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.

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.

Knee angle-dependent oxygen consumption during isometric contractions of the knee extensors determined with near-infrared spectroscopy

2005 ◽  
Vol 99 (2) ◽  
pp. 579-586 ◽  
Author(s):  
C. J. de Ruiter ◽  
M. D. de Boer ◽  
M. Spanjaard ◽  
A. de Haan
Keyword(s):  
Oxygen Consumption ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Rectus Femoris ◽  
Knee Extensors ◽  
Isometric Contractions ◽  
Knee Angle ◽  
Extensor Muscles ◽  
Knee Extensor Muscles

Fatigue resistance of knee extensor muscles is higher during voluntary isometric contractions at short compared with longer muscle lengths. In the present study we hypothesized that this would be due to lower energy consumption at short muscle lengths. Ten healthy male subjects performed isometric contractions with the knee extensor muscles at a 30, 60, and 90° knee angle (full extension = 0°). At each angle, muscle oxygen consumption (mV̇o2) of the rectus femoris, vastus lateralis, and vastus medialis muscle was obtained with near-infrared spectroscopy. mV̇o2 was measured during maximal isometric contractions and during contractions at 10, 30, and 50% of maximal torque capacity. During all contractions, blood flow to the muscle was occluded with a pressure cuff (450 mmHg). mV̇o2 significantly ( P < 0.05) increased with torque and at all torque levels, and for each of the three muscles mV̇o2 was significantly lower at 30° compared with 60° and 90° and mV̇o2 was similar ( P > 0.05) at 60° and 90°. Across all torque levels, average (± SD) mV̇o2 at the 30° angle for vastus medialis, rectus femoris, and vastus lateralis, respectively, was 70.0 ± 10.4, 72.2 ± 12.7, and 75.9 ± 8.0% of the average mV̇o2 obtained for each torque at 60 and 90°. In conclusion, oxygen consumption of the knee extensors was significantly lower during isometric contractions at the 30° than at the 60° and 90° knee angle, which probably contributes to the previously reported longer duration of sustained isometric contractions at relatively short muscle lengths.

Effects of respiratory muscle unloading on leg muscle oxygenation and blood volume during high-intensity exercise in chronic heart failure

2008 ◽  
Vol 294 (6) ◽  
pp. H2465-H2472 ◽  
Author(s):  
Audrey Borghi-Silva ◽  
Cláudia Carrascosa ◽  
Cristino Carneiro Oliveira ◽  
Adriano C. Barroco ◽  
Danilo C. Berton ◽  
...  
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Chronic Heart Failure ◽  
Blood Volume ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Oxygenation Index ◽  
Assisted Ventilation ◽  
Muscle Oxygenation ◽  
Leg Muscle

Blood flow requirements of the respiratory muscles (RM) increase markedly during exercise in chronic heart failure (CHF). We reasoned that if the RM could subtract a fraction of the limited cardiac output (QT) from the peripheral muscles, RM unloading would improve locomotor muscle perfusion. Nine patients with CHF (left ventricle ejection fraction = 26 ± 7%) undertook constant-work rate tests (70-80% peak) receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes (Δ%) in deoxy-hemoglobyn, oxi-Hb ([O2Hb]), tissue oxygenation index, and total Hb ([HbTOT], an index of local blood volume) in the vastus lateralis were measured by near infrared spectroscopy. In addition, QT was monitored by impedance cardiography and arterial O2 saturation by pulse oximetry (SpO2). There were significant improvements in exercise tolerance (Tlim) with PAV. Blood lactate, leg effort/Tlim and dyspnea/Tlim were lower with PAV compared with sham ventilation ( P < 0.05). There were no significant effects of RM unloading on systemic O2 delivery as QT and SpO2 at submaximal exercise and at Tlim did not differ between PAV and sham ventilation ( P > 0.05). Unloaded breathing, however, was related to enhanced leg muscle oxygenation and local blood volume compared with sham, i.e., higher Δ[O2Hb]% and Δ[HbTOT]%, respectively ( P < 0.05). We conclude that RM unloading had beneficial effects on the oxygenation status and blood volume of the exercising muscles at similar systemic O2 delivery in patients with advanced CHF. These data suggest that blood flow was redistributed from respiratory to locomotor muscles during unloaded breathing.

Factors contributing to lower metabolic demand of eccentric compared with concentric cycling

2017 ◽  
Vol 123 (4) ◽  
pp. 884-893 ◽  
Author(s):  
Luis Peñailillo ◽  
Anthony J. Blazevich ◽  
Kazunori Nosaka
Keyword(s):  
Oxygen Consumption ◽  
Muscle Activity ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Oxygenation Index ◽  
Metabolic Cost ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Metabolic Demand ◽  
Length Changes

