Water depth modifies back kinematics of horses during water treadmill exercise.
Authors: Nankervis K J, Finney P, Launder L
Journal: Equine veterinary journal
Summary
# Water Depth and Equine Spinal Kinematics: Implications for Rehabilitation Whilst water treadmill exercise is increasingly used in equine rehabilitation, the specific effects of immersion depth on thoracolumbar spine movement remain poorly characterised. Nankervis and colleagues used motion-capture analysis to track spinal flexion-extension range of motion (ROM) and movement patterns in 14 healthy horses walking at 0.8 m/s across four conditions: dry treadmill (control), plus water depths reaching hoof, tarsal joint (mid-depth) and femoropatellar joint levels. Deep water immersion significantly increased thoracolumbar flexion-extension ROM at multiple spinal segments—notably 52% greater flexion at T10 (8.4° versus 5.5°), 42% greater at T13 (8.1° versus 5.7°), and comparable increases at more caudal vertebrae—whilst subtly shifting the neutral posture towards extension cranially and flexion caudally. Pelvic vertical displacement remained unaffected by depth, suggesting the ROM changes reflect true spinal mobility changes rather than compensatory pelvic movement. For practitioners designing rehabilitation protocols, these findings indicate that high-water treadmill work induces a flexed lumbar posture distinct from ground or shallow-water exercise, making it particularly valuable for mobilising thoracolumbar stiffness but potentially requiring caution in horses with certain flexion-intolerant conditions; conversely, shallow-water work may be preferable when controlled extension or neutral positioning is the therapeutic goal.
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Practical Takeaways
- •When using water treadmill for rehabilitation of horses with back or hindlimb pathology, water depth significantly alters spinal kinematics — higher water depths increase thoracolumbar flexion-extension range, which should be considered when designing progressive rehabilitation protocols
- •Shallow water (hoof depth) produces more conservative spinal movement and may be more appropriate for early-stage rehabilitation, while deeper water (high depth) provides greater spinal mobilization for more advanced stages
- •Pelvic stability (vertical displacement) is maintained across water depths, so water depth adjustments can be used to modulate spinal demands without affecting pelvic mechanics
Key Findings
- •Walking at high water depth (femoropatellar joint level) significantly increased flexion-extension range of motion in T10 (8.4° vs 5.5°), T13 (8.1° vs 5.7°), T18 (6.9° vs 5.1°), and L3 (6.4° vs 5.1°) compared to control (hoof depth)
- •High water depth caused cranial thoracic extension and thoracolumbar flexion compared to walking at hoof depth
- •T13 angular motion minimum was significantly lower in high water (-3.0°) than control (0.1°), and L3 angular motion maximum was significantly greater in high water (-1.9°) than control (-4.8°)
- •Pelvic vertical displacement showed no significant association with water depth across all conditions