Caffeine is a drug of the group of methylxanthines, substances that stimulate the CNS.1,2 The Association of Racing Commissioners International does not approve of the therapeutic use of caffeine in horses, and when it is found in the urine or other biological fluids, it is classified as a class 2 illegal substance, characterized as doping.1,3 However, because of the natural presence of caffeine in teas, coffees, chocolates, and rations, professionals who are involved in the day-to-day practice of equestrian sports argue that the detection of low blood and urinary concentrations of caffeine in athletic horses can be associated with environmental contaminations and have no effect on the results of equestrian competitions.3 Currently, investigations of caffeine and its interference with athletic performance in aerobic and anaerobic exercises are performed in a systematic manner in humans2,4 as well as horses3,5; most of the studies on horses use the Thoroughbred breed in their experiments.3,5
In humans, the ergogenic effect of caffeine has been described, and there is consensus on its beneficial effects in aerobic and resistance exercises.2 During intense exercise of short duration, however, there is controversy over the improvement of athletic performance after the administration of caffeine.2 In horses, caffeine was reported to improve the response of cardiovascular function as a result of the stimulation of the CNS.5 In contrast, authors of another study3 did not observe effects on cardiorespiratory variables of horses after the administration of caffeine at a dose of 2.5 mg/kg; horses in that study3 underwent an IET following caffeine administration. The objective of the study reported here was to determine the effects of acute administration of caffeine on physiologic variables of Arabian horses during exercise with increasing intensity on a treadmill, by examining metabolic, endocrine, hematologic, and cardiovascular variables.
Incremental exercise test
Galloper treadmill, Sahinco LTDA, Palmital, Brazil.
Sigma Aldrich, St Louis, Mo.
S610, Polar, Port Washington, New York.
Yellow Springs Instrument Co, Yellow Springs, Ohio.
CELM Companhia Equipadora de Laboratorios Modernos, Barueri, Brazil.
DC 510, CELM Companhia Equipadora de Laboratorios Modernos, Barueri, Brazil.
Kit, Labtest Diagnóstica, Lagoa Santa, Brazil.
EDTA, 5.0 mL, Vacutainer BD, Chacara Santo Antonio, Brazil.
Glistab Cat 29, Labtest Diagnóstica, Lagoa Santa, Brazil
Bio 2000, Bioplus, Barueri, Brazil.
Multispeed refrigerated centrifuge PK121R, ALC, Princeton, NJ.
Coat-a-count, Diagnostic Products Corp, Los Angeles, Calif.
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