Water depth and speed may have an opposite effect on the trunk vertical displacement in horses trotting on a water treadmill.

The research examines the different impacts of water depth and speed on how much a horse’s trunk moves up and down while trotting on a water treadmill. The study demonstrated that deeper water and slower speeds lead to an increase in vertical displacement, whereas higher speeds led to a decrease.

Study Design and Implementation

• The study involved six healthy Standardbred horses, with a median age of 12 years, who were made to trot on a water treadmill. The treadmill was used in different conditions, including dry (no water), and with water levels at the mid-cannon, mid-radius, and shoulder of the horses.
• The horses trotted at two different speeds: 3.5 meters per second and 5 meters per second.
• Accelerometers placed at the withers, the thoracolumbar junction (T18), tuber sacrale (TS), and at the sacrum (S5) of the horses measured their dorsoventral movement, which is essentially the up and down movement of the trunk with each stride.

Results

• When the horses trotted in water at depths mid-cannon and mid-radius, the upward and downward excursion of their trunk was greater than when they trotted on a dry treadmill, most significantly at the mid-radius level and at the thoracolumbar junction (T18).
• The study also found that when trot speed was increased from 3.5 to 5 meters per second, the vertical displacement at T18 reduced across all water levels, and at the mid-radius water level for the withers and TS.

Conclusion

• This research concluded that both the water depth and trotting speed influences the vertical displacement of the horse’s trunk while trotting on a water treadmill, but in opposing ways.
• Specifically, the movement of the horse’s trunk increases when the water level is increased up to mid-radius, but decreases with an increase in trotting speed, with the most pronounced effects at the thoracolumbar junction.