Biology subjects

Le Blanc, O.

Publications and source records attributed to Le Blanc, O..

4 recordsLinked to original sources

bioRxiv2019

Dynamic cerebral autoregulation of endurance-trained men following 6 weeks of high-intensity interval training to exhaustion

Elevated cardiorespiratory fitness (CRF) is associated with reduced dynamic cerebral autoregulation (dCA), but the impact of exercise training per se on dCA remains equivocal. In addition, resting cerebral blood flow (CBF) and dCA after high-intensity interval training (HIIT) in individuals with already high CRF is unknown. We examined to what extent 6 weeks of HIIT affect resting CBF and dCA in cardiorespiratory fit men and explored if potential changes are intensity-dependent. Endurance-trained men were assigned to group HIIT85 (85% of maximal aerobic power, 1 to 7 min effort bouts, n = 8) and HIIT115 (115% of maximal aerobic power, 30 s to 1 min effort bouts, n = 9). Training sessions were completed until exhaustion 3 times/week over 6 weeks. Mean arterial pressure (MAP) and middle cerebral artery mean blood velocity (MCAvmean) were measured continuously at rest and during repeated squat-stands (0.05 and 0.10 Hz). Transfer function analysis (TFA) was used to characterize dCA on driven blood pressure oscillations during repeated squat-stands. Neither training nor intensity had an effect on resting MAP and MCAvmean (both P > 0.05). TFA phase during 0.10 Hz squat-stands decreased after HIIT irrespective of intensity (HIIT85: 0.77 {+/-} 0.22 vs. 0.67 {+/-} 0.18 radians; HIIT115: pre: 0.62 {+/-} 0.19 vs. post: 0.59 {+/-} 0.13 radians, time effect P = 0.048). These results suggest that HIIT over 6 weeks have no apparent benefits on resting CBF, but a subtle attenuation in dCA is seen posttraining irrespective of intensity training in endurance-trained men.\n\nNEW & NOTEWORTHYThe novel findings of this study are that 6 weeks of submaximal and supramaximal high-intensity interval exercise to exhaustion reduce dynamic cerebral autoregulation irrespective of training intensity in endurance-trained men. However, these HIIT protocols do not influence resting cerebral blood flow in these individuals. The results indicate the cerebrovasculature of endurance-trained men has an attenuated ability to react to large and rapid changes in blood pressure following HIIT.

physiology↗

bioRxiv2019

Cardiac remodeling after six weeks of high-intensity interval training to exhaustion in endurance-trained males

High-intensity interval training (HIIT) improves physical performance of endurance athletes, although studies examining its cardiovascular effects are sparse. We evaluated the impact of HIIT on blood pressure, heart rate and cardiac cavities size and function in endurance-trained adults. Seventeen endurance-trained males underwent 24-hour ambulatory blood pressure monitoring (ABPM) and Doppler echocardiography at baseline and after 6 weeks of HIIT. Participants were divided in 2 groups (85% maximal aerobic power (MP); HIIT85, n=8 and 115% MP; HIIT115, n = 9) in order to compare the impact of different HIIT intensities. ABPM and cardiac chambers size and function were similar between groups at baseline. HIIT reduced heart rate (55 {+/-} 8 vs. 51 {+/-} 7 bpm; p= 0.003), systolic blood pressure (SBP; 121 {+/-} 11 vs 118 {+/-} 9 mmHg; p = 0.01), mean arterial pressure (MAP; 90 {+/-} 8 vs 89 {+/-} 6 mmHg; p = 0.03) and pulse pressure (52 {+/-} 6 vs 49 {+/-} 5 mmHg; p = 0.01), irrespective of training intensity. Left atrium (LA) volumes increased after HIIT (maximal: 50 {+/-} 14 vs 54 {+/-}14 ml; p= 0.02; minimal: 15 {+/-} 5 vs 20 {+/-} 8 ml; p = 0.01) in both groups. Right ventricle (RV) global longitudinal strain lowered after training in the HIIT85 group only (20 {+/-} 4 vs. 17 {+/-} 3%, p = 0.04). In endurance-trained males, six weeks of HIIT reduce SBP and MAP and increase LA volumes irrespective of training intensity, whereas submaximal HIIT deteriorates RV systolic function.\n\nKey pointsO_LIHigh-intensity interval training improves physical performance of endurance athletes, although studies examining its cardiovascular effects are sparse.\nC_LIO_LIWe evaluated the impact of submaximal (85% maximal aerobic power) and supramaximal (115% maximal aerobic power) high-intensity interval training on ambulatory blood pressure, heart rate and cardiac cavities size and function in endurance-trained adults.\nC_LIO_LIIrrespective of training intensity, six weeks of high-intensity interval training increase left atrial volumes in endurance-trained adults, whereas the submaximal training decreases right ventricular systolic function.\nC_LIO_LIThese results may help identify the exercise threshold for potential toxicity of intense exercise training for at-risk individuals and ideal exercise training regimens conferring optimal cardiovascular protection and adapted endurance training for athletes.\nC_LI

physiology↗

bioRxiv2018

Functional implications of impaired dynamic cerebral autoregulation in young healthy women; a comparative investigation

