TY - JOUR

T1 - Resetting of the carotid arterial baroreflex during dynamic exercise in humans

AU - Norton, K H

AU - Boushel, Robert Christopher

AU - Andersen, Line Strange

AU - Saltin, B

AU - Raven, P B

PY - 1999/7/1

Y1 - 1999/7/1

N2 - Recent investigations have demonstrated that at the onset of low-to-moderate-intensity leg cycling exercise (L) the carotid baroreflex (CBR) was classically reset in direct relation to the intensity of exercise. On the basis of these data, we proposed that the CBR would also be classically reset at the onset of moderate- to maximal-intensity L exercise. Therefore, CBR stimulus-response relationships were compared in seven male volunteers by using the neck pressure-neck suction technique during dynamic exercise that ranged in intensity from 50 to 100% of maximal oxygen uptake (VO(2 max)). L exercise alone was performed at 50 and 75% VO(2 max), and L exercise combined with arm (A) exercise (L + A) was performed at 75 and 100% VO(2 max). O(2) consumption and heart rate (HR) increased in direct relation with the increases in exercise intensity. The threshold and saturation pressures of the carotid-cardiac reflex at 100% VO(2 max) were >75% VO(2 max), which were in turn >50% VO(2 max) (P <0.05), without a change in the maximal reflex gain (G(max)). In addition, the HR response value at threshold and saturation at 75% VO(2 max) was >50% VO(2 max) (P <0.05) and 100% VO(2 max) was >75% VO(2 max) (P <0.07). Similar changes were observed for the carotid-vasomotor reflex. In addition, as exercise intensity increased, the operating point (the prestimulus blood pressure) of the CBR was significantly relocated further from the centering point (G(max)) of the stimulus-response curve and was at threshold during 100% VO(2 max). These findings identify the continuous classic rightward and upward resetting of the CBR, without a change in G(max), during increases in dynamic exercise intensity to maximal effort.

AB - Recent investigations have demonstrated that at the onset of low-to-moderate-intensity leg cycling exercise (L) the carotid baroreflex (CBR) was classically reset in direct relation to the intensity of exercise. On the basis of these data, we proposed that the CBR would also be classically reset at the onset of moderate- to maximal-intensity L exercise. Therefore, CBR stimulus-response relationships were compared in seven male volunteers by using the neck pressure-neck suction technique during dynamic exercise that ranged in intensity from 50 to 100% of maximal oxygen uptake (VO(2 max)). L exercise alone was performed at 50 and 75% VO(2 max), and L exercise combined with arm (A) exercise (L + A) was performed at 75 and 100% VO(2 max). O(2) consumption and heart rate (HR) increased in direct relation with the increases in exercise intensity. The threshold and saturation pressures of the carotid-cardiac reflex at 100% VO(2 max) were >75% VO(2 max), which were in turn >50% VO(2 max) (P <0.05), without a change in the maximal reflex gain (G(max)). In addition, the HR response value at threshold and saturation at 75% VO(2 max) was >50% VO(2 max) (P <0.05) and 100% VO(2 max) was >75% VO(2 max) (P <0.07). Similar changes were observed for the carotid-vasomotor reflex. In addition, as exercise intensity increased, the operating point (the prestimulus blood pressure) of the CBR was significantly relocated further from the centering point (G(max)) of the stimulus-response curve and was at threshold during 100% VO(2 max). These findings identify the continuous classic rightward and upward resetting of the CBR, without a change in G(max), during increases in dynamic exercise intensity to maximal effort.

KW - Adult

KW - Baroreflex

KW - Blood Pressure

KW - Carotid Arteries

KW - Exercise

KW - Exercise Test

KW - Heart

KW - Heart Rate

KW - Humans

KW - Male

KW - Vasomotor System

M3 - Journal article

C2 - 10409592

VL - 87

SP - 332

EP - 338

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

SN - 8750-7587

IS - 1

ER -