Dietary nitrate improves muscle but not cerebral oxygenation status during exercise in hypoxia

2012 ◽  
Vol 113 (5) ◽  
pp. 736-745 ◽  
Author(s):  
Evi Masschelein ◽  
Ruud Van Thienen ◽  
Xu Wang ◽  
Ann Van Schepdael ◽  
Martine Thomis ◽  
...  
Keyword(s):  
Exercise Tolerance ◽  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Acute Mountain Sickness ◽  
Oxygenation Index ◽  
Whole Body ◽  
Time To Exhaustion ◽  
Dietary Nitrate ◽  
Nitrate Supplementation ◽  
Oxygenation Status

Exercise tolerance is impaired in hypoxia, and it has recently been shown that dietary nitrate supplementation can reduce the oxygen (O2) cost of muscle contractions. Therefore, we investigated the effect of dietary nitrate supplementation on arterial, muscle, and cerebral oxygenation status, symptoms of acute mountain sickness (AMS), and exercise tolerance at simulated 5,000 m altitude. Fifteen young, healthy volunteers participated in three experimental sessions according to a crossover study design. From 6 days prior to each session, subjects received either beetroot (BR) juice delivering 0.07 mmol nitrate/kg body wt/day or a control drink (CON). One session was in normoxia with CON (NORCON); the two other sessions were in hypoxia (11% O2), with either CON (HYPCON) or BR (HYPBR). Subjects first cycled for 20 min at 45% of peak O2 consumption (VO2peak; EX45%) and thereafter, performed a maximal incremental exercise test (EXmax). Whole-body VO2, arterial O2 saturation (%SpO2) via pulsoximetry, and tissue oxygenation index of both muscle (TOIM) and cerebral (TOIC) tissue by near-infrared spectroscopy were measured. Hypoxia per se substantially reduced VO2peak, %SpO2, TOIM, and TOIC (NORCON vs. HYPCON, P < 0.05). Compared with HYPCON, VO2 at rest and during EX45% was lower in HYPBR ( P < 0.05), whereas %SpO2 was higher ( P < 0.05). TOIM was ∼4-5% higher in HYPBR than in HYPCON both at rest and during EX45% and EXmax ( P < 0.05). TOIC as well as the incidence of AMS symptoms were similar between HYPCON and HYPBR at any time. Hypoxia reduced time to exhaustion in EXmax by 36% ( P < 0.05), but this ergolytic effect was partly negated by BR (+5%, P < 0.05). Short-term dietary nitrate supplementation improves arterial and muscle oxygenation status but not cerebral oxygenation status during exercise in severe hypoxia. This is associated with improved exercise tolerance against the background of a similar incidence of AMS.

scholarly journals Cerebral Hemodynamic and Ventilatory Responses to Hypoxia, Hypercapnia, and Hypocapnia during 5 Days at 4,350 m

2013 ◽  
Vol 34 (1) ◽  
pp. 52-60 ◽  
Author(s):  
Thomas Rupp ◽  
François Esteve ◽  
Pierre Bouzat ◽  
Carsten Lundby ◽  
Stéphane Perrey ◽  
...  
Keyword(s):  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Acute Mountain Sickness ◽  
Oxygenation Index ◽  
Short Term ◽  
Ventilatory Responses ◽  
Altitude Exposure ◽  
Total Hemoglobin ◽  
Tissue Oxygenation Index ◽  
Mountain Sickness

