Exaggerated haemodynamic and neural responses to involuntary contractions induced by whole‐body vibration in normotensive obese versus lean women

Abstract

New Findings r What is the central question of this study?In obesity, the exaggerated blood pressure response to voluntary exercise is linked to hypertension, yet the mechanisms are not fully elucidated. We examined whether involuntary contractions elicit greater haemodynamic responses and altered neural control of blood pressure in normotensive obese versus lean women. r What is the main finding and its importance? During involuntary contractions induced by whole-body vibration, there were augmented blood pressure and spontaneous baroreflex responses in obese compared with lean women. This finding is suggestive of an overactive mechanoreflex in the exercise-induced hypertensive response in obesity. Passive contractions did not elicit differential heart rate responses in obese compared with lean women, implying other mechanisms for the blunted heart rate response reported during voluntary exercise in obesity.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 examined whether involuntary mechanical oscillations, induced by whole-body vibration (WBV), elicit greater haemodynamic responses and altered neural control of BP in obese versus lean women. Twenty-two normotensive, premenopausal women (12 lean and 10 obese) randomly underwent a passive WBV (25 Hz) and a control protocol (similar posture without WVB). Beat-by-beat BP, heart rate, stroke volume, systemic vascular resistance, cardiac output, parasympathetic output (evaluated by heart rate variability) and spontaneous baroreceptor sensitivity (sBRS) were assessed. We found that during WBV, obese women exhibited an augmented systolic BP response compared with lean women 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 versus lean women, associated with a greater stroke volume index in obese women. Involuntary contractions did not elicit a differential magnitude of responses in heart rate, heart rate variability indices and systemic vascular resistance in obese versus lean women; however, they did result in greater sBRS responses (P < 0.05) in obese women. In conclusion, involuntary contractions elicited an augmented BP and sBRS response in normotensive obese versus lean women. The

Whole-body vibration training in obese subjects: A systematic review

“…NOx decreases systolic BP and AIx reducing the vascular tone of small arteries [84]. Second, the mechanical oscillatory contractions during vibration serve as an active muscle pump and increase stroke volume, probably enhancing venous return and preload [85]. Third, total peripheral resistance to blood flow increases during body vibration.…”

“…WBVT could be prescribed without additional exercise in the initial stages of a weight loss program, due to the limited stress upon joints and the GH-mediated stimulation of metabolism, without provoking an excessive fatigue [63,85]. Passive vibrations do not involve voluntary movement and require a lower contribution of central command [98].…”

Effects of whole‐body vibration on heart rate variability: acute responses and training adaptations

“…Dipla et al . () assigned normotensive lean and obese women to 6 min of PV (frequency 25 Hz, amplitude 6 mm) with the knee flexed at 18° angle. Greater HR increases were noted during PV than control standing without PV in both lean and obese women (no between‐group differences).…”

Augmented Hemodynamic Responses in Obese Young Men during Dynamic Exercise: Role of the Muscle Metaboreflex

“…Regular exercise has been shown to reduce body fat as well as protect against cardiovascular diseases associated with obesity [ 6 , 7 , 8 ]. On the other hand, obesity produces excessive increases in arterial blood pressure (BP) during exercise [ 9 , 10 ]. These augmented BP responses may increase the risk of cardiac events associated with exercise (e.g., stroke, acute myocardial infarction) [ 11 , 12 , 13 ].…”

“…This study demonstrated that hemodynamic responses mediated by the MMR are not augmented and the muscle vasodilatory responses are not altered in obese women. In contrast, another study investigated that a whole-body vibration caused exaggerated BP responses in normotensive obese women and suggested that this excessive response may be attributed to a mechanoreflex disfunction [ 9 ]. The inconsistency in BP response induced by the MMR activation could be due to differences in muscle mass (i.e., handgrip exercise vs. whole body exercise).…”