Hypobaric Hypoxic Conditions Research Articles

Global REACH 2018: The Effect of an Expiratory Resistance Mask with Dead Space on Sleep and Acute Mountain Sickness During Acute Exposure to Hypobaric Hypoxia.

Carr, Jay, Rachel Stone, Courtney Tymko, Kaitlyn Tymko, Geoff B. Coombs, Ryan L. Hoiland, Connor A. Howe, Michael M. Tymko, Philip N. Ainslie, and Alexander Patrician. Global REACH 2018: the effect of an expiratory resistance mask with dead space on sleep and acute mountain sickness during acute exposure to hypobaric hypoxia. High Alt Med Biol. 21:297-302, 2020. We hypothesized that an expiratory resistance and dead space (ER/DS) mask, a version of which was previously shown to partially alleviate sleep-disordered breathing and headache severity during acute normobaric hypoxia (Patrician et al.), would exhibit similar results in conditions of hypobaric hypoxia. In a randomized, single-blinded, sham-controlled, and sex-matched design, 31 healthy lowlanders rapidly (6-8 hours) ascended from sea level to 4300 m (Cerro de Pasco, Peru) and slept with either an ER/DS mask (n = 15) or sham mask (n = 16). Sleep was assessed (via WatchPAT) and questionnaires collected before sleep and upon waking the morning after. There was no difference in apnea-hypopnea index (AHI) between the ER/DS (77 ± 20 events/h) or sham mask (84 ± 27 events/h; p = 0.57). In addition, there was no alleviation of headache scores, improvement in sleep quality, or acute mountain sickness symptom severity. Both the sham and ER/DS masks were poorly tolerated (∼50% subject noncompliance in both groups). These findings highlight the importance and necessity of field-testing and demonstrate that more testing is needed before ER/DS devices, such as these, can be recommended for prophylactic benefits at high altitude.

Influence of individual psychological features on the functional state of aviation specialists in conditions of hypobaric hypoxia

The study is devoted to the study of the influence of individual psychological characteristics of the personality of aviation specialists on the tolerability of moderate degrees of hypobaric hypoxia, simulated in a pressure chamber. The study included the assessment of physiological parameters (blood pressure, heart rate, arterial blood saturation, Roufier index) and psychophysiological indicators (critical frequency of light flickering fusion, complex sensorimotor response, indicators of subjective assessment of the state (SAN test)) depending on the level of neuroticism, extroversion and personal anxiety level.
 As a result of the study, it was found that the functional state of the body of subjects with high levels of neuroticism in hypobaric hypoxia changes significantly than in subjects with low levels of neuroticism, which is confirmed by a more pronounced decrease in health, activity and mood by 17.5% (p 0.01), 16.9% (p 0.05) and 9% (p 0.01), respectively, an increase in the time of complex sensorimotor response by 12.6% (p 0.01), as well as more pronounced functional changes in the cardiovascular system.
 It was revealed that changes in some physiological parameters in extroverts had a large negative dynamics in hypoxia, so the increase in the Roufier index in the group of introverts at 30, 60 minutes and after the rise by 97.3%, 98.6% and 15.1%, respectively, against an increase of 118.2%, 123.6% and 16.4% in the group of extroverts was revealed. In the group of extroverts, an increase in the time of complex sensorimotor response after the end of the study was found by 8.0% (p 0.05), an increase in critical frequency of light flickering fusion compared to the indicators obtained before the rise by 5.2% (p 0.05).
 It is established that the functional status of subjects with high levels of trait anxiety had a more pronounced negative trend in terms of the effects of hypobaric hypoxia, which is confirmed by a significant higher values of the Roufier index in groups with high levels of trait anxiety, with the background study, 30th, 60th minute and after rising; extending the time complex sensorimotor response to 45 minute 6.1% (p 0.05), and after altitude study by 9.5% (p 0.01); by the 40th minute of stay in the hyperbaric chamber the indicators of well-being decreased by 20.3% (p 0.01), activity by 18.8% (p 0.05) and mood by 13.7% (p 0.01).
 Thus, it was shown that in assessing the tolerability of moderate degrees of hypoxia, it is necessary to take into account the dependence of changes in the functional state of the organism on individual psychological characteristics.

