Objective: To determine the effects of a dose of caffeine (2.5 mg/kg, IV) administered to physically fit Thoroughbreds during incremental exercise testing to fatigue on a treadmill.
Animals: 10 conditioned Thoroughbreds.
Procedure: Horses were randomly assigned to receive caffeine or a control solution. Each horse received both treatments in a crossover design with a 3-week interval between treatments. Each horse was administered caffeine (2.5 mg/kg) or an equivalent amount of a control solution IV. One hour after injection, each horse performed an incremental exercise test to exhaustion. Hematologic values, heart rate, oxygen consumption, carbon dioxide production, plasma lactate concentration, urine and serum concentrations of caffeine and metabolites, and time until exhaustion were monitored. Statistical analysis was performed by use of a mixed-effects linear model.
Results: Significant differences in measured values when horses were treated with caffeine or the control solution were not detected.
Conclusions and clinical relevance: A dose of caffeine (2.5 mg/kg, IV) appears to have no effect on any performance variable of physically fit Thoroughbreds during incremental exercise testing to fatigue.