TY - JOUR
T1 - Reduction in lbnp tolerance following prolonged endurance exercise training
AU - Stevens, Glen H.J.
AU - Foresman, Brian H.
AU - Shi, Xiangrong
AU - Stern, Stephen A.
AU - Raven, Peter B.
PY - 1992/11
Y1 - 1992/11
N2 - Eight young men underwent an 8-month endurance exercise training program. Prior to and following the training program, the subjects’ maximal oxygen uptake (VO2max), total blood volume (TBV) and plasma volume (PV), tolerance to lower body negative pressure (LBNP) assessed by the cumulative stress index (CSI) to presyncope, and their hemodynamic responses to 0 to -45 torr LBNP was determined. Hemodynamic measures included rebreathe carbon dioxide cardiac output (Qc). heart rate (HR), directly measured arterial blood pressures (ABP), and strain gauge determination of forearm blood flow (FBF) and leg volume changes (ALgV). Calculated values of stroke volume (SV), forearm, vascular resistance (FVR), and peripheral vascular resistance (PVR) were made. Following training, each subject had an increased VO2max(x = +27.4%, P< 0.001), TBV (x = +15.8%, P< 0.02), and PV (x = +16.5%, P < 0.02) and each subject had a decreased tolerance to LBNP (x CSI = −24%, P < 0.001). Stepwise linear regression identified that the major factors to significantly predict the decreased CSI pre- to post-training were a reduced response of PVR to LBNP from −15 to −45 torr (Model R2 = 0.853), the A TBV (model R2 = 0.981), and the greater post-training reduction in SBP to LBNP of 0 to -45 torr (model R2 = 1.0). These data suggest that physiologic adaptations associated with the increased VO2max and TBV resulting from a prolonged endurance exercise training program can alter the reflex control of vasomotion and cardiac output during LBNP and reduce the LBNP tolerance.
AB - Eight young men underwent an 8-month endurance exercise training program. Prior to and following the training program, the subjects’ maximal oxygen uptake (VO2max), total blood volume (TBV) and plasma volume (PV), tolerance to lower body negative pressure (LBNP) assessed by the cumulative stress index (CSI) to presyncope, and their hemodynamic responses to 0 to -45 torr LBNP was determined. Hemodynamic measures included rebreathe carbon dioxide cardiac output (Qc). heart rate (HR), directly measured arterial blood pressures (ABP), and strain gauge determination of forearm blood flow (FBF) and leg volume changes (ALgV). Calculated values of stroke volume (SV), forearm, vascular resistance (FVR), and peripheral vascular resistance (PVR) were made. Following training, each subject had an increased VO2max(x = +27.4%, P< 0.001), TBV (x = +15.8%, P< 0.02), and PV (x = +16.5%, P < 0.02) and each subject had a decreased tolerance to LBNP (x CSI = −24%, P < 0.001). Stepwise linear regression identified that the major factors to significantly predict the decreased CSI pre- to post-training were a reduced response of PVR to LBNP from −15 to −45 torr (Model R2 = 0.853), the A TBV (model R2 = 0.981), and the greater post-training reduction in SBP to LBNP of 0 to -45 torr (model R2 = 1.0). These data suggest that physiologic adaptations associated with the increased VO2max and TBV resulting from a prolonged endurance exercise training program can alter the reflex control of vasomotion and cardiac output during LBNP and reduce the LBNP tolerance.
KW - Arterial baroreflexes
KW - Blood pressure regulation
KW - Central hypovolemia
KW - Maximal aerobic capacity
KW - Orthostatic tolerance
KW - Peripheral vascular resistance
KW - Total blood volume
UR - http://www.scopus.com/inward/record.url?scp=0026475421&partnerID=8YFLogxK
U2 - 10.1249/00005768-199211000-00007
DO - 10.1249/00005768-199211000-00007
M3 - Article
C2 - 1435175
AN - SCOPUS:0026475421
VL - 24
SP - 1235
EP - 1244
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
SN - 0195-9131
IS - 11
ER -