Effects of an Acute Pilates Program under Hypoxic Conditions on Vascular Endothelial Function in Pilates Participants: A Randomized Crossover Trial.

This study aimed to compare the effects of an acute Pilates program under hypoxic vs. normoxic conditions on the metabolic, cardiac, and vascular functions of the participants. Ten healthy female Pilates experts completed a 50-min tubing Pilates program under normoxic conditions (N trial) and under 3000 m (inspired oxygen fraction = 14.5%) hypobaric hypoxia conditions (H trial) after a 30-min exposure in the respective environments on different days. Blood pressure, branchial ankle pulse wave velocity, and flow-mediated dilation (FMD) in the branchial artery were measured before and after the exercise. Metabolic parameters and cardiac function were assessed every minute during the exercise. Both trials showed a significant increase in FMD; however, the increase in FMD was significantly higher after the H trial than that after the N trial. Furthermore, FMD before exercise was significantly higher in the H trial than in the N trial. In terms of metabolic parameters, minute ventilation, carbon dioxide excretion, respiratory exchange ratio, and carbohydrate oxidation were significantly higher but fat oxidation was lower during the H trial than during the N trial. In terms of cardiac function, heart rate was significantly increased during the H trial than during the N trial. Our results suggested that, compared to that under normoxic conditions, Pilates exercise under hypoxic conditions led to greater metabolic and cardiac responses and also elicited an additive effect on vascular endothelial function.

Hypoxic Training Is Beneficial in Elite Athletes.

There is no doubt that many hypoxic conditions or prolonged exposures to altitude result in “biological costs of hypoxic adaptations that outweigh their benefits” (1), particularly in endurance athletes exposed to a) exercise-induced arterial hypoxemia leading to a larger decrease in VO2max and aerobic endurance; b) increased sympathetic activity and decreased baroreflex sensitivity; and c) increased pulmonary arterial pressure. There is also no doubt that sleeping in moderate altitude (2000-3000 m) as performed by the athletes using either live high-train high (LHTH) or live high-train low (LHTL) methods leads to periodic breathing, intermittent hypoxia (IH) and increase in desaturation periods; e.g. 3% oxygen desaturation index, but to a larger extent in hypobaric hypoxia (HH, real altitude) than in normobaric hypoxia (NH, simulated altitude), as shown at 2250 m (2). The three main questions debated in the present contrasting perspective are however different: 1. Are there any evidences showing if the “counteracting maladaptation” (reported above) outweigh the benefits of the different hypoxic methods at short- or long-term in elite athletes? ; 2. Are there any robust data supporting that hypoxic training is beneficial in elite athletes? ; 3. Contradictory, are there robust data showing that hypoxic training is not beneficial in elite athletes?

The Dynamics of Human Physical Performance in the Hypobaric Hypoxia Conditions Based on the Individual Psychological Characteristics

This study focuses on the investigation of the effects of flight factors, including the hypobaric hypoxia, on physical performance based on the individual psychological profile. The goal of the study was to evaluate the association between the endurability of the flight factors and individual psychological features. Physical performance was assessed using the Ruffier test in three stages: during the recording of the baseline data, when ascending to an altitude of 5000 m in a hypobaric chamber, and after the ascent. The data obtained were analyzed considering the individual psychological features, including the neuroticism, extroversion, and trait anxiety. The levels of neuroticism and extroversion were evaluated using the Eysenck Personality Questionnaire, and trait anxiety was assessed using Spielberger’s tests in the modification of Khanin. It has been found that individuals with a high neuroticism level are characterized by a more significant decrease in myocardial work capacity by 17.3% (p < 0.05) on the 30th minute and by 23.4% (р < 0.01) on the 60th minute of ascent in the hypobaric chamber compared to the subjects with a low neuroticism level. The results of the analysis of the Ruffier test have demonstrated 2.16-fold (р < 0.01) and 2.25-fold (р < 0.01) increase in the Ruffier index by the 30th and 60th minutes of the ascent in the altitude chamber, respectively, in the individuals characterized by an initially 28% lower (р < 0.05) baseline Ruffier index compared to those with high level of trait anxiety. Comparison of the indices of the myocardial work capacity during ascent has shown that heart work capacity in the group of introverts decreased by 20.0% (p < 0.05) by the 30th minute of being in a hypobaric chamber compared to the group of extroverts; by the 60th minute, the difference was 17.8% (р < 0.01). Therefore, it has been demonstrated that the association between the myocardial work capacity and individual psychological characteristics should be considered in the evaluation of the tolerance to moderate hypoxia.