Women exhibit higher prevalence of orthostatic hypotension with presyncopal symptoms compared to men. These symptoms could be influenced by an attenuated ability of the cerebrovasculature to respond to rapid changes in blood pressure (BP) [dynamic cerebral autoregulation (dCA)]. However, the influence of sex on dCA remains equivocal. We compared dCA in 11 women (25 {+/-} 2 y) and 11 age-matched men (24 {+/-} 1 y) using a multimodal approach including a sit-to-stand maneuver and forced oscillations (5 min of squat-stand performed at 0.05 and 0.10 Hz). The prevalence of initial orthostatic hypotension (IOH; decrease in systolic [≥] 40 mmHg and/or diastolic BP [≥] 20 mmHg) during the first 15 sec of sit-to-stand was determined as a functional outcome. In women, the decrease in mean middle cerebral artery blood velocity (MCAvmean) following the sit-to-stand was greater (-20 {+/-} 8 vs. -11 {+/-} 7 cm sec-1; p=0.018) and the onset of the regulatory change (time lapse between the beginning of the sit-to-stand and the increase in the conductance index (MCAvmean/mean arterial pressure(MAP)) was delayed (p=0.007). Transfer function analysis gain during 0.05 Hz squat-stand was [~]48% higher in women (6.4 {+/-} 1.3 vs. 3.8 {+/-} 2.3 sec; p=0.017). The prevalence of IOH was comparable between groups (4/9 vs. 5/9, p=0.637). These results indicate the cerebrovasculature of healthy women has an attenuated ability to react to large and rapid changes in BP in the face of preserved orthostasis, which could be related to a higher cerebrovascular reserve to face a rapid transient hypotension.\n\nNEWS & NOTEWORTHYThe novel findings of this study are that healthy women have impaired dynamic cerebral autoregulation, although the prevalence of orthostatic intolerance was similar in women and men. These results indicate the cerebrovasculature of healthy women has an attenuated ability to react to large and rapid changes in blood pressure in the face of preserved orthostasis, which could be related to a higher cerebrovascular reserve to face a rapid transient hypotension.

physiology↗

bioRxiv2017

Diminished dynamic cerebral autoregulatory capacity with forced oscillations in mean arterial pressure with elevated cardiorespiratory fitness

The effect that cardiorespiratory fitness has on the dynamic cerebral autoregulatory capacity during changes in mean arterial pressure (MAP) remains equivocal. Using a multiple-metrics approach, challenging MAP across the spectrum of physiological extremes (i.e. spontaneous through forced MAP oscillations), we characterized dynamic cerebral autoregulatory capacity in 19 male endurance athletes and 8 controls via three methods: [1] onset of regulation (i.e., time delay before an increase in middle cerebral artery (MCA) conductance [MCA flow velocity (MCAv)/mean arterial pressure (MAP)] and rate of regulation, after transient hypotension induced by sit-to-stand, and transfer function analysis (TFA) of MAP and MCAv responses during [2] spontaneous and [3] forced oscillations (5-min of squat-stand maneuvers performed at 0.05 and 0.10 Hz). Reductions in MAP and mean MCAv (MCAVmean) during initial orthostatic stress (0-30 s after sit-to-stand) and the prevalence of orthostatic hypotension were also determined. Onset of regulation was delayed after sit-to-stand in athletes (3.1{+/-}1.7 vs. 1.5{+/-}1.0 s; p=0.03), but rate of regulation was not different between groups (0.24{+/-}0.05 vs. 0.21{+/-}0.09 s-1; p=0.82). While both groups had comparable TFA metrics during spontaneous oscillations, athletes had higher TFA gain during 0.10 Hz squat-stand vs. recreational controls (p=0.01). Reductions in MAP (p=0.15) and MCAVmean (p=0.11) during orthostatic stress and the prevalence of initial orthostatic hypotension (p=0.65) were comparable between groups. These results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in MAP in individuals with elevated cardiorespiratory fitness.\n\nNew findingsO_ST_ABSWhat is the central question of this study?C_ST_ABSO_LIWhat is the impact of cardiorespiratory fitness on dynamic cerebral autoregulatory capacity?\nC_LI\n\nWhat is the main finding and its importance?O_LIOur results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in mean arterial pressure in individuals with elevated cardiorespiratory fitness.\nC_LI

physiology↗