Resetting of the carotid arterial baroreflex during dynamic exercise in humans

Resetting of the carotid arterial baroreflex during dynamic exercise in hum ans. J. Appl. Physiol. 87(1): 332-338, 1999.-Recent investigations have dem onstrated that at the onset of low-to-moderate-intensity leg cycling exerci se (Lj the carotid baroreflex (CBR) was classically reset in direct relatio n to the intensity of exercise. On the basis of these data, we proposed tha t the CBR would also be classically reset at the onset of moderate- to maxi mal-intensity L exercise. Therefore, CBR stimulus-response relationships we re compared in seven male volunteers by using the neck pressure-neck suctio n technique during dynamic exercise that ranged in intensity from 50 to 100 % of maximal oxygen uptake (V overdot o(2max)) L exercise alone was perform ed at 50 and 75% V overdot o(2max) and L exercise combined with arm (A) exe rcise (L + A) was performed at 75 and 100% V overdot o(2max). O-2 consumpti on and heart rate (HR) increased in direct relation with the increases in e xercise intensity. The threshold and saturation pressures of the carotid-ca rdiac reflex at 100% V overdot o(2max) were >75% V overdot o(2max), which w ere in turn >50% V overdot o(2max), (P < 0.05), without a change in the max imal reflex gain (G(max)). In addition, the HR response value at threshold and saturation at 75% V overdot o(2) was >50% V overdot o(2max), (P < 0.05) and 100% V overdot o(2max) was >75% V overdot o(2max) (P < 0.07). Similar changes were observed for the carotid-vasomotor reflex. In addition, as exe rcise intensity increased, the operating point (the prestimulus blood press ure) of the CBR was significantly relocated further from the centering poin t (G(max)) of the stimulus-response curve and was at threshold during 100% V overdot o(2) These findings identify the continuous classic rightward and upward resetting of the CBR, without a change in G(max) during increases i n dynamic exercise intensity to maximal effort.