Gianmarco Sainas

Ischemic preconditioning reduces hemodynamic response during metaboreflex activation

Ischemic preconditioning (IP) has been shown to improve exercise performance and to delay fatigue. However, the precise mechanisms through which IP operates remain elusive. It has been hypothesized that IP lowers the sensation of fatigue by reducing the discharge of group III and IV nerve endings, which also regulate hemodynamics during the metaboreflex. We hypothesized that IP reduces the blood pressure response during the metaboreflex. Fourteen healthy males (age between 25 and 48 yr) participated in this study. They underwent the following randomly assigned protocol: postexercise muscle ischemia (PEMI) test, during which the metaboreflex was elicited after dynamic handgrip; control exercise recovery session (CER) test; and PEMI after IP (IP-PEMI) test. IP was obtained by occluding forearm circulation for three cycles of 5 min spaced by 5 min of reperfusion. Hemodynamics were evaluated by echocardiography and impedance cardiography. The main results were that after IP the mean arterial pressure response was reduced compared with the PEMI test (means ± SD +3.37 ± 6.41 vs. +9.16 ± 7.09 mmHg, respectively). This was the consequence of an impaired venous return that impaired the stroke volume during the IP-PEMI more than during the PEMI test (-1.43 ± 15.35 vs. +10.28 ± 10.479 ml, respectively). It was concluded that during the metaboreflex, IP affects hemodynamics mainly because it impairs the capacity to augment venous return and to recruit the cardiac preload reserve. It was hypothesized that this is the consequence of an increased nitric oxide production, which reduces the possibility to constrict venous capacity vessels.

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

Patients suffering from obesity and metabolic syndrome (OMS) manifest a dysregulation in hemodynamic response during exercise, with an exaggerated systemic vascular increase. However, it is not clear whether this is the consequence of metabolic syndrome per se or whether it is due to concomitant obesity. The aim of the present investigation was to discover whether OMS and noncomplicated obesity resulted in different hemodynamic responses during the metaboreflex. Twelve metabolically healthy but obese subjects (MHO; 7 women), 13 OMS patients (5 women), and 12 normal age-matched controls (CTL; 6 women) took part in this study. All participants underwent a postexercise muscle ischemia protocol to evaluate the metaboreflex activity. Central hemodynamics were evaluated by impedance cardiography. The main result shows an exaggerated increase in systemic vascular resistance from baseline during the metaboreflex in the OMS patients as compared with the other groups (481.6 ± 180.3, -0.52 ± 177.6, and -60.5 ± 58.6 dynes·s(-1)·cm(-5) for the OMS, the MHO, and the CTL groups, respectively; P < 0.05). Moreover, the MHO subjects and the CTL group showed an increase in cardiac output during the metaboreflex (288.7 ± 325.8 and 703.8 ± 276.2 ml/m increase with respect to baseline), whereas this parameter tended to decrease in the OMS group (-350 ± 236.5 ml/m). However, the blood pressure response, which tended to be higher in the OMS patients, was not statistically different between groups. The results of the present investigation suggest that OMS patients have an exaggerated vasoconstriction in response to metaboreflex activation and that this fact is not due to obesity per se.

Hemodynamic response to muscle reflex is abnormal in patients with heart failure with preserved ejection fraction

The aim of the present investigation was to assess the role of cardiac diastole on the hemodynamic response to metaboreflex activation. We wanted to determine whether patients with diastolic function impairment showed a different hemodynamic response compared with normal subjects during this reflex. Hemodynamics during activation of the metaboreflex obtained by postexercise muscle ischemia (PEMI) was assessed in 10 patients with diagnosed heart failure with preserved ejection fraction (HFpEF) and in 12 age-matched healthy controls (CTL). Subjects also performed a control exercise-recovery test to compare data from the PEMI test. The main results were that patients with HFpEF achieved a similar mean arterial blood pressure (MAP) response as the CTL group during the PEMI test. However, the mechanism by which this response was achieved was markedly different between the two groups. Patients with HFpEF achieved the target MAP via an increase in systemic vascular resistance (+389.5 ± 402.9 vs. +80 ± 201.9 dynes·s-1·cm-5 for HFpEF and CTL groups respectively), whereas MAP response in the CTL group was the result of an increase in cardiac preload (-1.3 ± 5.2 vs. 6.1 ± 10 ml in end-diastolic volume for HFpEF and CTL groups, respectively), which led to a rise in stroke volume and cardiac output. Moreover, early filling peak velocities showed a higher response in the CTL group than in the HFpEF group. This study demonstrates that diastolic function is important for normal hemodynamic adjustment to the metaboreflex. Moreover, it provides evidence that HFpEF causes hemodynamic impairment similar to that observed in systolic heart failure.NEW & NOTEWORTHY This study provides evidence that diastolic function is important for normal hemodynamic responses during the activation of the muscle metaboreflex in humans. Moreover, it demonstrates that diastolic impairment leads to hemodynamic consequences similar to those provoked by systolic heart failure. In both cases the target blood pressure is obtained mainly by means of exaggerated vasoconstriction than by a flow-mediated mechanism.

