Plasma volume changes and cardiovascular responses associated with weight lifting.

Ten experienced weight lifters were studied to determine the influence of strenuous, free-weight, squat lift exercise on changes in plasma volume, mean arterial pressure, and the rate pressure product. After a 40-min postural adjustment prior to upright exercise, each subject completed eight sets of eight repetitions of the squat exercise at 55% of the one-repetition maximum. Electrocardiogram heart rate was monitored throughout the test, and blood pressure was determined at the completion of each exercise set. Arterialized capillary blood was drawn during sitting and standing pre-exercise and at the end of the second, fourth, sixth, and eighth sets for the measurement of hemoglobin, hematocrit, and plasma protein concentration, and after the last set for blood lactate. Five additional subjects participated in a postural control comparison. The results of the ANOVA showed a significant loss in plasma volume over the trials which was 2 1/2 times greater than for the control subjects (17.9 vs 7.7% loss) over the same period of time. Exercise rate pressure product increased by 2.85 times resting while only 1.1 times resting for the control subjects. An elevation in mean arterial pressure was found to be correlated to changes in plasma volume, r = -0.98. This study found that plasma volume is reduced while the rate pressure product is increased during the squat lift exercise.