Blood-gas tensions and acid-base status in ponies during treadmill exercise.

The study describes how certain blood properties in ponies change in response to varying intensities of treadmill exercise. It found that heavier exercise leads to increased blood hemoglobin concentration, decreased carbon dioxide levels indicating hyperventilation, and a marked onset of metabolic acidosis demonstrating by increased lactic acid concentration.

Method and Subjects

• In this study, the researchers took readings from 8 healthy, normal ponies. These measurements were performed both when the ponies were at rest and during varying intensities of treadmill exercise.

Exercise Intensity and Heart Rate

• The researchers laid out two intensities: moderate and severe exercise. These were denoted by a fast trot and gallop, respectively.
• They took note of the heart rates for each level of intensity, with averages of 155 beats/min for moderate exercise and 218 beats/min for severe exercise.

Oxygen Measures

• The arterial oxygen tension and hemoglobin-oxygen saturation didn’t change from the resting values under any level of intensity.
• However, the arterial oxygen content increased significantly as the intensity of the exercise increased. This was due to an increase in hemoglobin concentration in the blood, which is the protein in red blood cells that carries oxygen.
• The total oxygen content and the saturation of hemoglobin with oxygen in mixed venous blood both decreased at each intensity of exercise.

Carbon Dioxide and Metabolic Acidosis

• The arterial carbon dioxide tension also decreased with both moderate and severe exercise. A decrease in carbon dioxide level may indicate hyperventilation, where the pony breathes faster and more deeply than usual.
• During severe exercise at a steady state, especially when the ponies were galloping, there was a marked metabolic acidosis. Metabolic acidosis is a condition characterized by too much acid in the body fluids.
• The metabolic acidosis was indicated by a sharp increase in the concentration of lactic acid in the pony’s arteries, with the levels being significantly higher during severe exercise compared to at rest.
• This higher lactic acid concentration was coupled with a decrease in arterial pH and bicarbonate concentration, further indicating the onset of metabolic acidosis.