Occurrence of cardiac output decrease (via stroke volume) is more pronounced in women than in men during prolonged dry static apnea

Little is known about sex differences in autonomic cardiovascular regulation of the diving response, and the few available studies of these differences were conducted on subjects with limited or no diving experience. We examined the influence of sex on hemodynamics during dry static apnea (SA) in eight male and eight female elite divers matched for their breath hold (BH) ability. Hemodynamics was assessed by means of simultaneous echocardiography and impedance cardiography measurements, and arterial pressure and oxygen saturation ([Formula: see text]) were also collected. In the first quarter (AP25%) and half (AP50%) of apnea duration cardiac output (CO) showed a more rapid and intense decrease in women than in men (-43% vs. -17% during AP25% and -40% vs. -19% during AP50%, respectively, P < 0.05). At the same time points, systemic vascular resistance (SVR) increased more in women than in men (+22% vs. +100% at AP25% and +48% vs. +107% at AP50%, respectively, P < 0.05). [Formula: see text] progressively declined in both groups, but men showed a more pronounced decrease than women at the end of apneas (-13% vs. -5%, respectively, P < 0.05). In men the higher the body surface area values the longer the apnea, while in women the higher the SVR response the longer the apnea. In elite female divers, the magnitude of CO decrease during dry SA was larger than in male divers. The capacities to store oxygen and to reduce O2 consumption play a pivotal role in BH performance, but their extent seems to be different in the sexes. NEW & NOTEWORTHY This is the first study in which the influence of sex on hemodynamics during dry static apnea has been investigated in two groups of elite divers matched for their breath hold ability. We also show the correlation between the performances obtained by divers during a real competition and their anthropometric, respiratory, and cardiovascular characteristics.

Metaboreflex-mediated hemodynamic abnormalities in individuals with coronary artery disease without overt signs or symptoms of heart failure

This study was devised to investigate the effect of coronary artery disease (CAD) without overt signs of heart failure on the cardiovascular responses to muscle metaboreflex activation. We hypothesized that any CAD-induced preclinical systolic and/or diastolic dysfunction could impair hemodynamic response to the metaboreflex test. Twelve men diagnosed with CAD without any sign or symptoms of heart failure and 11 age-matched healthy control (CTL) subjects participated in the study. Subjects performed a postexercise muscle ischemia (PEMI) test to activate the metaboreflex. They also performed a control exercise recovery test to compare data from the PEMI test. The main results were that the CAD group reached a similar mean arterial blood pressure response as the CTL group during PEMI. However, the mechanism by which this response was achieved was different between groups. In particular, CAD achieved the target mean arterial blood pressure by increasing systemic vascular resistance (+383.8 ± 256.6 vs. +91.2 ± 293.5 dyn·s-1·cm-5 for the CAD and CTL groups, respectively), the CTL group by increasing cardiac preload (-0.92 ± 8.53 vs. 5.34 ± 4.29 ml in end-diastolic volume for the CAD and CTL groups, respectively), which led to an enhanced stroke volume and cardiac output. Furthermore, the ventricular filling rate response was higher in the CTL group than in the CAD group during PEMI ( P < 0.05 for all comparisons). This study confirms that diastolic function is pivotal for normal hemodynamics during the metaboreflex. Moreover, it provides evidence that early signs of diastolic impairment attributable to CAD can be detected by the metaboreflex test. NEW & NOTEWORTHY Individuals suffering from coronary artery disease without overt signs of heart failure may show early signs of diastolic dysfunction, which can be detected by the metaboreflex test. During the metaboreflex, these subjects show impaired preload and stroke volume responses and exaggerated vasoconstriction compared with controls.

Case Study: Physical Capacity and Nutritional Status Before and After a Single-Handed Yacht Race

During solitary sailing, the sailor is exposed to sleep deprivation and difficulties in consuming regular meals. Sailor weight loss is often reported. In the present case study, we describe changes in the physical capacity and nutritional status of an athlete attempting a single-handed yacht race around the globe. An Italian male ocean racer (Gaetano Mura) asked for our help to reach an optimum level of physical and nutritional preparation. We planned his diet after assessing his anthropometric parameters and body composition, as well as his usual energy intake and nutritional expenditure. The diet consisted of 120 meals stored in sealed plastic bags. Before his departure, GM performed two incremental exercise tests (cycle ergometry and arm crank ergometry) to assess his physical capacity. Cardiac functions were also estimated by Doppler echocardiography. All measures and exercise tests were repeated 10 days after GM finished the race, which lasted 64 days. Anthropometric measures did not change significantly, with the exception of arm fat area and thigh muscle area, which decreased. There were evident increments in maximum oxygen intake and maximum workload during arm cranking after the race. On the contrary, maximum oxygen uptake and maximum workload decreased during cycling. Finally, end-diastolic and stroke volume decreased after the race. It was concluded that nutritional counseling was useful to avoid excessive changes in nutritional status and body composition due to 64 days of solitary navigation. However, a reduction in physical leg capacity and cardiovascular functions secondary to leg disuse were present.