Biochemical markers of bone activity in young standardbred horses during different types of exercise and training.

The purpose of this research was to understand the impact of varying intensities of exercise on bone metabolism in young Standardbred horses over a six-week training program. The investigation included specific biochemical markers related to bone activity and observed changes in their concentration levels.

Training Program and Exercise Testing

• The chosen test subjects were seven young, untrained Standardbred horses. The horses were put through a six-week training program that included both high-speed and low-speed exercises. These exercises were performed on a treadmill.
• The initial exercise tests, known as Standard Exercise Test 1 (SET 1), were six incremental exercises each lasting 5 minutes, with speeds starting at 5 m/s and increasing by 1 m/s each step.
• After SET 1, the six-week training program started with alternating high-speed exercise (HSE) for 15 minutes and low-speed exercise (LSE) that lasts for 60-90 minutes. The HSE continuously increased in speed every 60 seconds by 0.3 m/s, whereas the LSE was constant velocity.
• The training program was followed by Standard Exercise Test 2 (SET 2) and a deconditioning period of 12 weeks.

Biomarkers Investigated and Observations

• Throughout the experiment, the researchers collected blood samples from the horses to study lactate, total plasma protein (TPP), osteocalcin, and ICTP (cross-linked C-telopeptide of type I collagen), all of which are indicators of bone metabolic activity.
• ICTP levels rose during SET 1 and SET 2 and also after both the first and last LSE, demonstrating a significant increase due to exercise. Osteocalcin, another bone marker, decreased to below resting levels 24 hours after SET 1.
• No significant changes were noted in the level of osteocalcin during the first LSE, but 24 hours after this exercise, osteocalcin levels dropped below pre-exercise levels. After the eighth LSE, osteocalcin increased and then reduced 24 hours afterwards.
• In contrast, no changes were noted in osteocalcin and ICTP levels after HSE, indicating that the intensity of exercises matters in bone metabolism.
• Researchers found that baseline levels of osteocalcin dropped throughout the training program, showing a longer-term effect of regular exercise on this particular biomarker.

Conclusion

• The study concluded that the immediate response of biochemical bone markers indicated the direct influence of a single bout of exercise on bone metabolism. This conclusion provides vital insights into bone health and the importance of exercise intensity in young Standardbred horses.