Renal and systemic hemodynamic responses to sustained submaximal exertion in horses.

This research study explores how an hour of moderate exercise impacts the kidney and overall blood flow in horses. The findings suggest that horses can maintain normal kidney function and overall blood circulation, despite increased blood concentration and body temperature during sustained moderate exercise.

Research Methodology and Design

• In this research, the response of six horses to 1 hour of sustained submaximal exertion was studied. The horses were made to run on a treadmill at a speed that maintained their heart rate at 55-60% of the maximum for each creature. This approach ensured that the exercise was severe enough to test the cardiovascular response but gentle enough not to be damaging.
• Specific parameters measured included heart rates, cardiac output, kidney function (measured by p-aminohippuric acid and creatinine clearances), filtration fraction, and renal blood flow. Other variables considered were the plasma total solid concentration, hematocrit (the proportion of blood made up of red blood cells), and body temperature (measured via the pulmonary artery).

Research Findings

• During the sustained exercise, heart rates increased from an average of 121 beats/min after 15 minutes of exertion to 126 beats/min after a full hour of exertion.
• Cardiac output (the volume of blood the heart is pumping) increased significantly in the first 15 minutes of exertion, but then stabilized, indicating the body’s ability to adapt to the increased physical demand.
• Kidney function, as measured by creatinine and p-aminohippuric acid clearances, showed no significant change from rest throughout the period of exercise. The same was observed for the filtration fraction (the proportion of blood filtered by the kidneys) and renal blood flow.
• Both plasma total solid concentration and hematocrit increased between the 20-minute mark and the end of the hour of exercise. This hemoconcentration indicates an increased concentration of cells and solids in the blood due to fluid loss, and can be seen as a measure of dehydration.
• Body temperature significantly increased from a resting level of 37.6 degrees Celsius to reaching 38.6 degrees Celsius after 60 minutes of exertion.

Conclusion

• The major takeaway from this research is that horses can maintain normal kidney and systemic blood flow dynamics even during sustained periods of suboptimal exercise. This is despite the hemoconcentration and increased body temperature observed during the period of exertion.