Cerebral blood flow during sprint exercise

Se desconocen los efectos del entrenamiento interválico de alta intesidad (HIIT) sobre el flujo sanguíneo cerebral (FSC) y la oxigenación cerebral. Por ello reclutamos a 20 voluntarios que realizaron una sesión de HIIT (4 test de Wingate con recuperaciones de 4 minutos). Se midió la oxigenación del lóbulo frontal (OLF) y el Vastus lateralis (VL) a través de espectrofotometría cercana a los infrarrojos (NIRS). También se registró la velocidad de la sangre en las arterias cerebrales medias (vACM) mediante Doppler. La vACM disminuyó entre un 5 y 10 % en el primer esprint. En los siguientes esprints se redujo aún más. La vACM descendió en cada esprint coincidiendo con la disminución de la presión tele-espiratoria de dióxido de carbono (PETCO2) y con valores superiores de ventilación pulmonar (VE). Al interrumpirse el pedaleo se redujo bruscamente la vACM. Sin embargo, la OLF se mantuvo estable en el primer esprint sólo reduciéndose ligeramente durante el segundo y tercer Wingate (el cuarto fue similar al tercero). Este estudio muestra que la vACM disminuye durante los ejercicios de esprint, posiblemente debido a la hipocapnia. La reducción de la vACM no ejerce efectos funcionales ni relevantes sobre la oxigenación cerebral, gracias al ajuste de la conductancia vascular a través de los mecanismos de autoregulación, sin que parezca afectar negativamente al rendimiento.The effect of high-intensity interval training (HIIT) on cerebral blood flow (CBF) and cerebral oxygenation remain unknown. Therefore, we recruited 20 voluntaries who performed one HIIT session (4x30s Wingate tests with 4 minutes recovery between them). We measured frontal lobe (FLO) and Vastus lateralis (VL) oxygenation with NIRS. Middle cerebral artery blood flow velocity (MCAv) was measured by Doppler. MCAv decreased between 5 and 10 % during the first sprint. MCAv decreased slightly more during the subsequent sprints. Nevertheless, FLO remained stable during the first sprint and was only reduced slightly during the second and third Wingate (the fourth was similar to the third). MCAv decreased on each sprint with the reduction of End-tidal carbon dioxide pressure (PETCO2), the latter due to hyperventilation. When subjects stopped pedaling MCAv was dropped markedly. The decrease in MCAv did not produce any functional or relevant effect on frontal lobe oxygenation due to the adjustment of cerebral vascular conductance by the auto-regulatory mechanisms and did not seem to negatively affect performance.Sin financiaciónNo data JCR 2016No data SJR 20160.420 IDR (2016) C2, 17/42 Deport

Treatment of hypertension with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and resting metabolic rate: A cross-sectional study

Hypertension in obese and overweight patients is associated with an elevated resting metabolic rate (RMR). The aim of this study was to determine whether RMR is reduced in hypertensive patients treated with angiotensin-converting enzyme inhibitors (ACEI) and blockers (ARB). The RMR was determined by indirect calorimetry in 174 volunteers; 93 (46.5 %) were hypertensive, of which 16 men and 13 women were treated with ACEI/ARB, while 30 men and 19 women with untreated hypertension served as a control group. Treated and untreated hypertensives had similar age, BMI, physical activity, and cardiorespiratory fitness. The RMR normalized to the lean body mass (LBM) was 15% higher in the untreated than ACEI/ARB-treated hypertensive women (p = .003). After accounting for LBM, whole-body fat mass, age, the double product (heart rate x systolic blood pressure), and the distance walked per day, the RMR was 2.9% lower in the patients taking ACEI/ARB (p = .26, treatment x sex interaction p = .005). LBM, age, and the double product explained 78% of the variability in RMR (R2 = 0.78, p < .001). In contrast, fat mass, the distance walked per day, and total T4 or TSH did not add predictive power to the model. Compared to men, a greater RMR per kg of LBM was observed in untreated hypertensive overweight and obese women, while this sex difference was not observed in patients treated with ACEI or ARBs. In conclusion, our results indicate that elevated RMR per kg of LBM may be normalized by antagonizing the renin-angiotensin system

Cerebral blood flow, frontal lobe oxygenation and intra-arterial blood pressure during sprint exercise in normoxia and severe acute hypoxia in humans

Cerebral blood flow (CBF) is regulated to secure brain O2 delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O2 delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (PIO2 = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min(-1), mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced PETCO2, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO2 in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO2 in hypoxia, leading to a similar brain O2 delivery during the sprints regardless of PIO2. In conclusion, when a conflict exists between preserving brain O2 delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O2 delivery

Cerebral blood flow, frontal lobe oxygenation and intra-arterial blood pressure during sprint exercise in normoxia and severe acute hypoxia in humans

