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. (Am J Vet Res 2005;66:569–573)