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 expan sion (PVX) or 10 days of training on stroke volume during submaximal c ycling 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, a nd after training. Cycle peak Vo(2) (Vo(2peak)) and blood volume were measured before and after training. Training consisted of daily 1-h bo uts [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 cy cle ergometer for 10 consecutive days. Training increased cycle Vo(2pe ak) 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 volu me 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 wit h 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). Treadmi ll Vo(2max) (ml . kg(-1). min(-1)) did not change with PVX despite a 6 -7% reduction in hemoglobin concentration, whereas training resulted i n 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 additiona l 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 vo lume and, as a result, Vo(2max) is maintained despite a reduction in h emoglobin concentration. However, gender differences in blood pressure regulation with increased blood volume might exist.