The response of bone, articular cartilage and tendon to exercise in the horse

Abstract

Horses can gallop within hours of birth, and may begin training for athletic competition while still growing. This review cites studies on the effects of exercise on bone, tendon and articular cartilage, as detected by clinical and research imaging techniques, tissue biochemical analysis and microscopy of various kinds. For bone, alterations in bone mineral content, mineral density and the morphology of the mineralized tissue are the most common endpoints. Apparent bone density increases slightly after athletic training in the cortex, but substantially in the major load paths of the epiphyses and cuboidal bones, despite the lower material density of the new bone, which is deposited subperiosteally and on internal surfaces without prior osteoclastic resorption. With training of greater intensity, adaptive change is supervened by patho-anatomical change in the form of microdamage and frank lesions. In tendon, collagen fibril diameter distribution changes significantly during growth, but not after early training. The exact amount and type of protracted training that does cause reduction in mass average diameter (an early sign of progressive microdamage) have not been defined. Training is associated with an increase in the cross-sectional area of some tendons, possibly owing to slightly greater water content of non-collagenous or newly synthesized matrix. Early training may be associated with greater thickness of hyaline but not calcified articular cartilage, at least in some sites. The age at which adaptation of cartilage to biomechanical influences can occur may thus extend beyond very early life. However, cartilage appears to be the most susceptible of the three tissues to pathological alteration. The effect of training exercise on the anatomical or patho-anatomical features of connective tissue structures is affected by the timing, type and amount of natural or imposed exercise during growth and development which precedes the training.

Effect of loading on the organization of the collagen fibril network in juvenile equine articular cartilage

“…The future susceptibility to injury could potentially be influenced by means of well-tailored exercise regimens, which will be of most interest in those species (human, horse) in which longterm orthopedic health is a serious concern. 13,30 Having shown that even mild exercise influenced structural and biochemical characteristics positively, it is unclear if this type of manipulation is beneficial in the long-term. Exposure to the challenges that will be faced during an athletic or working career at a young age, when collagen configuration is still being shaped, may positively influence provision of the type of collagen that is best adapted and, hence, least susceptible to injury.…”

Comparison of the Proximal Phalanx Parameters in Warmblood and Coldblood Horses with the Use of Peripheral Quantitative Computed Tomography

“…This phenomenon can be explained by no significant differences regarding the cortical thickness between pastern bones of W and C horses, whose proximal phalanges are subjected to other forces and strains. Some scientists studying the bone remodelling phenomenon, also in literature known as "bone turnover", observed that there are differences in the proportions between the trabecular bone (trabecular area) and the cortical bone (cortical area) in the distal sesamoid bone of various types or breeds of horses (7,15,20). It was found that W horses possess larger amounts of trabecular bone but less cortical bone in comparision to C horses (15).…”

“…In horses, bone modelling process was observed (7,15,20). The phenomenon of modelling the bones, especially the distal segment of thoracic limbs, has been described in details (15).…”

The cross-sectional area of the superficial digital flexor tendon of trained and untrained Thoroughbred racehorses

“…The significance of this is that athletic training results in progressive changes in the molecular and cellular components of the flexor tendons (BIRCH et al, 1999;CHERDCHUTHAM et al, 2001;FIRTH, 2006). Training is a factor that results in adaptive hypertrophic changes in the matrix composition of the tendons, resulting in an increase in CSA, which may remain through the horse's life, (BIRCH et al, 1999;CHERDCHUTHAM et al, 2001).…”