Abstract

The effects of prolonged exercise at 65 - 70 VO2max were examined in seven highly trained females. The subjects, aged 22-35 years, underwent an initial incremental treadmill test to exhaustion, with assessment of VO2max and related cardiorespiratory variables. One week later subjects ran at approximately 65 VO2max for 80 min on a motor-driven treadmill. Venous blood was analyzed for glucose, lactate, osmolality, Na, K, protein, and hemoglobin (Hb). Hematocrit was measured and changes in plasma volume calculated. VO2, VE, respiratory exchange ratio, and heart rate were recorded at 17, 37, and 77 min. The percent body fat estimated from skinfold thicknesses was 19 +/- 1 . The mean VO2max was 59.3 +/- 1.0 ml/kg/min, with a mean max VE STPD and heart rate of 78.75 +/- 3.10 l/min and 175 +/-4 beats/min, respectively. No significant changes occurred in VO2, VE, VO2max, heart rate, venous lactate, plasma glucose, or plasma protein during the prolonged exercise. A significant decrease in respiratory exchange ratio was noted. Significant changes also occurred in hematocrit, Hb, Na, K, and osmolality. An interesting finding was the pre-exercise expansion of the plasma volume. Verf.-Referat