Cardiovascular Responses to Maximal Graded and Acute Lower Body Negative Pressure

This investigation attempted to determine whether heart-rate and blood pressure responses to maximal acute lower body negative pressure (LBNP) are exacerbated compared with maximal graded LBNP in active older ( n  = 9, 70 ± 7 yr) and endurance-trained younger ( n  = 10, 23 ± 3 yr) individuals. Heart rate increased earlier during graded LBNP in the younger group (−40 mm Hg vs. tolerance) and was significantly higher than that of the older adults at the point of tolerance. Mean arterial pressure (MAP) decreased more in the older than the younger individuals during graded LBNP. LBNP-tolerance index was significantly greater in the younger group (309 ± 52 vs. 255.6 ± 48 mm Hg/min). Acute doses of LBNP elicited slower heart-rate responses in the older group. Despite these age-related differences, MAP responses were not different between groups with acute LBNP, so age per se does not appear to predispose individuals to orthostatic intolerance.