Norepinephrine spillover from skeletal muscle during exercise in humans: role of muscle mass

TY - JOUR

T1 - Norepinephrine spillover from skeletal muscle during exercise in humans

T2 - role of muscle mass

AU - Savard, G K

AU - Richter, Erik

AU - Strange, S

AU - Kiens, Bente

AU - Christensen, Niels Juel

AU - Saltin, Bengt

PY - 1989

Y1 - 1989

N2 - The purpose of this study was to determine the effect of increasing muscle mass involvement in dynamic exercise on both sympathetic nervous activation and local hemodynamic variables of individual active and inactive skeletal muscle groups. Six male subjects performed 15-min bouts of one-legged knee extension either alone or in combination with the knee extensors of the other leg and/or with the arms. The range of work intensities varied between 24 and 71% (mean) of subjects' maximal aerobic capacity (% VO2max). Leg blood flow, measured in the femoral vein by thermodilution, was determined in both legs. Arterial and venous plasma concentrations of norepinephrine (NE) and epinephrine were analyzed, and the calculated NE spillover was used as an index of sympathetic nervous activity to the limb. NE spillover increased gradually both in the resting, and to a larger extent in the exercising legs, with a steeper rise occurring approximately 70% VO2max. These increases were not associated with any significant changes in leg blood flow or leg vascular conductance at the exercise intensities examined. These results suggest that, as the total active muscle mass increases, the rise in sympathetic nervous activity to skeletal muscle, either resting or working at a constant load, is not associated with any significant neurogenic vasoconstriction and reduction in flow or conductance through the muscle vascular bed, during whole body exercise demanding up to 71% VO2max.

AB - The purpose of this study was to determine the effect of increasing muscle mass involvement in dynamic exercise on both sympathetic nervous activation and local hemodynamic variables of individual active and inactive skeletal muscle groups. Six male subjects performed 15-min bouts of one-legged knee extension either alone or in combination with the knee extensors of the other leg and/or with the arms. The range of work intensities varied between 24 and 71% (mean) of subjects' maximal aerobic capacity (% VO2max). Leg blood flow, measured in the femoral vein by thermodilution, was determined in both legs. Arterial and venous plasma concentrations of norepinephrine (NE) and epinephrine were analyzed, and the calculated NE spillover was used as an index of sympathetic nervous activity to the limb. NE spillover increased gradually both in the resting, and to a larger extent in the exercising legs, with a steeper rise occurring approximately 70% VO2max. These increases were not associated with any significant changes in leg blood flow or leg vascular conductance at the exercise intensities examined. These results suggest that, as the total active muscle mass increases, the rise in sympathetic nervous activity to skeletal muscle, either resting or working at a constant load, is not associated with any significant neurogenic vasoconstriction and reduction in flow or conductance through the muscle vascular bed, during whole body exercise demanding up to 71% VO2max.

KW - Adult

KW - Arm

KW - Blood Pressure

KW - Cardiac Output

KW - Epinephrine

KW - Heart Rate

KW - Humans

KW - Leg

KW - Male

KW - Muscles

KW - Norepinephrine

KW - Oxygen

KW - Oxygen Consumption

KW - Physical Exertion

KW - Reference Values

KW - Regional Blood Flow

M3 - Journal article

C2 - 2603969

SN - 0002-9513

VL - 257

SP - H1812-H1818

JO - American Journal of Physiology

JF - American Journal of Physiology

IS - 6 Pt 2

ER -