Altered hemodynamic regulation and reflex control during exercise and recovery in obese boys

Abstract

The aims of the present study were to assess in obese and lean boys 1) the hemodynamic responses and baroreflex sensitivity (BRS) to isometric handgrip exercise (HG) and recovery and 2) the muscle metaboreflex-induced blood pressure response and the variables that determine this response. Twenty-seven boys (14 obese and 13 lean boys, body mass index: 29.2 ± 0.9 vs. 18.9 ± 0.3 kg/m(2), respectively) participated. The testing protocol involved 3 min of baseline, 3 min of HG (30% maximum voluntary contraction), 3 min of circulatory occlusion, and 3 min of recovery. The same protocol was repeated without occlusion. At baseline, no differences were detected between groups in beat-to-beat arterial pressure (AP), heart rate (HR), and BRS; however, obese boys had higher stroke volume and lower total peripheral resistance than lean boys (P < 0.05). During HG, lean boys exhibited higher HR and lower BRS compared with their obese counterparts. In lean boys, BRS decreased during HG compared with baseline, whereas in obese boys, it was not significantly modified. In lean boys, TPR was elevated during HG and declined after exercise, whereas in obese boys, TPR did not significantly decrease after exercise cessation. In the postexercise period, BRS in lean boys returned to baseline, whereas an overshoot was observed in obese boys. Postexercise BRS was correlated with body mass index (R = 0.56, P < 0.05). Although the metaboreflex-induced increase in AP was similar between obese and lean children, it was achieved via different mechanisms: in lean children, total peripheral resistance was the main contributor to AP maintenance during the metaboreflex, whereas in obese children, stroke volume significantly contributed to AP maintenance during the metaboreflex. In conclusion, obese normotensive children demonstrated altered cardiovascular hemodynamics and reflex control during exercise and recovery.

Differences in hemodynamic response to metaboreflex activation between obese patients with metabolic syndrome and healthy subjects with obese phenotype

“…We cannot provide an explanation for the phenomenon, but it is not the first time that it has been reported, since Fournier et al (17) described similar behavior in subjects with metabolic syndrome.…”

“…We cannot provide a definitive explanation for this fact. However, some studies have reported that obesity with metabolic syndrome can be associated with diastolic dysfunction and abnormalities in left ventricular relaxation (17,28,48), although the described abnormal diastolic function is not unanimously reported (52). Thus it is possible to hypothesize that impairment in ventricular diastolic function hampered the normal diastolic filling in subjects with OMS, and this fact in turn resulted in the impaired VFR response.…”

“…It has been reported that patients with metabolic syndrome can show signs of impaired left ventricular function during exercise (17). Furthermore, there is evidence that obesity can alter left ventricular systolic function, which has been attributed to calcium modulation during the cardiac cycle (44).…”

“…Moreover, notwithstanding sympathetic overdrive at rest is considered a hallmark of obesity, research regarding sympathetic tone in obese patients during the metaboreflex has yielded conflicting results (17,36,57). In particular, although sympathetic activity at rest has been usually found increased, the muscle metaboreflex control on sympathetic tone has been reported to be blunted in these patients (36,57).…”

Frequency domain analysis of heart rate variability in young obese adults with parental history of hypertension during isotonic exercise: A comparative study

“…In spite of limitation of less sample size and wide distribution of values, the present study emphasizes the necessity to improve vagal tone and lower sympathetic tone in obese young adults with hypertensive parents, so that they do not progress into the stage of prehypertension. [26] …”