Can exercise modulate the maturation of functionally different immature tendons in the horse?

Abstract

Tendons can be considered in two functional groups, those contributing to energetics of locomotion and those acting solely to position the limb. The energy-storing tendons in both human and equine athletes have a high frequency of injury with similar pathophysiology. In previous studies, high-intensity exercise appears to induce a disruption of the matrix rather than functional adaptation in adults. Here we explore the hypothesis that the introduction of controlled exercise during growth would result in an adaptive response without deleterious effects. Young horses were given a controlled exercise program similar to that previously shown to induce matrix changes in energy-storing tendons of skeletally mature animals. The tendons were assessed in relation to mechanical properties, molecular composition, and morphology. Results showed a significant increase in cartilage oligomeric matrix protein (COMP) in the positional tendon but not in the energy-storing tendon. Other matrix properties and mechanical properties were not significantly changed. While the imposition of high-strain-rate exercise in immature horses failed to augment the development of the energy-storing tendon over and above that induced by normal pasture exercise, it did not induce deleterious changes, supporting an earlier introduction of athletic training in horses.adaptation; hypertrophy; cartilage oligomeric matrix protein; biomechanics TENDON OVERUSE INJURIES are not only responsible for considerable loss of athletic potential in both horses (30,35,58) and humans (64), but their prevalence appears to be increasing, with a doubling in Achilles tendinopathy in recent years (26,27,34,37,38). While tendons that link muscle to bone can act merely as force transmitters to position limbs, a specific subgroup of tendons whose function is to store elastic energy contributes to efficient locomotion by acting as springs, while the associated muscle fibers serve primarily to dampen vibrations (1, 59). The Thoroughbred racehorse is a prime example of an elite animal athlete both in terms of evolution and subsequent genetic selection and conditioning. The superficial digital flexor tendon (SDFT) in the horse is an energy-storing tendon with functional and compositional similarities to the Achilles tendon in humans (7). This tendon is highly susceptible to injury, accounting for 93% of all tendon and ligament injuries in a study by Ely et al. (15) and thus can be used as a "natural" model to study tendon development and degeneration (51). The common digital extensor tendon (CDET) in contrast is a good example of a positional tendon analogous to the anterior tibialis in the human (3, 62).Over the last two decades there has been a great increase in the scientific understanding of the response of bone and muscle to mechanical loading. The mechanobiology of tendon, however, is less well understood. Effects of exercise on tendon properties have been studied in various species, including mouse (36), rat (49, 55), rabbit (61), chicken (2), guinea fowl (8), miniatur...

Age at first start and racing career of a cohort of Australian Standardbred horses

“…A number of studies have identified potential benefits of early training on various aspects of development, including increases in subchondral bone mineral density, 25 hyaline cartilage, 26 cartilage matrix proteins in some tendons 27 and a general protective effect on joints 28 . Only one study looked at how early training affects horses once they begin preparation for racing 29 .…”

Immunolocalization of Collagens (I and III) and Cartilage Oligomeric Matrix Protein in the Normal and Injured Equine Superficial Digital Flexor Tendon

“…Previous studies have shown that the COMP level in the equine tendon increases with maturation up to 3 years of age and then levels off and slowly declines [21,22]. In addition, there are studies indicating that physical activity leads to increased COMP levels in the equine tendon [21] as well as a tendon-specific response to exercise [23]. In addition, high levels of COMP have been found in synovial fluid from digital flexor tendon sheaths of horses with tendon pathology [24], indicating release of fragments from tendon matrix.…”

Reduction of Recurrent Tendinitis Scar Using Autologous Mesenchymal Stem Cells Derived from Adipose Tissue from the Base of the Tail in Holsteiner Horses (Equus ferus caballus)

“…The horses in both CG and EG were included in a standardised exercise routine (Kasashima et al, 2008) designed to help regeneration and maturation of damaged tissue. The exercise protocol consisted of four stages, corresponding to the 4 months of the study.…”