This study investigated the changes in cerebral near-infrared spectroscopy (NIRS) signals, cerebrovascular and ventilatory responses to hypoxia and CO2 during altitude exposure. At sea level (SL), after 24 hours and 5 days at 4,350 m, 11 healthy subjects were exposed to normoxia, isocapnic hypoxia, hypercapnia, and hypocapnia. The following parameters were measured: prefrontal tissue oxygenation index (TOI), oxy- (HbO2), deoxy- and total hemoglobin (HbTot) concentrations with NIRS, blood velocity in the middle cerebral artery (MCAv) with transcranial Doppler and ventilation. Smaller prefrontal deoxygenation and larger ΔHbTot in response to hypoxia were observed at altitude compared with SL (day 5: ΔHbO2−0.6±1.1 versus −1.8±1.3  μmol/cmper mm Hg and ΔHbTot 1.4±1.3 versus 0.7±1.1  μmol/cm per mm Hg). The hypoxic MCAv and ventilatory responses were enhanced at altitude. Prefrontal oxygenation increased less in response to hypercapnia at altitude compared with SL (day 5: ΔTOI 0.3±0.2 versus 0.5±0.3% mm Hg). The hypercapnic MCAv and ventilatory responses were decreased and increased, respectively, at altitude. Hemodynamic responses to hypocapnia did not change at altitude. Short-term altitude exposure improves cerebral oxygenation in response to hypoxia but decreases it during hypercapnia. Although these changes may be relevant for conditions such as exercise or sleep at altitude, they were not associated with symptoms of acute mountain sickness.

scholarly journals Dietary nitrate supplementation attenuates the reduction in exercise tolerance following blood donation

2016 ◽  
Vol 311 (6) ◽  
pp. H1520-H1529 ◽  
Author(s):  
Sinead T. J. McDonagh ◽  
Anni Vanhatalo ◽  
Jonathan Fulford ◽  
Lee J. Wylie ◽  
Stephen J. Bailey ◽  
...  
Keyword(s):  
Exercise Tolerance ◽  
Peak Power ◽  
Blood Donation ◽  
Hemoglobin Concentration ◽  
Moderate Intensity ◽  
Beetroot Juice ◽  
Moderate Intensity Exercise ◽  
Exercise Tests ◽  
Dietary Nitrate ◽  
Nitrate Supplementation

We tested the hypothesis that dietary nitrate (NO3−)-rich beetroot juice (BR) supplementation could partially offset deteriorations in O2transport and utilization and exercise tolerance after blood donation. Twenty-two healthy volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and following withdrawal of ∼450 ml of whole blood. Before donation, all subjects consumed seven 70-ml shots of NO3−-depleted BR [placebo (PL)] in the 48 h preceding the exercise tests. During the 48 h after blood donation, subjects consumed seven shots of BR (each containing 6.2 mmol of NO3−, n = 11) or PL ( n = 11) before repeating the exercise tests. Hemoglobin concentration and hematocrit were reduced by ∼8–9% following blood donation ( P < 0.05), with no difference between the BR and PL groups. Steady-state O2uptake during moderate-intensity exercise was ∼4% lower after than before donation in the BR group ( P < 0.05) but was unchanged in the PL group. The ramp test peak power decreased from predonation (341 ± 70 and 331 ± 68 W in PL and BR, respectively) to postdonation (324 ± 69 and 322 ± 66 W in PL and BR, respectively) in both groups ( P < 0.05). However, the decrement in performance was significantly less in the BR than PL group (2.7% vs. 5.0%, P < 0.05). NO3−supplementation reduced the O2cost of moderate-intensity exercise and attenuated the decline in ramp incremental exercise performance following blood donation. These results have implications for improving functional capacity following blood loss.

scholarly journals Effects of respiratory muscle endurance training on cerebral oxygenation and hemodynamics, and effort perceptions during maximal exercise

2020 ◽  
Author(s):  
◽  
Johnna Somerville
Keyword(s):  
Endurance Training ◽  
Respiratory Muscle ◽  
Perceived Exertion ◽  
Near Infrared ◽  
Maximal Exercise ◽  
Cerebral Oxygenation ◽  
Primary Objective ◽  
Muscle Endurance ◽  
Time To Exhaustion ◽  
Respiratory Muscle Endurance