Influence of Natural Hypobaric Hypoxic Conditions on Dynamic Visual Performance.

Background: Both dynamic and static visual performances are essential for safety and motoric performance at altitude. There is a lack of information regarding alterations in dynamic visual performance (DVP) in oxygen-reduced environments. The purpose of this study was to analyze DVP in natural hypoxic conditions in a group of young, healthy hikers. Methods: DVP in four parafoveal subfields was analyzed using the computer-assisted Düsseldorf Test for Dynamic Vision. Measurements were performed twice at altitudes above 3500 m during an 8-day alpine hike. Results: On day 5 (3647 m), no changes in DVP were detected. On day 6 (4554 m), however, we found a significant reduction in DVP in the superior parafoveal retinal subfield, partly representing the lower visual field. The observed changes did not correlate with oxygen saturation, hematocrit, or cardiovascular parameters. We found no interrelation between symptoms of acute mountain sickness and DVP at altitude. Conclusions: Our data suggest that hiking at altitudes above 4500 m results in lower DVP in the visual field of healthy young people. The alteration might affect motor performance and coordination, increasing the risk of accidents.

Effects of dietary nitrate supplementation on microvascular physiology at 4559 m altitude – A randomised controlled trial (Xtreme Alps)

Native highlanders (e.g. Sherpa) demonstrate remarkable hypoxic tolerance, possibly secondary to higher levels of circulating nitric oxide (NO) and increased microcirculatory blood flow. As part of the Xtreme Alps study (a randomised placebo-controlled trial of dietary nitrate supplementation under field conditions of hypobaric hypoxia), we investigated whether dietary supplementation with nitrate could improve NO availability and microvascular blood flow in lowlanders. Plasma measurements of nitrate, nitrite and nitroso species were performed together with measurements of sublingual (sidestream dark-field camera) and forearm blood flow (venous occlusion plethysmography) in 28 healthy adult volunteers resident at 4559 m for 1 week; half receiving a beetroot-based high-nitrate supplement and half receiving an identically-tasting low nitrate ‘placebo’. Dietary supplementation increased plasma nitrate concentrations 4-fold compared to the placebo group, both at sea level (SL; 19.2 vs 76.9 μM) and at day 5 (D5) of high altitude (22.9 vs 84.3 μM, p < 0.001). Dietary nitrate supplementation also significantly increased both plasma nitrite (0.78 vs. 0.86 μM SL, 0.31 vs. 0.41 μM D5, p = 0.03) and total nitroso product (11.3 vs. 19.7 nM SL, 9.7 vs. 12.3 nM D5, p < 0.001) levels both at sea level and at 4559 m. However, plasma nitrite concentrations were more than 50% lower at 4559 m compared to sea level in both treatment groups. Despite these significant changes, dietary nitrate supplementation had no effect on any measured read-outs of sublingual or forearm blood flow, even when environmental hypoxia was experimentally reversed using supplemental oxygen. In conclusion, dietary nitrate supplementation does not improve microcirculatory function at 4559 m.

