Changes in stroke volume and maximal aerobic capacity with increased blood volume in men and women

This study determined whether the effects of acute plasma volume expansion (PVX) or 10 days of training on stroke volume during submaximal cycling and on treadmill maximal oxygen uptake (Vo(2max)) were similar between men and women. Subjects performed a submaximal cycle test and a treadmill test to exhaustion under three conditions: control, PVX, and after training. Cycle peak Vo(2) (Vo(2peak)) and blood volume were measured before and after training. Training consisted of daily 1-h bouts [30 min at 80% peak heart rate (HR(peak)) and ten 2-min intervals at 95% HR(peak) alternating with 1-min low-intensity pedaling] on a cycle ergometer for 10 consecutive days. Training increased cycle Vo(2peak) in men [P < 0.05; 3.14 +/- 0.13 vs. 3.42 +/- 0.13 (SE) l/min] and women (2.11 +/- 0.10 vs. 2.37 +/- 0.12 l/min) and increased blood volume in men (67.6 +/- 3.0 vs. 72.3 +/- 3.1 ml/kg) and women (62.7 +/- 2.2 vs. 65.6 +/- 2.4 ml/kg). As a result of the greater blood volume with PVX and with training, stroke volume (mi) during submaximal cycling increased in men (control 110 +/- 4; PVX 123 +/- 4; trained 121 +/- 4) and women (control 87 +/- 5; PVX 95 +/- 6, trained 96 +/- 7). Treadmill Vo(2max) (ml . kg(-1). min(-1)) did not change with PVX despite a 6-7% reduction in hemoglobin concentration, whereas training resulted in an increase in Vo(2max) in men (control 47.9 +/- 2.8; PVX 46.7 +/- 2.8; trained 49.9 +/- 2.6) and women (control 38.0 +/- 1.2; PVX 36.9 +/- 1.2; trained 39.2 +/- 1.2), The effects of PVX or training on stroke volume or Vo(2max) did not differ between men and women. An additional finding was an increase in diastolic and mean blood pressures at 65% of cycle Vo(2peak) with PVX and with training in women. Thus men and women hold similar cardiac reserve capacities for increasing stroke volume and, as a result, Vo(2max) is maintained despite a reduction in hemoglobin concentration. However, gender differences in blood pressure regulation with increased blood volume might exist.