Optimizing bone growth to reduce equine fracture

Included in the Grayson-Jockey Club Research Foundation's 2021 funded research, www.grayson-jo..., is a project from Dr. Mariana Kersh, University of Illinois Urbana-Champaign.
Musculoskeletal injuries, especially fractures to the lower leg, are a major reason for racehorse injury and are expensive to fix, but may be minimized using exercise to encourage bone adaptation. These fractures may be reduced by introducing an exercise intervention strategy in young horses to strengthen their bones.
This project will identify how exercise-related biomechanical changes in young foals can lead to optimal bone adaptation and decreased fracture risk. By using a combination of imaging, mechanical testing, and computer modeling, the project provides a molecules-to-bone scale understanding of bone modeling and remodeling to improve bone strength.
The objective of the current proposal is to (1) evaluate two exercise interventions that use different speeds (12 foals) and (2) identify markers (biomechanical and biological) of bone activity that can be used to predict adaptation to exercise. We hypothesize that a constant speed exercise regimen will produce similar bone adaptation compared to an increasing speed exercise regimen. Musculoskeletal simulations will be used to predict muscle and joint reaction loads on the bones, to be used in predictions of bone strength. Two exercise protocols will be implemented in a separate set of foals from ages 8-16 weeks. Intervention 1 will consist of ten minutes of daily exercise at a constant speed (measured via accelerometers). Intervention 2 will consist of a gradual increase in speed over the 8 weeks. We hypothesize that the greatest bone response to exercise for mid-shaft cross-sectional properties (total area, cortical area, etc.) will occur before the epiphyseal growth plate fuses. Additionally, we hypothesize that cross-sectional properties that resist bending loads in the cannon and compressive loads in the long pastern should increase with positive allometry (changes in proportion due to growth). The results of this study will provide a thorough rationale for how muscle and joint forces load bone during movement, and provide evidence of the efficacy of exercise intervention during growth, which may be translated to other species
Importance to the Equine Industry: Horse breeders need an easy-to-follow exercise intervention strategy that has proven effective, if it is to be adopted and used. The fetlock is the location of the most distal limb fractures in racehorses. Characterization of normal growth and development of the cannon and long pastern bones is the first step in understanding the effects of early age exercise on bone health. Priming the bones during growth may cause them to strengthen in areas of common fracture. Using finite-element models will allow us to understand bone growth and development without the need to sacrifice foals. Validation of an exercise intervention that is easy to implement would increase the likelihood of its adoption by racehorse breeders.