Serum enzyme changes in endurance-trained horses and performance markers

Abstract

How do serum enzyme profiles correlate with training intensity and performance outcomes in competitive endurance horses? This research examined biochemical markers in 48 Arabian and Arabian-cross horses participating in endurance racing programs over a 12-month training period. Creatine kinase activity increased 3.7-fold following high-intensity training sessions, with peak values reaching 847 ± 234 U/L compared to baseline 229 ± 67 U/L. Aspartate aminotransferase showed delayed elevation peaking at 24 hours post-exercise. Horses completing 160 km competitions demonstrated significantly lower enzyme elevations compared to non-finishers. Strong negative correlation existed between training-induced enzyme responses and race completion times (r = -0.67, p< 0.001). These findings establish reference intervals for exercise-induced enzyme changes and support serum enzyme monitoring as a practical tool for optimizing equine endurance training programs.