The primary objective of this study was to investigate the effects of a 4-week respiratory muscle endurance training (eRMT) program on the physiological and psychological aspects of central fatigue using, respectively, near-infrared spectroscopy (NIRS) and quantification of effort perceptions during maximal exercise. A secondary objective was to assess any impact of eRMT on respiratory health and exercise performance. This study compared pre- and post-eRMT data from the same group of healthy adults. The results indicated that eRMT did not have any effect on respiratory function, exercise time to exhaustion, or physiological responses to exercise but significantly decreased ratings of perceived exertion (RPE) during exercise. An increase in the concentrations of oxygenated hemoglobin [O2Hb], deoxygenated hemoglobin [HHb], and total hemoglobin [tHb] during exercise was observed post-eRMT compared to pre-eRMT, and this increase differed by hemisphere. Based on these preliminary findings, we suggest an eRMTinduced left-to-right hemodynamic shift during exercise, consistent with the change from a novel to a learned task.

Enhanced muscular oxygen extraction in athletes exaggerates hypoxemia during exercise in hypoxia

2016 ◽  
Vol 120 (3) ◽  
pp. 351-361 ◽  
Author(s):  
Ruud Van Thienen ◽  
Peter Hespel
Keyword(s):  
Oxygen Consumption ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Acute Mountain Sickness ◽  
Maximal Oxygen Consumption ◽  
Arterial Occlusion ◽  
Oxygenation Index ◽  
High Rate ◽  
Oxygen Extraction ◽  
Mountain Sickness

High rate of muscular oxygen utilization facilitates the development of hypoxemia during exercise at altitude. Because endurance training stimulates oxygen extraction capacity, we investigated whether endurance athletes are at higher risk to developing hypoxemia and thereby acute mountain sickness symptoms during exercise at simulated high altitude. Elite athletes (ATL; n = 8) and fit controls (CON; n = 7) cycled for 20 min at 100 W (EX100W), as well as performed an incremental maximal oxygen consumption test (EXMAX) in normobaric hypoxia (0.107 inspired O2 fraction) or normoxia (0.209 inspired O2 fraction). Cardiorespiratory responses, arterial Po2 (PaO2), and oxygenation status in m. vastus lateralis [tissue oxygenation index (TOIM)] and frontal cortex (TOIC) by near-infrared spectroscopy, were measured. Muscle O2 uptake rate was estimated from change in oxyhemoglobin concentration during a 10-min arterial occlusion in m. gastrocnemius. Maximal oxygen consumption in normoxia was 70 ± 2 ml·min−1·kg−1 in ATL vs. 43 ± 2 ml·min−1·kg−1 in CON, and in hypoxia decreased more in ATL (−41%) than in CON (−25%, P < 0.05). Both in normoxia at PaO2 of ∼95 Torr, and in hypoxia at PaO2 of ∼35 Torr, muscle O2 uptake was twofold higher in ATL than in CON (0.12 vs. 0.06 ml·min−1·100 g−1; P < 0.05). During EX100W in hypoxia, PaO2 dropped to lower ( P < 0.05) values in ATL (27.6 ± 0.7 Torr) than in CON (33.5 ± 1.0 Torr). During EXMAX, but not during EX100W, TOIM was ∼15% lower in ATL than in CON ( P < 0.05). TOIC was similar between the groups at any time. This study shows that maintenance of high muscular oxygen extraction rate at very low circulating PaO2 stimulates the development of hypoxemia during submaximal exercise in hypoxia in endurance-trained individuals. This effect may predispose to premature development of acute mountain sickness symptoms during exercise at altitude.

Effect Of Dietary Nitrate Supplementation On The Development Of Neuromuscular Fatigue During Whole Body Exercise

2017 ◽  
Vol 49 (5S) ◽  
pp. 1090-1091
Author(s):  
Taylor S. Thurston ◽  
Thomas J. Hureau ◽  
Joshua C. Weavil ◽  
Jayson R. Gifford ◽  
Hsuan-Yu Wan ◽  
...  
Keyword(s):  
Neuromuscular Fatigue ◽  
Whole Body ◽  
Dietary Nitrate ◽  
Nitrate Supplementation

Frontal cortical oxygenation changes during gravity-induced loss of consciousness in humans: a near-infrared spatially resolved spectroscopic study

