Exercise-related alterations in crimp morphology in the central regions of superficial digital flexor tendons from young thoroughbreds: a controlled study.

The research article discusses a study which investigates how a particular 18 month exercise program impacts the collagen fibril crimp angle and period length in the core region of the superficial digital flexor tendon in young Thoroughbred horses, and how these changes might be related to tendon injuries often seen in racehorses.

Objective of the study

• The main objective of this research is to understand whether specific forms of exercise cause substantial changes in collagen fibrils, particularly in the crimp angle and period length, within the superficial digital flexor tendon of Thoroughbred horses. The crimp refers to the waveform of the longitudinal arrangement of these collagen fibrils in tendon.

Significance of the crimp angle

• The researchers highlight the significance of the crimp angle by noting that the fibril bundles with a smaller crimp angle tend to fail (or rupture) at lower levels of strain as compared to those with larger crimp angles. In other words, a decrease in crimp angle might indicate a greater risk of tendon injury. This is especially relevant for racehorses, where there’s an observed high occurrence of injury to the mid-metacarpal region of the superficial digital flexor tendon.

Method and Experimental Groups

• The study compares two groups of young Thoroughbreds (approximately 21 months old) — one group subjected to a specific 18 month exercise programme and a control group that doesn’t follow this particular exercise regimen.

Findings of the Study

• The research found that both crimp angle and length were significantly lower in the exercised horses as compared to control horses.
• Among the exercised horses, the crimp angle in the central region was significantly lower than in the peripheral region of the tendon in 4 out of 5 horses studied. Crimp length followed a similar trend in 3 out of 4 horses.
• The crimp angle in the peripheral region was significantly greater for exercised horses versus the controls. This suggests the possibility of a functional adaptation due to difference in mechanical environment between the two tendon regions.

Implications of the Results

• The results support the hypothesis that specific forms of exercise (like galloping) modify the normal age-related changes in crimp morphology in the core of the superficial digital flexor tendon. These modifications are indications of microtrauma and may weaken the tendon’s strength.