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

## TL;DR

This study shows that circular exercise in juvenile sheep affects bone health, with speed and circle size influencing bone formation and strength.

## Contribution

The study introduces a novel equine model using juvenile sheep to evaluate how circular exercise impacts musculoskeletal health.

## Key findings

- Faster exercise speeds increased bone formation and reduced resorption in juvenile sheep.
- Large circles at fast speeds improved bone strength in the outside leg compared to the inside leg.
- Small circles at slow speeds increased bone density in the outside leg, while the opposite occurred in large circles at slow speeds.

## Abstract

Circular exercise is a common practice in many disciplines, whether it be in the form of lunging, a mechanical walker, or ridden exercise. However, how horses adapt to circular exercise may put their bone and joint health at risk. To evaluate how the musculoskeletal system responds to circular exercise, juvenile sheep were used as a model for young horses. Circular exercise was found to influence traits of bone quality, including density and fracture force. Speed and circle diameter also influenced markers of bone formation and bone resorption. Though no joint damage was found, it is possible that joint changes were undetected and tighter or faster circles would have produced different results. It is important for one to consider factors such as speed and circle diameter in their exercise programs to help ensure the musculoskeletal health of equine athletes.

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 (p < 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 (p < 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 (p < 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.