Effects of treadmill exercise on cortical bone in the third metacarpus of young horses.

The research study investigates how exercise, particularly treadmill exercise, affects the cortical bone in the metacarpal (forelimb) of young horses, comparing exercised horses with those that are unexercised.

Methodology

• The study used two groups of horses; one group was subjected to a 14-week exercise program (n=6), and the other group was held as unexercised controls (n=6).
• The exercise program involved a variety of exercises ranging from trots to canters, carried out on a treadmill set at a 3 degrees incline. The training intensity and speed were gradually increased over the course of the weeks.
• After the exercise regimen, the cortical bone condition of the horses was assessed in various ways including through histomorphometric analysis, microradiography, and measuring the bone mineral content.

Findings

• The exercise resulted in substantial differences in the cortical porosity (degree of small holes in the bone) and the distribution of subperiosteal osteogenesis (formation of new bone tissue under the outer layer of the bone) at the mid-shaft of the third metacarpal.
• There was minimal bone remodeling in the exercised horses, as shown by less bone turnover, but extensive new bone formation as evidenced by a larger amount of subperiosteal bone formation.
• In contrast, the unexercised horses had more evidence of bone remodeling and less formation of new subperiosteal bone.
• The bone mineral content, a critical measure of bone health, increased more in the exercised horses than in the unexercised, despite having a lower overall growth in body weight.
• The speed of ultrasound through the bone, a measure that encapsulates several aspects of bone quality, including porosity and the amount of new bone formation, increased significantly by the end of the training period in the exercised horses.
• The unexercised horses remained largely unchanged in this measurement, showing a smaller increase, reflecting differences in the intracortical bone porosity, endosteal bone formation, and changes in skin thickness between the two groups.
• The stiffness of the cortical bone, an essential factor for the strength and resilience of the bone, also significantly increased in the exercised horses but remained unaltered in the unexercised horses.

Conclusion

• The research provides evidence that exercise, specifically structured treadmill sessions, has a profound impact on cortical bone health in young horses.
• Exercise causes less bone remodeling but more new bone formation under the periosteum (outer layer of the bone).
• These changes in bone structure lead to an increase in bone mineral content and improved bone quality, as measured by ultrasound speed, in exercised horses.
• These improvements in bone health have implications for the overall health of young horses and may help prevent bone-related injuries and diseases in the future.