Exaggerated hemodynamic and neural responses to involuntary contractions induced by whole body vibration in normotensive obese vs. lean women

In obesity, the exaggerated blood pressure (BP) response to exercise is linked to hypertension, yet the mechanisms are not fully elucidated. In this study, we aimed at examining whether involuntary mechanical oscillations, induced by whole-body-vibration (WBV), elicit greater hemodynamic responses and altered neural control of BP, in obese vs. lean women. Twenty-two normotensive, pre-menopausal women (lean = 12, obese = 10) performed randomly a passive WBV (25 Hz) and a control (similar posture without WVB) protocol. Beat-by-beat BP, heart rate (HR), stroke volume, systemic vascular resistance (SVR), cardiac output, parasympathetic output [evaluated by heart rate variability (HRV)] and spontaneous baroreceptor sensitivity (sBRS) were assessed. Results: During WBV, obese exhibited an augmented systolic BP response vs. lean that was correlated with body fat percentage (R = 0.77; p<0.05). The exaggerated BP rise was driven mainly by the greater increase in cardiac output index in obese vs. lean, associated with a greater stroke volume index in obese. Involuntary contractions did not elicit a differential magnitude of responses in HR, HRV indices, and SVR in obese vs. lean; however, they did result in greater sBRS responses (p<0.05) in obese. Conclusions: Involuntary contractions elicited an augmented BP and sBRS response in normotensive obese vs. lean. The greater elevations in circulatory hemodynamics in obese, are suggestive of an overactive mechanoreflex in the exercise-induced hypertensive response in obesity.

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