Effects of exercise training mode on the cardiovascular responses to lower body negative pressure in males

Abstract

Background: Endurance-trained males may be more prone to orthostatic hypotension than untrained subjects and this is reflected in differences in their cardiovascular responses to lower body negative pressure (LBNP). It is uncertain if the type of endurance training used affects these responses.

Hypothesis: Endurance-trained runners will differ from endurance-trained swimmers in their cardiovascular responses to LBNP.

Methods: Male intercollegiate cross country runners (XC, n = 9), sprinters (SP, n = 7) and swimmers (SW, n = 12) underwent exposures to -10, -20 and -40 mm Hg LBNP. Forearm blood flow, heart rate (HR) and blood pressure were measured throughout. Maximal oxygen consumption (VO2max) was determined separately via combined arm-and-leg cycle ergometry.

Results: The XC were more fit than the SW and SP (VO2max = 64.5 +/- 3.5 vs. 51.7 +/- 1.9, 49.5 +/- 2.4 ml.kg-1.min-1; x +/- SEM; p < 0.05). Resting mean arterial pressure (MAP, 93 +/- 3 mm Hg) and forearm vascular resistance (FVR; 26.2 +/- 6.0 units) did not differ significantly between groups although HR was 17 +/- 3 b.min-1 higher (p < 0.05) in SW vs. SP and XC. Neither the pulse pressure, MAP, HR, nor FVR responses to the LBNP exposures differed significantly between the 3 groups. Compared to rest, pulse pressure was reduced (p < 0.05) 14% at -40 mm Hg. Similarly, HR was increased (p < 0.05) 10% at -40 mm Hg. FVR increased (p < 0.05) with each increase in LBNP becoming 91% greater at -40 mm Hg vs. rest.

Conclusions: These data suggest that the cardiovascular responses to LBNP up to -40 mm Hg do not differ in chronically exercising males training with different modalities.