit, K., et al. Physiological effects of water temperatures in swimming toy breed dogs.
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