Relation of plasma volume change to intensity of weight lifting.

To determine the relation of plasma volume change to intensity of weight lifting, blood samples were obtained from 15 males [mean (+/- SD) age = 22.3 +/- 3.2 yr; height = 176.3 +/- 6.9 cm; weight = 73.0 +/- 11.7 kg] before and over a 60-min period following weight lifting at four different intensities [40, 50, 60, and 70% of one-repetition maximum (1-RM)]. Weight lifting consisted of completing three circuits of four exercises (bench press, bent-over row, arm curl, and parallel squat), with 10 repetitions of each exercise performed over a 30-s period followed by 30 s of rest. Mean (+/- SE) oxygen uptakes (VO2) during weight lifting at the four intensities were 1.31 +/- 0.04, 1.50 +/- 0.07, 1.72 +/- 0.07, and 1.86 +/- 0.08 1.min-1, or 33-47% of treadmill-determined VO2max, respectively. Mean (+/- SE) blood lactates were 6.5 +/- 0.5, 8.7 +/- 0.5, 9.4 +/- 0.6, and 12.0 +/- 0.6 mmol.1(-1), respectively. Mean (+/- SE) heart rates (HR) were 124 +/- 4, 134 +/- 4, 148 +/- 5, and 161 +/- 4 bpm, or 63-82% of treadmill-determined HRmax, respectively. Plasma volume decreased linearly in relation to intensity of weight lifting with mean responses of -7.7 +/- 0.8, -10.7 +/- 0.8, -12.1 +/- 0.9, and -13.9 +/- 0.8% at 40, 50, 60, and 70% of 1-RM, respectively. It was concluded that plasma volume decreases linearly in relation to intensity (%1-RM) of weight lifting and that the relation is similar to that reported for dynamic, low-resistance exercise such as cycling and running.