The Effect of Furosemide-Induced Hypohydration on the Athletic Performance of Standardbred Horses
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Furosemide is a potent diuretic commonly administered to racehorses in an attempt to prevent exercise-induced pulmonary hemorrhage (EIPH). However, recent studies suggest that furosemide administration may have performance-enhancing effects aside from its effects on EIPH. This study examined the effect of furosemide-induced hypohydration on the athletic performance of four Standardbred horses. Each horse received one of three treatments: 1) no furosemide (control); 2) IV injection of 1 mg/kg furosemide 4h pre-exercise (mild hypohydration); 3) IV injection of 1 mg/kg furosemide 4h pre-exercise followed by a second IV injection of I mg/kg furosemide 2h pre-exercise (moderate hypohydration). Exercise was performed on a treadmill at a constant speed of 13 m/s until the onset of fatigue. Furosemide-induced mild and moderate hypohydration produced significantly different body weight reductions of 2.78% ± 0.12 and 3.39% ± 0.40, respectively. We observed an 8.4% and 7.8% decrease in run time with mild and moderate hypohydration, respectively, however these differences were not statistically significant. Analysis of physiological factors in response to exercise and during recovery did not suggest that furosemide administration contributed to the onset of fatigue. We concluded that the levels of hypohydration investigated in this study had no deleterious effects on athletic performance. Furthermore, our findings, combined with previous research, allow for the possibility that furosemide administration prior to racing many enhance performance through its body weight reducing effects.