2007 ◽  
Vol 103 (4) ◽  
pp. 1326-1331 ◽  
Author(s):  
Koichi Kurihara ◽  
Azusa Kikukawa ◽  
Asao Kobayashi ◽  
Toshio Nakadate
Keyword(s):  
High Performance ◽  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Oxygenation Index ◽  
Loss Of Consciousness ◽  
Spatially Resolved ◽  
Hemoglobin Saturation ◽  
Significant Difference ◽  
Concentration Changes ◽  
Spatially Resolved Spectroscopy

Gravity (G)-induced loss of consciousness (G-LOC), which is presumably caused by a reduction of cerebral blood flow resulting in a decreased oxygen supply to the brain, is a major threat to pilots of high-performance fighter aircraft. The application of cerebral near-infrared spectroscopy (NIRS) to monitor gravity-induced cerebral oxygenation debt has generated concern over potential sources of extracranial contamination. The recently developed NIR spatially resolved spectroscopy (SRS-NIRS) has been confirmed to provide frontal cortical tissue hemoglobin saturation [tissue oxygenation index (TOI)]. In this study, we monitored the TOI and the standard NIRS measured chromophore concentration changes of oxygenated hemoglobin and deoxygenated hemoglobin in 141 healthy male pilots during various levels of +Gz (head-to-foot inertial forces) exposure to identify the differences between subjects who lose consciousness and those who do not during high +Gz exposure. Subjects were exposed to seven centrifuge profiles, with +Gz levels from 4 to 8 Gz and an onset rate from 0.1 to 6.0 Gz/s. The SRS-NIRS revealed an ∼15% decrease in the TOI in G-LOC. The present study also demonstrated the TOI to be a useful variable to evaluate the effect of the anti-G protection system. However, there was no significant difference found between conditions with and without G-LOC in subjects with terminated G exposure. Further studies that elucidate the mechanism(s) behind the wide variety of individual differences may be needed for a method of G-LOC prediction to be effectively realized.

scholarly journals Dynamics of cortical oxygenation during immediate adaptation to extrauterine life

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Léa Leroy ◽  
Mahdi Mahmoudzadeh ◽  
Jean Gondry ◽  
Arthur Foulon ◽  
Fabrice Wallois
Keyword(s):  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Oxygenation Index ◽  
Perinatal Period ◽  
Multiple Strategies ◽  
The Status ◽  
Tissue Oxygenation Index ◽  
Term Newborns ◽  
Lactate Levels ◽  
Index Value

AbstractThe neonatal transition involves physiological modifications as a consequence of the complexity of the perinatal period. Various strategies can be used to attain the same level of postnatal cerebral oxygenation, depending on the status of the infant at birth. We evaluated such strategies by recording 20 full-term newborns by near-infrared spectroscopy during the first 10 min of life. The acid–base status at birth revealed two clustered profiles of cerebral oxygenation dynamics. Lower pH and base excess and higher lactate levels were associated with more rapid attainment of the 95% maximal tissue oxygenation index value. These results suggest that metabolic mechanisms drive initial cerebral oxygenation dynamics during this critical period. These results confirm the capacity of newborns to develop multiple strategies to protect the brain.

scholarly journals Effect of diaphragm fatigue on subsequent exercise tolerance in healthy men and women

2018 ◽  
Vol 125 (6) ◽  
pp. 1987-1996 ◽  
Author(s):  
Joseph F. Welch ◽  
Bruno Archiza ◽  
Jordan A. Guenette ◽  
Christopher R. West ◽  
A. William Sheel
Keyword(s):  
Exercise Test ◽  
Exercise Tolerance ◽  
Inspiratory Muscle ◽  
Whole Body ◽  
Time To Exhaustion ◽  
Men And Women ◽  
Muscle Metaboreflex ◽  
Healthy Men ◽  
Pressure Threshold ◽  
Diaphragmatic Fatigue

