Manufacturers initially developed equine water treadmills for rehabilitation, but over the years they’ve gained popularity for conditioning horses. Despite their increased use, little research exists documenting how water treadmills affect horse fitness. And the research that does exist doesn’t support specific exercise intensity and duration for training.

To investigate, a team from the University of Calgary and Washington State University schools of veterinary medicine set up a study in which they evaluated fitness in horses trained both on treadmills with and without water. Canadian student Persephone Greco-Otto, who’s currently pursuing a doctoral degree in veterinary medical science, presented the team’s results at the 2017 American Association of Equine Practitioners Convention, held Nov. 17-21 in San Antonio, Texas.

Water treadmills have a revolving belt that horses walk (or trot) on in an encasement that seals and fills with water. The water adds resistance, increasing exercise intensity without increasing the belt speed or incline.

The randomized, controlled trial included nine unfit Thoroughbreds. The horses participated in a pre- and post-conditioning maximal-exercise racetrack test, which recorded their:

  • VO2max (the maximum amount of oxygen an individual uses during intense, or maximal, exercise; the best measure of skeletal muscle aerobic capacity and cardiovascular fitness);
  • Ventilation, including respiratory frequency, tidal volume (the amount of air which enters the lungs during normal inhalation at rest), minute ventilation (the amount of gas inhaled or exhaled during one minute;
  • Heart rate;
  • Whole blood lactate; and
  • Speed.

After the researchers recorded pre-conditioning scores in all nine horses, they started three control horses in an exercise program on a treadmill without water (the dry treadmill, or “DT”) and six on the water treadmill (“WT”), with water height set at the horses’ stifles. The program included daily exercise at the walk (1.45 meters per second, or 3.24 miles per hour) for 20 minutes over an 18-day period.

At the exercise program’s conclusion, the researchers retested all nine horses on the racetrack. Neither maximum heart rate nor maximum speed changed for the study horses from the initial to final fitness testing, Greco-Otto said. However, the WT-conditioned horses showed a 16% increase in their VO2max and a 17.4% increase in average speed. Horses in the DT-conditioned group didn’t exhibit significant increases in fitness.

Despite the relatively low-intensity nature of WT exercises, a protocol using water at horse stifle height significantly increased V̇O2max and endurance in Thoroughbreds, Greco-Otto said.

“Adding WT protocols to the training program of horses may have a beneficial conditioning effect, while minimizing concussive forces,” she noted.