Effect of exercise on age-related changes in collagen fibril diameter distributions in the common digital extensor tendons of young horses.

This study investigates whether high-intensity treadmill exercise could impact the size of collagen fibrils found in a specific tendon of young horses. It concluded that age appears to reduce the size of these fibrils, but exercise does not have a significant influence.

Study Design and Methodology

• The researchers studied 24 female Thoroughbreds.
• The horses were divided into two training groups: one group trained for 18 weeks (short term), and the other group trained for 18 months (long term). Both groups used a high-speed treadmill for their training.
• Two control groups, matched for age with the training groups, were used for comparison. These horses only performed walking exercises.
• Collagen samples were taken from a specific tendon on the horses’ forelimbs, known as the common digital extensor tendon (CDET), after the completion of the training programs.
• At least 1,000 collagen fibrils from each sample were analyzed through transmission electron microscopy.
• Using computerized image analysis, the diameter and area of these fibrils were calculated.
• The mean average diameter (MAD) of the collagen fibrils was calculated for each horse and used for comparison.

Key Findings

• The study found that the collagen fibril MAD was smaller in older horses compared to younger ones.
• No significant impact of exercise on fibril size or distribution was found in either the younger or older groups.
• The collagen fibril index, a measure which gives a further understanding of the collagen structure, was not significantly different between the groups.

Conclusions and Implications

• The study’s results align with previous findings suggesting that age can lead to a reduction in collagen fibril MAD.
• In contrast to some past research, this study did not find that training and exercise lead to a decrease in collagen fibril MAD. This finding might highlight some unknown differences in how various types of tendons respond to exercise.
• The findings lend support to an existing theory that different tendons in horses have unique reactions to high-intensity workout programs. It seems the CDET and another tendon known as the superficial digital flexor have fundamentally different responses.