Effect of chronic intermittent hypobaric hypoxia on heart rate variability in conscious rats

To examine the effect of chronic intermittent hypobaric hypoxia (CIHH) on heart rate variability (HRV), male adult Sprague Dawley rats were exposed to hypoxia (oxygen 11.1%) in a hypobaric chamber for 42days, 6hours each day, simulating an altitude of 5000m. The body weight and blood pressure of rats were recorded once a week, electrocardiograms were analyzed continuously using biotelemetry, before, during and after CIHH treatment each day, and HRV was evaluated using spectrum analysis. No significant difference of body weight and blood pressure was found between CIHH and control rats. After 4weeks of CIHH treatment, total power (TP) and very low-frequency component (VLF) were lower in CIHH rats than in control rats under hypobaric hypoxia condition. During CIHH treatment, low frequency (LF) was higher in 1 week and lower in 5-6weeks in CIHH rats than control rats under hypobaric hypoxia, but not normoxic conditions. The high-frequency component (HF) was not changed during CIHH treatment, so LF/HF increased initially, and then recovered under the hypobaric hypoxia condition following 3weeks of CIHH treatment. In addition, the HR was increased in CIHH rats after 4weeks of CIHH treatment compared with control rats. Furthermore, HRV was altered significantly in control rats, but not in CIHH rats exposed to acute normobaric hypoxia. These data suggest that CIHH treatment modulates cardiac autonomic activity adaptively and inhibits the acute normobaric hypoxia-induced changes in HRV.

Determining the Operating Costs of a Medical Surveillance Program for Copper Miners Exposed to High Altitude–Induced Chronic Intermittent Hypoxia in Chile Using a Combination of Microcosting and Time-Driven Activity-Based Costing

BackgroundCopper mining installations in Chile use a large number of workers who do their jobs at high altitudes, exposing them to the conditions of chronic intermittent hypobaric hypoxia. The Chilean Safety Association implements the surveillance program. ObjectiveThis organization, under the sponsorship of the Chilean Superintendency of Social Security, was interested in determining the costs involved in this program to support its decision-making processes and to improve its performance. MethodsDirect operating costs of the Hypoxia Medical Surveillance Program were determined through on-site surveys applied to the organization’s local agencies in charge. The microcosting method was used, quantifying personnel costs, consumables, and equipment and overhead costs. Time-driven activity-based costing was partially adapted for the allocation of personnel and equipment costs. Costs concerning activities, groups of activities and items, and average cost per exposed worker were determined. ResultsThe annual costs of the program were $127 299.58. The highest costs corresponded to the assessment activities, which were $89 192.13, representing 60.06% of the total. The labor factor costs were $77 568.50, which represents 60.93% of the total. The average cost per worker in the program is $21.17. ConclusionsThe partial adaptation of the time-driven activity-based costing method in combination with the microcosting method provides a suitable solution to determine the total costs of running a healthcare program of this kind. The information generated by this study will aid in the decision-making and management processes of the Hypoxia Medical Surveillance Program.

Variation of Cognitive Function During a Short Stay at Hypobaric Hypoxia Chamber (Altitude: 3842 M).

ObjectiveTo observe the effects of a fast-acute ascent to high altitude on brain cognitive function and transcranial doppler parameters in order to understand the physiological countermeasures of hypoxia.Methods17 high-altitude-naïve male subjects (mean age was 26.3 ± 8.1 years) participated in the study. We measured Critical Flicker Fusion Frequency (CFFF), blood oxygen saturation, Psychology Experiment Building (PEBL) including three tests (Modified Math Processing Task, Perceptual Vigilance Task, and Time Estimation Task), as well as Cerebral Blood Flow index (CBFi), mean cerebral artery Systolic and diastolic velocities, Cerebral Pulsatility index (CPi), and heart Rate. All were measured at sea level, at least 1 h after arrival at the hypobaric hypoxia equivalent of 3842 m and 1 h after return to sea level.ResultsUnder acute exposure to hypobaric hypoxic conditions, significant decrease in CFFF [42.1 ± 1 vs. 43.5 ± 1.7 Hz at sea level (asl), p < 0.01], CBFi (611 ± 51 vs. 665 ± 71 asl, p < 0.01) and blood oxygen saturation (83 ± 4% vs. 98 ± 1% asl, p < 0.001) as compared to pre-ascent values were observed. Physiological countermeasures to hypoxia could be involved as there was no significant change in neuropsychometric tests, Systolic and Diastolic velocities and CPi. A significant increase in Heart Rate (81 ± 15 bpm vs. 66 ± 15 bpm asl, p < 0.001) was observed. All parameters returned to their basal values 1 h after regaining sea level.ConclusionHypoxia results in a decrease in CFFF, CBFi and oxygen saturation and in an increase in heart rate. As it decreased, Cerebral Blood Flow index does not seem to be the physiological measurement of choice to hypoxia explaining the maintenance of cognitive performance after acute exposure to hypobaric hypoxia and requires further investigation. Cerebral oxygen delivery and extraction could be one of the underlying mechanisms.

