Baroreflex responsiveness is attenuated in African Americans during steady‐state leg exercise

Abstract

Carotid baroreflex (CBR) responsiveness is impaired in African Americans (AA) compared to Caucasian Americans (CA) at rest. In addition, AA exhibit greater blood pressure responses to exercise compared to CA. We tested the hypothesis that CBR control of heart rate (HR) and mean arterial pressure (MAP) is reduced in AA compared to CA during steady‐state leg exercise. CBR control of HR and MAP was assessed in 11 AA and 11 CA subjects using 5s trials of neck pressure (NP, simulated hypotension: +45, +30, +15 Torr) and neck suction (NS, simulated hypertension: −20, −40, −60, −80 Torr). At rest, no racial differences were found in either the mean HR or the mean MAP responses to NP. While MAP responses to NS were similar between races at rest, the mean HR response to NS was attenuated in the AA group (−8.6±2.0bpm) compared to the CA group (−14.4±2.3bpm, p<0.05). During exercise (50% VO2peak), again no racial differences were found in either the mean HR or mean MAP responses to NP. However, the mean HR response to NS tended to be reduced in the AA group (−7.9±1.7bpm) compared to the CA group (− 11.0±3.1bpm, p=0.069) during exercise. Interestingly, the mean MAP response to NS was impaired in the AA group (− 6.5±0.8mmHg) compared to the CA group (−8.0±1.2mmHg, p<0.05) during exercise. These findings support inherent differences in CBR responsiveness in AA compared to CA during both rest and exercise.Support by NIH Grant R15HL096103