Fourteen young male volunteers (mean age 28.1 yr) underwent maximal exercise performance testing and lower body negative pressure (LBNP) challenge to -50 Torr. Two distinct groups, fit (F, n = 8), mean maximal aerobic capacity (V̇O(2 max)) = 70.2 ± 2.6 (SE) ml O2 kg-1.min-1, and average fit (AF, n = 6), mean V̇O(2 max)) = 41.3 ± 2.9 ml O2 kg-1.min-1, P<0.001, were evaluated. Rebreathing CO2 cardiac outputs, heart rate (HR), blood pressure (BP), and leg circumference changes were monitored at each stage of progressive increases in LBNP to -50 Torr. The overall hemodynamic responses of both groups of subjects to LBNP were qualitatively similar to previous findings. There were no differences between F and AF in peripheral venous pooling as shown by a leg compliance (Δ leg volume/Δ LBNP) for the F of 12.6 ± 1.1 and for the AF 11.6 ± 2.0 P<0.05. The F subjects had significantly less tachycardic response [ΔHR/Δ systolic BP of F = 0.7 beats/Torr] to LBNP to -50 Torr than the AF subjects [ΔHR/Δ systolic BP of unfit (UF) = 1.36 beats/Torr], P<0.05. In addition, overall calculated peripheral vascular resistance was significantly higher in the AF subjects (P<0.001), and there was a more marked decrease in systolic BP of the F subjects between the LBN pressures of -32 to -50 Torr. We concluded that the reflex response to central hypovolemia was altered by endurance exercise training.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Applied Physiology Respiratory Environmental and Exercise Physiology|
|State||Published - 1984|
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