Cerebral blood flow (CBF) is regulated to secure brain O2 delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O2 delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (PIO2 = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min(-1), mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced PETCO2, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO2 in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO2 in hypoxia, leading to a similar brain O2 delivery during the sprints regardless of PIO2. In conclusion, when a conflict exists between preserving brain O2 delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O2 delivery

Enhancement of Exercise Performance by 48 Hours, and 15-Day Supplementation with Mangiferin and Luteolin in Men

The natural polyphenols mangiferin and luteolin have free radical-scavenging properties, induce the antioxidant gene program and down-regulate the expression of superoxide-producing enzymes. However, the effects of these two polyphenols on exercise capacity remains mostly unknown. To determine whether a combination of luteolin (peanut husk extract containing 95% luteolin, PHE) and mangiferin (mango leave extract (MLE), Zynamite&#174;) at low (PHE: 50 mg/day; and 140 mg/day of MLE containing 100 mg of mangiferin; L) and high doses (PHE: 100 mg/day; MLE: 420 mg/day; H) may enhance exercise performance, twelve physically active men performed incremental exercise to exhaustion, followed by sprint and endurance exercise after 48 h (acute effects) and 15 days of supplementation (prolonged effects) with polyphenols or placebo, following a double-blind crossover design. During sprint exercise, mangiferin + luteolin supplementation enhanced exercise performance, facilitated muscle oxygen extraction, and improved brain oxygenation, without increasing the VO2. Compared to placebo, mangiferin + luteolin increased muscle O2 extraction during post-exercise ischemia, and improved sprint performance after ischemia-reperfusion likely by increasing glycolytic energy production, as reflected by higher blood lactate concentrations after the sprints. Similar responses were elicited by the two doses tested. In conclusion, acute and prolonged supplementation with mangiferin combined with luteolin enhances performance, muscle O2 extraction, and brain oxygenation during sprint exercise, at high and low doses

Impact of data averaging strategies on V̇O2max assessment: Mathematical modeling and reliability

Background: No consensus exists on how to average data to optimize VO2max assessment. Although the VO2max value is reduced with larger averaging blocks, no mathematical procedure is available to account for the effect of the length of the averaging block on VO2max. Aims: To determine the effect that the number of breaths or seconds included in the averaging block has on the VO2max value and its reproducibility and to develop correction equations to standardize VO2max values obtained with different averaging strategies. Methods: Eighty‐four subjects performed duplicate incremental tests to exhaustion (IE) in the cycle ergometer and/or treadmill using two metabolic carts (Vyntus and Vmax N29). Rolling breath averages and fixed time averages were calculated from breath‐by‐breath data from 6 to 60 breaths or seconds. Results: VO2max decayed from 6 to 60 breath averages by 10% in low fit (VO2max 0.97). There was a linear‐log relationship between the number of breaths or seconds in the averaging block and VO2max (R2 > 0.99, P < 0.001), and specific equations were developed to standardize VO2max values to a fixed number of breaths or seconds. Reproducibility was higher in trained than low‐fit subjects and not influenced by the averaging strategy, exercise mode, maximal respiratory rate, or IE protocol. Conclusions: The VO2max decreases following a linear‐log function with the number of breaths or seconds included in the averaging block and can be corrected with specific equations as those developed here

Angiotensin-converting enzyme 2 (SARS-CoV-2 receptor) expression in human skeletal muscle

The study aimed to determine the levels of skeletal muscle angiotensin-converting enzyme 2 (ACE2, the SARS-CoV-2 receptor) protein expression in men and women and assess whether ACE2 expression in skeletal muscle is associated with cardiorespiratory fitness and adiposity. The level of ACE2 in vastus lateralis muscle biopsies collected in previous studies from 170 men (age: 19–65 years, weight: 56–137 kg, BMI: 23–44) and 69 women (age: 18–55 years, weight: 41–126 kg, BMI: 22–39) was analyzed in duplicate by western blot. VO2max was determined by ergospirometry and body composition by DXA. ACE2 protein expression was 1.8-fold higher in women than men (p = 0.001, n = 239). This sex difference disappeared after accounting for the percentage of body fat (fat %), VO2max per kg of legs lean mass (VO2max-LLM) and age (p = 0.47). Multiple regression analysis showed that the fat % (β = 0.47) is the main predictor of the variability in ACE2 protein expression in skeletal muscle, explaining 5.2% of the variance. VO2max-LLM had also predictive value (β = 0.09). There was a significant fat % by VO2max-LLM interaction, such that for subjects with low fat %, VO2max-LLM was positively associated with ACE2 expression while as fat % increased the slope of the positive association between VO2max-LLM and ACE2 was reduced. In conclusion, women express higher amounts of ACE2 in their skeletal muscles than men. This sexual dimorphism is mainly explained by sex differences in fat % and cardiorespiratory fitness. The percentage of body fat is the main predictor of the variability in ACE2 protein expression in human skeletal muscle