The effect of exercise on pro-inflammatory cytokine expression in the young racehorse and its impact on training-related injuries.

Exercise-associated injuries are the most common cause of total days lost from training in 2 and 3 yr old Thoroughbred racehorses. While the reasons and causes of these injuries are varied, inflammation is thought to play a central role. Pro-inflammatory cytokines are induced by vigorous exercise and can be associated with the mild symptoms of delayed-onset muscle soreness to debilitating problems related to soft tissue, joint and bone damage. While there is a great deal of information available on cytokine changes in response to different modes and intensities of exercise in humans, there has been limited work of this nature done in horses. In general, equine athletes exhibit evidence of increased inflammatory cytokine expression subsequent to exercise, though most of this work is from treadmillbased exercise studies. Here we propose to assess the effect of exercise on pro-inflammatory cytokine gene expression in a group of young Thoroughbreds undergoing race training. Our hypothesis is that the expression of pro-inflammatory and other genes in peripheral blood cells can be used to identify horses at risk for training-related injuries. Our approach will be to assess the effect of exercise and training on gene expression in these horses and to compare these results with the occurrence and frequency of training-related injury in this same population. Peripheral blood samples will be collected prior to exercise and three hours later in order to measure pro-inflammatory cytokine and other genes expression. Preliminary data has shown that we will be able to detect specific changes in gene expression at these time points. We will then periodically resample the same as they go through their training program. Since adaptation to exercise leads to reduced inflammatory responses in trained human athletes, we expect to see a similar decrease in the response as the horses are successfully trained. However, increased production of pro-inflammatory cytokines post-exercise could occur, especially in those horses at risk for injury. Our ultimate goal will be to compare these measures of inflammation during training with the ultimate performance of the horses in the training program. Thus, we will compare our cytokine results with data regarding training-related injury or lost training time (wastage) for these same horses. This may allow us to identify any changes in gene expression that could serve as a predictor for training-related injury.