Plasma potassium and lactate concentrations in thoroughbred horses during exercise of varying intensity.
To investigate the effect of moderate to high intensity exercise of up to 6 min duration on plasma potassium and lactate concentrations, 6 Thoroughbred horses were studied using a treadmill at a 5 degree incline. Each test consisted of an 8-min standardised warm-up followed by an exercise bout at 8, 9, 10 or 12 m/sec. The horses were galloped at each speed for up to a maximum of 6 min or until signs of fatigue were present. The horses were then walked at 0 degree incline. Carotid arterial blood samples were taken during and after the exercise. At 8, 9 and 10 m/sec there was a general pattern of an initial rise in potassium to a peak around 1.5 min of exercise with the concentration then slowly decreasing. At 12 m/sec there was a continuous rise to a peak at the end of exercise in all horses. Immediately after exercise there was a rapid return (within 3-4 min) to the potassium concentrations recorded at the end of the warm-up period. Plasma lactate peaked around the end of exercise at all speeds. At the highest intensity of exercise the mechanisms for the re-uptake of potassium did not appear to be able to match the rate of efflux. In contrast, at less intense work loads, the rate of re-uptake appeared to be similar to or slightly greater than the rate of efflux. It is possible that a disturbance in this balance between efflux and re-uptake could result in a disturbance in normal neuromuscular function during exercise.
Harris
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Animal Health Trust, Newmarket, Suffolk, UK.
Snow
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DH
D000136:Acid-Base Equilibrium; D000818:Animals; D001798:Blood Proteins / Q000032:analysis; D005080:Exercise Test / Q000662:veterinary; D005260:Female; D006339:Heart Rate; D006400:Hematocrit / Q000662:veterinary; D006736:Horses / Q000097:blood* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000097:blood*; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D011188:Potassium / Q000097:blood*
D001798:Blood Proteins; D007773:Lactates; D011188:Potassium