This study compared muscle-tendon behavior, muscle oxygenation, and muscle activity between eccentric and concentric cycling exercise at the same work output to investigate why metabolic demand is lower during eccentric cycling than with concentric cycling. Eleven untrained men (27.1 ± 7.0 y) performed concentric cycling (CONC) and eccentric cycling (ECC) for 10 min (60 rpm) at 65% of the maximal concentric cycling power output (191 ± 45 W) 4 wk apart. During cycling, oxygen consumption (V̇o2), heart rate (HR), vastus lateralis (VL) tissue total hemoglobin (tHb), and oxygenation index (TOI) were recorded, and muscle-tendon behavior was assessed using ultrasonography. The surface electromyogram (EMG) was recorded from VL, vastus medialis (VM), rectus femoris (RF), and biceps femoris (BF) muscles, and cycling torque and knee joint angle during each revolution were also recorded. Average V̇o2 (−65 ± 7%) and HR (−35 ± 9%) were lower and average TOI was greater (16 ± 1%) during ECC than CONC, but tHb was similar between bouts. Positive and negative cycling peak crank torques were greater (32 ± 21 and 48 ± 24%, respectively) during ECC than CONC, but muscle-tendon unit and fascicle and tendinous tissue length changes during pedal revolutions were similar between CONC and ECC. VL, VM, RF, and BF peak EMG amplitudes were smaller (24 ± 15, 22 ± 18, 16 ± 17, and 18 ± 9%, respectively) during ECC than CONC. These results suggest that the lower metabolic cost of eccentric compared with concentric cycling was due mainly to a lower level of muscle activation per torque output. NEW & NOTEWORTHY This study shows that lower oxygen consumption of eccentric compared with concentric cycling at the same workload is explained by lower muscle activity of agonist and antagonist muscles during eccentric compared with during concentric cycling.

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 The effects of lumbar sympathectomy on bone and soft tissue haemodynamics of the leg recorded using near infrared spectroscopy: A case report

2016 ◽  
Vol 3 (1) ◽  
pp. 28
Author(s):  
Robert M Meertens ◽  
Karen M Knapp ◽  
Francesco Casanova ◽  
William D Strain
Keyword(s):  
Infrared Spectroscopy ◽  
Case Report ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Haemoglobin Concentration ◽  
Arterial Occlusion ◽  
Oxygenation Index ◽  
Lumbar Sympathectomy ◽  
Intervertebral Fusion ◽  
Concentration Changes

Near infrared spectroscopy (NIRS) is an established tool for the measurement of microvascular haemodynamics in different tissue types.  This case report outlines the novel use of NIRS for measuring total oxygenation index (TOI) and relative oxygenated and deoxygenated haemoglobin concentration changes as markers of oxygenation and blood volume in muscle and bone tissue.  In particular, NIRS is used to examine differences between the left and right leg in a participant who has experienced a permanent unilateral lumbar sympathectomy following an anterior lumbar intervertebral fusion.  Anatomical sites at the lateral head of the gastrocnemius, tibial diaphysis and proximal tibia were investigated with NIRS during an arterial occlusion protocol at the distal femur.  Consistent differences were observed between the sympathectomised left leg and the normal right leg.  These included reduced baseline TOI, reduced deoxygenation rates during occlusion, and reduced reoxygenation rates post occlusion release in the sympathectomised leg at all anatomical sites.  This case report demonstrates the potential of NIRS as a research tool for investigating the microvascular effects of lumbar sympathectomy.  This may be useful for further investigation into the merit of chemical lumbar sympathectomy for the treatment of a variety of conditions, including hyperhidrosis and peripheral vascular disease.

scholarly journals Cerebral Fractional Oxygen Extraction is Inversely Correlated with Oxygen Delivery in the Sick, Newborn, Preterm Infant

2005 ◽  
Vol 25 (5) ◽  
pp. 545-553 ◽  
Author(s):  
Christopher M Kissack ◽  
Rosaline Garr ◽  
Stephen P Wardle ◽  
A Michael Weindling
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Preterm Infants ◽  
Metabolic Activity ◽  
Negative Correlation ◽  
Oxygen Delivery ◽  
Near Infrared ◽  
Extremely Low Birth Weight ◽  
Oxygen Extraction ◽  
Cerebral Oxygen

Cerebral blood flow (CBF) is known to be low in newborn infants, but this has not been shown to be damaging. The purpose of this study was to investigate the relationships between cerebral haemoglobin flow, blood flow, oxygen delivery, oxygen consumption, venous saturation, and fractional oxygen extraction (OEF) in newborn, preterm infants. Measurements were made by near-infrared spectroscopy in 13 very preterm, extremely low birth weight infants (median gestation 25 weeks) during the first 3 days after birth. There was a negative correlation between cerebral oxygen delivery and OEF ( n=13, r=−0.5, P=0.03), which implies that when there is a reduction in cerebral oxygen delivery in sick preterm infants, increased cerebral oxygen extraction may be responsible for maintaining oxygen availability to the brain. During the first 3 days after birth CBF ( n=13, r=0.7, P=0.01), oxygen delivery ( n=13, r=0.5, P=0.03), and oxygen consumption ( n=13, r=0.7, P=0.004) all increased. This increase in oxygen consumption indicates increased cerebral metabolic activity after birth, which is likely to be a normal adaptation to extrauterine life. The increases in blood flow and oxygen delivery may also be normal adaptations that facilitate this increase in metabolic activity. There was a decrease ( P=0.04) in mean (±s.d.) cerebral OEF between day 1 (0.37±0.10) and day 2 (0.29±0.09), with no change between day 2 and day 3. Taking into account the negative correlation between OEF and oxygen delivery, this decrease in OEF may be because of increased oxygen delivery during this time.

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