Abstract
Increases in blood viscosity during various kinds of strenuous exercise have been repeatedly described. In this study we investigated the rheologic effects of long duration low intensity exercise. Twelve volunteers (21–39 yr, 6 men and 6 women), after overnight fasting, performed a 60min exercise on cycloergometer at 55% of the theoretical maximal heart rate. After an early increase at the 10th minute (p<0.001), blood lactate decreases (p<0.02) and returns to normal. During exercise there is an increase in plasma viscosity (p<0.001) and hematocrit (p<0.05) at the 10th minute. Red cell rigidity index “Tk” increases at the 20th minute (p<0.05). Whole blood viscosity (p<0.01) increases and hematocrit/viscosity ratio decreases (p<0.01). Thus, a light prolonged work load induces a transient hyperviscosity pattern very similar to that which is observed during strenuous exercise bouts.
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