Separate and combined influences of heat and hypobaric hypoxia on self-paced aerobic exercise performance.

Heat and hypobaric hypoxia independently compromise exercise performance; however, their combined impact on exercise performance has yet to be quantified. This study examined the effects of heat, hypobaric hypoxia, and the combination of these environments on self-paced cycling time trial (TT) performance. Twelve subjects [2 female, 10 male; sea level (SL) peak oxygen consumption (V̇o2peak), 41.5 ± 4.4 mL·kg-1·min-1, mean ± SD] completed 30 min of steady-state cycling exercise (50% SL V̇o2peak), followed by a 15-min self-paced TT in four environmental conditions: SL thermoneutral [SLTN; 250 m, 20°C, 30-50% relative humidity (rh)], SL hot (SLH; 250 m, 35°C, 30% rh), hypobaric hypoxia thermoneutral (HTN; 3,000 m, 20°C, 30-50% rh), and hypobaric hypoxia hot (HH; 3,000 m, 35°C, 30% rh). Performance was assessed by the total work (kJ) completed. TT performance was lower (P < 0.05) in SLH, HTN, and HH relative to SLTN (-15.4 ± 9.7, -24.1 ± 16.2, and -33.1 ± 13.4 kJ, respectively). Additionally, the total work completed in HTN and HH was lower (P < 0.05) than that in SLH. In SLH, HTN, and HH, work rate was reduced versus SLTN (P < 0.05) within the first 3 min of exercise and was consistent for the remainder of the bout. No differences (P > 0.05) existed for heart rate or Ratings of Perceived Exertion at the end of exercise among conditions. The decrease in self-paced TT performance in the heat and/or hypobaric hypoxia conditions compared with SLTN conditions resulted from a nearly immediate reduction in work rate that may have been regulated by environmentally induced changes in physiological strain and perception of effort in response to TT exercise.NEW & NOTEWORTHY This is the first known study to examine the combined effects of heat and hypobaric hypoxia on short-duration self-paced cycling time trial performance. Regardless of environmental condition, subjects utilized an even work rate for the entire duration of the time trial. The presence of both environmental stressors led to a greater performance impairment than heat or hypobaric hypoxia alone, and the performance decrement stemmed from an early reduction of work rate.

Mild Hypobaric Hypoxia Enhances Post-exercise Vascular Responses in Young Male Runners.

It has been reported that sustained post-exercise vasodilation may be linked to exercise-induced angiogenesis. The present study aimed to evaluate whether mild hypobaric hypoxia enhances the post-exercise reduction in systemic vascular resistance in young male runners. Seven male intercollegiate runners (aged 19–21 years) performed maximal incremental treadmill running under conditions of hypobaric hypoxia (corresponding to 2,200 m above sea level, hereinafter referred to as HH) and normobaric normoxia (corresponding to sea level, hereinafter referred to as NN). A third exercise test was performed under NN conditions, consisting of submaximal exercise with the same absolute exercise volume as was achieved during HH (submaximal exercise under NN conditions, hereinafter referred to as NNsubmax). Blood pressure and cardiac output (CO) were measured before and at 15, 30, and 60 (p60) minutes after exercise. Compared with NN, exercise time was shorter in HH and NNsubmax conditions (p < 0.05). Systolic blood pressure and mean blood pressure (MBP) were lower after exercise in HH conditions (p < 0.05). No condition-related differences were found in CO. Total peripheral resistance (TPR, defined as the ratio of MBP to CO) was significantly lower after exercise compared to baseline for all conditions (p < 0.05). However, the decrease in TPR was maintained longer after exercise in HH compared with NN and NNsubmax conditions (p < 0.05). At p60, TPR was lower than baseline for HH conditions (p < 0.05), whereas after exercise in NN, and NNsubmax conditions, TPR recovered to baseline by p60. Decreases in systemic vascular resistance after exercise were maintained longer under mild HH conditions compared with NN despite the lower exercise volume of the former.