Women are more resistant to diaphragmatic fatigue (DF) and experience an attenuated inspiratory muscle metaboreflex relative to men. The effects of such sex-based differences on whole body exercise tolerance are yet to be examined. It was hypothesized that DF induced prior to exercise would cause less of a reduction in subsequent exercise time in women compared to men. Healthy men ( n = 9, age = 24 ± 3 yr) and women ( n = 9, age = 24 ± 3 yr) completed a maximal incremental cycle test on day 1. On day 2, subjects performed isocapnic inspiratory pressure-threshold loading (PTL) to task failure followed by a constant load submaximal time-to-exhaustion (TTE) exercise test at 85% of the predetermined peak work rate. On day 3, subjects performed the same exercise test without prior induced DF. Days 2 and 3 were randomized and counterbalanced. Magnetic stimulation of the phrenic nerve roots was used to nonvolitionally assess DF by measurement of transdiaphragmatic twitch pressure ( Pdi,tw). A similar degree of DF was produced in both sexes following PTL [ Pdi,tw (% change from baseline): M = −24.6 ± 7.8%, W = −23.1 ± 5.4%; P = 0.54)]. There was a significant reduction in TTE with prior induced DF compared with the control condition in both men (10.9 ± 3.5 min vs. 13.0 ± 3.2 min, P = 0.05) and women (10.1 ± 2.4 min vs. 12.2 ± 3.3 min, P = 0.03) that did not differ in magnitude between the sexes (M = −15.8 ± 19.5%, W = −14.5 ± 19.2%, P = 0.89). In conclusion, DF negatively and equally impairs exercise tolerance independent of sex. NEW & NOTEWORTHY Women are more resistant to diaphragmatic fatigue (DF) relative to men. The effect of DF on exercise tolerance is currently being debated. Our findings show that DF negatively and equally affects exercise tolerance in healthy men and women. Mechanisms beyond the inspiratory muscle metaboreflex (e.g., dyspnea, central fatigue, breathing pattern) may explain the absence of a sex-based difference.

Maintained cerebral oxygenation during maximal self-paced exercise in elite Kenyan runners

2015 ◽  
Vol 118 (2) ◽  
pp. 156-162 ◽  
Author(s):  
J. Santos-Concejero ◽  
F. Billaut ◽  
L. Grobler ◽  
J. Oliván ◽  
T. D. Noakes ◽  
...  
Keyword(s):  
Near Infrared ◽  
Ventilatory Threshold ◽  
Cerebral Oxygenation ◽  
Oxygenation Index ◽  
Time Trial ◽  
Stable Range ◽  
Long Distance ◽  
Speed Test ◽  
Long Distance Running ◽  
Concentration Changes

The purpose of this study was to analyze the cerebral oxygenation response to maximal self-paced and incremental exercise in elite Kenyan runners from the Kalenjin tribe. On two separate occasions, 15 elite Kenyan distance runners completed a 5-km time trial (TT) and a peak treadmill speed test (PTS). Changes in cerebral oxygenation were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxyhemoglobin (Δ[O2Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI). During the 5-km TT (15.2 ± 0.2 min), cerebral oxygenation increased over the first half (increased Δ[O2Hb] and Δ[HHb]) and, thereafter, Δ[O2Hb] remained constant (effect size, ES = 0.33, small effect), whereas Δ[HHb] increased until the end of the trial ( P < 0.05, ES = 3.13, large effect). In contrast, during the PTS, from the speed corresponding to the second ventilatory threshold, Δ[O2Hb] decreased ( P < 0.05, ES = 1.51, large effect), whereas Δ[HHb] continued to increase progressively until exhaustion ( P < 0.05, ES = 1.22, large effect). Last, the TOI was higher during the PTS than during the 5-km TT ( P < 0.001, ES = 3.08; very large effect), whereas nTHI values were lower ( P < 0.001, ES = 2.36, large effect). This study shows that Kenyan runners from the Kalenjin tribe are able to maintain their cerebral oxygenation within a stable range during a self-paced maximal 5-km time trial, but not during an incremental maximal test. This may contribute to their long-distance running success.

Sign in / Sign up

Export Citation Format

Share Document