Effects of intravenous administration of caffeine on physiologic variables in exercising horses.

The research investigates the effect of injecting caffeine into Arabian horses and how it impacts their athletic performance. They found that caffeine enhanced the horses’ speed and lessened their glucose oxidation during short-term intensive exercise.

Overview of Study Design

• The study involved twelve healthy, adult Arabian horses that have been trained to exercise on a treadmill.
• The researchers utilized a crossover study design where each horse was given both treatments—caffeine through intravenous (IV) administration (5mg/kg) and IV administration of saline solution approximating the same volume.
• The treatment order was randomized and a break of ten days was instituted between each treatment to allow the physiological variables of the horses to return to their normal state.
• Thirty minutes after each treatment, the horses were tested via an incremental exercise test (IET) on a treadmill.

Data Collection and Results

• The researchers collected blood samples from the horses fifteen seconds before the end of each velocity step of the IET. These were tested to determine the blood lactate, blood glucose, plasma cortisol, and plasma insulin concentrations.
• The researchers also recorded heart rates and analyzed other hematologic variables corresponding to the speed increments.
• The results indicated a significant increase in velocities when the horse heart rates reached 180 and 200 beats per minute for the caffeine-treated horses as compared to the control group.
• Velocities corresponding to blood lactate concentrations of 4 and 2 mmol/L significantly decreased for the caffeine-treated horses compared to the control group.

Comparative Analysis and Conclusions

• The insulin levels were reportedly higher in the control group while blood glucose levels were higher in the caffeine-treated horses.
• The cortisol (stress hormone) levels in the horses’ plasma was significantly reduced after caffeine treatment.
• The researchers concluded that injecting caffeine into Arabian horses at a dose of 5mg/kg improved their performance during short, intense exercise.
• Additionally, the intravenous administration of caffeine resulted in a diminished oxidation of glucose in these horses, suggesting changes in metabolic efficiency under the effect of caffeine.