COMPARATIVE ANALYSIS OF ACTOPROTECTIVE PROPERTIES OF NEW CHEMICAL COMPOUNDS

Aim. This study was aimed at searching and investigating new substances among phenylethyl derivatives of 3-hydroxypyridine, which exhibit a high actoprotective activity under the conditions of normoxia and acute hypobaric hypoxia.Materials and methods. New compounds of phenylethyl derivatives of 3-hydroxypyridine under the SC code (n = 23) were investigated in comparison with bemethyl and bromantane. The actoprotective activity of new compounds was assessed in experimental animals using a treadmill running test under the conditions of normoxia and acute hypobaric hypoxia. The studied chemical substances and comparative drugs were administered 1 hour prior to exposure of animals to the test. Statistical processing of the obtained experimental results was performed using Microsoft Excel and Statistica for Windows 6.0 software.Results. Among the studied substances, active compounds exhibiting an actoprotective effect have been distinguished. SC-119 chemical substance was revealed, which exceeds the other studied chemicals and bemethyl and bromantane reference actoprotectors in terms of the range of effective doses and actoprotective activity under the conditions of normoxia and acute hypobaric hypoxia.Conclusion. According to the results of the study, the SC-119 compound seems to be a prospective candidate for further research into highly effective actoprotective drugs.

Short- and middle-term high-altitude exposure does not affect visual acuity and contrast sensitivity of healthy young people

ObjectiveVisual acuity and contrast sensitivity are crucial for optimal performance and safe sport activity. From a practical sport-specific perspective, visual performance is obligatory for orientation and movement control in mountainous areas. The purpose of this study was to analyze the effect of hypobaric hypoxic conditions on visual acuity and contrast sensitivity of short-term and middle-term acclimatized healthy young people. DesignThis study used a repeated-measure design with ten eye-healthy and physically active students representing different types of sports. MethodsWith the help of a computer-based Landolt C and a Sine Wave Contrast test, visual performance was investigated similar before (156 m), during a nine-day high-altitude sojourn (sleeping level: 890–4640 m), and three months later (156 m). All tests were performed under standardized illumination conditions. Additionally, morning blood oxygen saturation, hematocrits, hemoglobin, body mass, and self-reported symptoms of acute mountain sickness criteria were determined. ResultsWhole blood oxygen saturation declined during altitude exposure. The analysis of central visual performance at altitude showed no effect of hypobaric hypoxia. ConclusionOur data suggest that activity in a hypobaric hypoxia condition at moderate to high altitude levels of up to 4600 m does not affect visual acuity and contrast sensitivity of acclimatized healthy young people. However, in contrast to previous studies that outlined acutely impaired central visual performance with respect to hypoxia, we suggest that acclimatization might induce adaptation of visual perception performance and therefore reduce the risk of accidents resulting from partial loss of visual performance at altitude.

The Impact of Altitude on Sleep-Related Breathing Disorders in Infants and Children

Millions of children worldwide reside at or sojourn to high-altitude locales and are therefore subjected to hypobaric hypoxic conditions. Such exposure is known to impact respiratory physiology including determinants of sleep-related breathing disorders (SRBDs). This review aims to summarize emerging data on the effects of high altitude on SRBDs in infants and children, to highlight possible pathophysiologic consequences of these effects, and to outline specific topics requiring further investigation. Recent findings demonstrate that intermediate and high-altitude conditions increase central and obstructive respiratory event frequency both in healthy infants and children and in those with symptoms of sleep-disordered breathing. These changes are most pronounced in infancy and in symptomatic children. Exposure to high altitude degrades cognitive performance and increases cardiovascular morbidity. Genetic factors which vary between specific populations modulate the high-altitude response and therefore limit the generalizability of these findings. High-altitude exposure worsens SRBD prevalence and severity when implementing scoring rules and diagnostic criteria developed at low altitude. Whether these changes in polysomnographic parameters contribute to the adverse cardiovascular and neurocognitive outcomes observed in high-altitude residents is of critical importance and requires further study.

