High-intensity exercise induces structural, compositional and metabolic changes in cuboidal bones–findings from an equine athlete model.

This research study examined the effects of intensive exercise on the cuboidal bones of racehorses. The research team hypothesized that racehorses would exhibit an increase in the mineral composition of these bones and changes in the collagenous matrix and bone formation markers. The study showed a net increase in bone formation, bone collagen synthesis, and bone remodeling in racehorses. However, it also revealed a potential risk of failure of the denser, more rigid cortical bone due to its unsupported, rapidly remodeled, and structurally weakened underlying trabecular bone.

Research objective and hypothesis

• The study aims to investigate the impact of high-intensity exercise on the structural, compositional, and metabolic changes in cuboidal bones using an equine athlete model.
• Scientists hypothesized that racehorses would show an increase in the mineral component of these particular bones, post-translational modifications of the collagenous matrix, and changes in markers indicating collagen remodeling and bone formation.

Study design and methodology

• The research studied the third (C(3)) and radial (C(r)) carpal bones from both raced and non-raced Thoroughbred (TB) horses.
• The team retrieved standardized samples from the bones, which were then transversely sliced to study differences in bone metabolism, ranging from the subchondral plate to the trabecular bone.
• Alongside histomorphometry and bone mineral density measurements, biochemical analyses were conducted, including examination of total collagen, collagen synthesis and cross-links, matrix metalloproteinases-2 and 9 and their inhibitors, calcium and phosphate, and bone alkaline phosphatase.

Results and findings

• The results showed an overall increase in bone formation, bone collagen synthesis, and remodeling in the racehorses, especially within the trabecular regions of the bone.
• Increased bone density could result in higher stiffness, particularly in the cortical bone.
• The cortical bone’s increased density and stiffness potentially expose it to the risk of failure, mainly due to a lack of support from the underlying trabecular bone, which is rapidly remodeling and structurally weakened.