| Keywords |
Prehypertension women ; Exercise pressor reflex ; Muscle group III afferent ; Passive tendon stretch |
| Abstract |
It was suggested that the exercise pressor reflex (EPR) plays an important role to regulate the cardiovascular responses during dynamic exercise. A component of EPR, group III mechanoreceptors evoked excessive blood pressure response in hypertensive rats during passive tendon stretch. But it is not known that this exaggerated blood pressure response to passive tendon stretch is mediated by EPR overactivity in prehypertensive women. Therefore, this study was to investigate the physiological responses in both normotension and prehypertension during passive tendon stretch. Twenty subjects (10 prehypertension and 10 normotension) with a mean age 49.0±3.4 years were recruited for this study. All subjects were continuously instrumented to measure stroke volume (SV), heart rate (HR), cardiac output (CO), total vascular conductance (TVC) throughout the experiment. To stimulate the group III mechanoreceptors, brief passive dorsiflexion of the foot was performed by a cybex for one minute. The results showed that mean arterial blood pressure was significantly increased during dorsiflexion in both groups, however, this pressor response was significantly higher in prehypertensive women. SV and CO were significantly increased in normotensive women, while there were no differences in prehyperentsive women. There was no difference in HR in both groups. TVC was significantly decreased in prehypertension, while no difference in normotension. It is concluded that the excessive pressor response mediated by dorsiflexion is occurred by overactivity of group III mechanorecptors and the mechanism is produced via mainly peripheral vasoconstriction in prehypertensive women. |