Expiratory flow limitation under moderate hypobaric hypoxia does not influence ventilatory responses during incremental running in endurance runners.

We tested whether expiratory flow limitation (EFL) occurs in endurance athletes in a moderately hypobaric hypoxic environment equivalent to 2500 m above sea level and, if so, whether EFL inhibits peak ventilation (V˙Epeak), thereby exacerbating the hypoxia‐induced reduction in peak oxygen uptake (V˙O2peak). Seventeen young male endurance runners performed incremental exhaustive running on separate days under hypobaric hypoxic (560 mmHg) and normobaric normoxic (760 mmHg) conditions. Oxygen uptake (V˙O2), minute ventilation (V˙E), arterial O2 saturation (SpO2), and operating lung volume were measured throughout the incremental exercise. Among the runners tested, 35% exhibited EFL (EFL group, n = 6) in the hypobaric hypoxic condition, whereas the rest did not (Non‐EFL group, n = 11). There were no differences between the EFL and Non‐EFL groups for V˙Epeak and V˙O2peak under either condition. Percent changes in V˙Epeak (4 ± 4 vs. 2 ± 4%) and V˙O2peak (−18 ± 6 vs. −16 ± 6%) from normobaric normoxia to hypobaric hypoxia also did not differ between the EFL and Non‐EFL groups (all P > 0.05). No differences in maximal running velocity, SpO2, or operating lung volume were detected between the two groups under either condition. These results suggest that under the moderate hypobaric hypoxia (2500 m above sea level) frequently used for high‐attitude training, ~35% of endurance athletes may exhibit EFL, but their ventilatory and metabolic responses during maximal exercise are similar to those who do not exhibit EFL.

Nutritional strategies in an elite wheelchair marathoner at 3900\u2009m altitude: a case report

BackgroundAltitude training is a common practice among middle-distance and marathon runners. During acclimatization, sympathetic drive may increase resting metabolic rate (RMR), therefore implementation of targeted nutritional interventions based on training demands and environmental conditions becomes paramount. This single case study represents the first nutritional intervention performed under hypobaric hypoxic conditions (3900 m) in Paralympic sport. These results may elucidate the unique nutritional requirements of upper body endurance athletes training at altitude.Case presentationThis case study examined the effects of a nutritional intervention on the body mass of a 36-year-old professional wheelchair athlete (silver medalist at the Paralympic Games and 106 victories in assorted road events) during a five-week altitude training camp, divided into pre-altitude at sea level (BN), acclimatization to altitude (Puno, 3860 m) (BH), specific training (W1,2,3,4) and return to sea level (Post) phases. Energy intake (kcal) and body mass (kg) were recorded daily. Results demonstrated significant decrease in body mass between BN and BH (52.6 ± 0.4 vs 50.7 ± 0.5 kg, P < 0.001) which returned to pre-altitude values, upon returning to sea level at Post (52.1 ± 0.5 kg). A greater daily intake was observed during BH (2899 ± 670 kcal) and W1,2,3 (3037 ± 490; 3116 ± 170; 3101 ± 385 kcal) compared to BN (2397 ± 242 kcal, P < 0.01) and Post (2411 ± 137 kcal, P < 0.01). No differences were reported between W4 (2786 ± 375 kcal), BN and Post. The amount of carbohydrates ingested (g · kg− 1) was greater in W1,2,3, (9.6 ± 2.1; 9.9 ± 1.2; 9.6 ± 1.2) than in BN (7.1 ± 1.2) and Post (6.3 ± 0.8, P < 0.001). Effect sizes (Cohen’s d) for all variables relative to BN (all time points) exceed a large effect (d > 0.80).ConclusionsThese results suggest an elite wheelchair marathoner training at 3860 m required increased nutrient requirements as well as the systematic control needed to re-adapt a nutritional program. Moreover, our findings highlight training and nutritional prescription optimization of elite wheelchair athletes, under challenging environmental conditions.

