Effects of Exercise Speed and Circle Diameter on Markers of Bone and Joint Health in Juvenile Sheep as an Equine Model.

Though circular exercise is commonly used in equestrian disciplines, it may be at the detriment of horses' musculoskeletal system. To investigate the effects of circular exercise on bone and joint health, 42 lambs were randomly assigned to a non-exercised control, straight-line, small circle, or large circle exercise regime at a slow (1.3 m/s) or fast (2.0 m/s) speed for 12 wk. Blood samples were taken biweekly. Animals were humanely euthanized upon study completion, and the fused third and fourth metacarpals were collected for biomechanical testing and bone density analysis. Fast groups were found to have more bone formation and less resorption activity than slow groups as evidenced by serum biomarker concentrations ( < 0.05). Sheep in the large fast group tended to have greater flexural rigidity and fracture force for the outside leg compared to the inside leg ( < 0.1). Sheep in the small slow group tended to have increased bone mineral density of the outside leg compared to the inside leg, whereas the opposite occurred in the large slow group ( < 0.1). These results provide further evidence for potential asymmetric musculoskeletal adaptations to circular exercise while emphasizing the importance of speed as a positive influence on bone metabolism and strength.