Altered Homeostasis of Extracellular Matrix Proteins in Joints of Standardbred Trotters During a Long‐term Training Programme

This study evaluates how strenuous training, age and lameness influence the release of cartilage oligomeric matrix protein (sf‐COMP), aggrecan and collagen type II into synovial fluid in 28 (19.5–40 months) Standardbred trotters (STB), during a long‐term training programme (24 months). All the horses were trained by the same trainer and were healthy on entering the training programme. Synovial fluid (sf) from the left middle carpal joint in each subject was sampled every third month. Enzyme‐linked immunosorbent assay was used to determine the concentrations of sf‐COMP, sf‐aggrecan and sf‐collagen type II. Concentration of sf‐COMP decreased with increasing age and total days of training. The concentration of sf‐COMP was found similarly related to both age and total days of training, so they could not be differentiated. It was also shown that the concentration of collagen type II degradation products increased with total days of training. The study shows that extensive and long‐term training programme induces metabolic changes in articular cartilage exemplified by reduced release and synthesis of COMP. This is most likely due to strenuous training leading to inappropriate load on the articular cartilage.