Exercise training mode affects the hemodynamic responses to lower body negative pressure in women

To determine if different exercise modes used to improve cardiovascular fitness result in differing cardiovascular responses to lower body negative pressure (LBNP) in exercise-trained women, seven chronically exercising female runners (RUN) and 11 swimmers (SWIM) of similar fitness levels maximal oxygen uptake, [VO(2max), mean (SEM) = 50 (2) and 45 (2) ml*kg(-1)*min(-1), respectively; P > 0.05] underwent serial exposures to LBNP at pressures of 0, -1.3, -2.7 and -5.3 kPa (referenced to ambient barometric pressure). Forearm vascular resistance (venous occlusion plethysmography) increased with LBNP but did not differ between groups at any level of LBNP. At 0 and - 1.3 kPa, the total peripheral resistance index (TPRI; impedance cardiography) was significantly (P <0.05) higher in RUN than SWIM [1.118(0.028) vs 0.787 (0.040) at 0 kPa and 1.245 (0.100) vs 0.840 (0.040) 2 kPa*l* min(-1)*m(-2) at -1.3kPa]. At an LBNP of -2.7kPa, stroke index (SI) was significantly higher in SWIM than RUN [57.8(4.6) vs 41.9 (4.0) ml*beat(-1)*m(-2)] while TPRI remained greater in RUN than SWIM. At -5.3 kPa, SWIM exhibited a higher cardiac index [3.232 (0.209) vs 2.447 (0.189) l*min(-1)*m(-2)] and SI [49.4 (4.4) vs 31.0 (4.5) ml *beat(-1)*m(-2)] but reduced heart rate [71(3) vs 83(5) beats . min(-1)] and TPRI [0.968 (0.043) vs 1.655 (0.128) kPa*1*min(-1)* m(-2)]. Mean arterial pressure declined significantly at an LBNP of -5.3 kPa in both groups; pulse pressure was lower (P <0.05) in RUN than SWIM at LBNP values of -2.7 and -5.3 kPa. These data suggest that: (1) female runners experience a greater increase in systemic vasoconstriction even though female swimmers can better maintain their cardiac index at high levels of LBNP, and (2) training mode appears to affect the pulse pressure responses to LBNP in exercise-trained women.