Effect of Playing and Training at Altitude on Concussion Incidence in Professional Football.

Background:Despite the increased attention to sports-related concussion, the literature lacks information about the environmental factors that contribute to concussion incidence. Previous investigators have noted a decreased rate of concussion in football games played at higher altitude.Purpose/Hypothesis:The purpose of this study was to investigate whether the protective effects of altitude on concussion rate, as described by previous investigators, were due to acute effects of altitude exposure or chronic adaptations to training at altitude. Our hypothesis was that these protective effects are not attributable to relative cerebral edema that occurs in conditions of altitude-associated hypobaric hypoxia, known as the “slosh effect,” but rather result from long-term adaptations to training at altitude.Study Design:Descriptive epidemiology study.Methods:Athletes from the 2012, 2013, 2014, and 2015 National Football League (NFL) seasons were included in this analysis of publicly available data. Concussion rates were subdivided into 4 groups: (1) low-altitude teams playing below 644 feet (low-low), (2) low-altitude teams playing above 644 feet (low-high), (3) high-altitude teams playing below 644 feet (high-low), and (4) high-altitude teams playing above 644 feet (high-high).Results:Away teams had a significantly higher rate of concussion (0.32 concussions per exposure) compared with their home team counterparts (0.27 concussions per exposure; P = .03). Teams training and playing at high altitude had a 28% decreased concussion rate, which was significantly lower compared with concussion incidence rates for overall, low-low, and high-low groups (P < .05). In comparison, teams that trained at altitude but played below 644 feet had the highest rate of concussion, at 0.36 concussions per exposure (P < .05).Conclusion:These data indicate that living and training at altitude may have a protective effect on concussion rate, as evidenced by the significant reduction in the high-high group and the lack of an effect in the low-high group. However, teams from low altitude playing at high altitude did not have a statistically significant reduction in concussion rate. These results show that the slosh theory does not completely explain the effects of altitude on concussion incidence rate in the NFL. Further analyses are needed to investigate the true cause of altitude-induced protection in the NFL.

Melatonin Supplementation Under Hypobaric Hypoxia and Hypothermia Conditions

The presence of oxidative and nitrosative stress under hypobaric hypoxia and hypothermia conditions led us to experimentally study the effect of the administration of melatonin as a non-nutritional antioxidant in rats. Morphological changes in the lungs and heart were monitored under hypobaric hypoxia and hypothermia conditions, with and without melatonin supplementation. Melatonin partially corrected the changes induced by hypothermia in the lungs and by hypoxia in the myocardium.

Hypobaric Hypoxia Induces Autophagy of Umbilical Cord Mesenchymal Stem Cells

To investigate the autophagy activity changes of umbilical cord mesenchymal cells (MSC) under hypobaric hypoxia and the effect of hypobaric hypoxia on cell viability. Umbilical cord mesenchymal cells were cultured in the chamber of hypobaric hypoxia with an air pressure of 41.1 kPa and an oxygen density of 1%. At 0, 4, 8, 16, 24 and 48 hours, the cells were harvested for Western blot and real-time PCR to observe the expression level of the autophagy marker protein LC3B. And the cell viability under hypobaric hypoxia was evaluated after treatment with autophagy inhibitors HCQ (8 μg/ml) and 3MA (5 mmol/L). LC3B expression in MSC at protein and mRNA levels were up-regulated significantly after being cultured under hypobaric hypoxia condition for 8 hours. And compared with the control group, inhibition of autophagy reduced cell viability while increased Caspase-3 expression and the incidence of apoptosis. Hypobaric hypoxia activates autophagy in MSC, and the activation of autophagy might play a protective role for cell survival.