Energy Intake of Men With Excess Weight During Normobaric Hypoxic Confinement

Due to the observations of weight loss at high altitude, normobaric hypoxia has been considered as a method of weight loss in obese individuals. With this regard, the aim of the present study was to determine the effect of hypoxia per se on metabolism in men with excess weight. Eight men living with excess weight (125.0 ± 17.7 kg; 30.5 ± 11.1 years, BMI: 37.6 ± 6.2 kg⋅m–2) participated in a randomized cross-over study comprising two 10-day confinements: normobaric (altitude of facility ≃ 940 m) normoxia (NORMOXIA; PIO2 = 133 mmHg), and normobaric hypoxia (HYPOXIA). The PIO2 in the latter was reduced from 105 (simulated altitude of 2,800 m) to 98 mmHg (simulated altitude of 3,400 m over 10 days. Before, and at the end of each confinement, participants completed a meal tolerance test (MTT). Resting energy expenditure (REE), circulating glucose, GLP-1, insulin, catecholamines, ghrelin, peptide-YY (PYY), leptin, gastro-intestinal blood flow, and appetite sensations were measured in fasted and postprandial states. Fasting REE increased after HYPOXIA (+358.0 ± 49.3 kcal⋅day–1, p = 0.03), but not after NORMOXIA (−33.1 ± 17.6 kcal⋅day–1). Postprandial REE was also significantly increased after HYPOXIA (p ≤ 0.05), as was the level of PYY. Furthermore, a tendency for decreased energy intake was concomitant with a significant body weight reduction after HYPOXIA (−0.7 ± 0.2 kg) compared to NORMOXIA (+1.0 ± 0.2 kg). The HYPOXIA trial increased the metabolic requirements, with a tendency toward decreased energy intake concomitant with increased PYY levels supporting the notion of a hypoxia-induced appetite inhibition, that could potentially lead to body weight reduction. The greater postprandial blood-glucose response following hypoxic confinement, suggests the potential development of insulin resistance.

CRITERIA FOR PREDICTING BIOELECTRICAL PROCESSES IN THE HUMAN HEART UNDER VARIOUS STAGES OF ACUTE HYPOXIA

Despite much available information on the heart activity under acute normobaric hypoxia (ANH), there are no data on the leading ECG components and the criteria for predicting their deviations at various stages of ANH and depending on its duration. The aim of the paper is to determine the leading ECG components and the dependence of their deviations on the initial parameters at different stages of acute normobaric hypoxia and depending on its duration in a healthy person. Materials and Methods. The shifts in parameter indicators were determined in two groups of men (aged 18–26) under 20-minute mild (14.5 % O2, n1=30) and medium (12.3 % O2, n2=29) ANH. During the study the authors used 7 ECG parameters and oximetry. Statistica 10.0 software package was used for data processing. The authors determined normality of distribution, they also used factor analysis, correlation, and regression. Results. For all ANH degrees, the leading factor included QT, T1II, and (with one exception) RR. In case of mild ANH, the 1st factor was supplemented by P1II at the 5th minute of exposure, and in case of medium ANH at the 20th minute. The second most important factor in case of mild ANH was determined by BAR and RII at the 5th and 20th min and by BAR at the 10th min. In case of medium ANH it was supplemented by P1II at the 5th min, by RII and BAR at the 10th min, and by BAL at the 20th min. It was shown that in case of mild ANH P1II, RII, BAR, and RR deviations reliably depend on the initial parameters; for medium ANH, such dependence is observed for RR and QT at the 5th and 10th min, for RII at the 10th and 20th min, and for P1II at the 20th min. Conclusion. The main markers of heart bioelectrical processes under ANH are QT, T1II and RR, other parameters are variable. The availability to predict deviations of ECG parameters by their initial parameters depends on ANH stage. Key words: human, hypoxia, oximetry, electrocardiography, factorial, correlation, regression analysis. Несмотря на имеющиеся многочисленные сведения о деятельности сердца при острой нормобарической гипоксии (ОНГ), данные о ведущих компонентах ЭКГ и критериях прогнозирования их отклонений при разной степени ОНГ и в зависимости от ее длительности отсутствуют. Цель работы – определить ведущие компоненты ЭКГ и зависимости их отклонений от исходных величин при разных степенях острой нормобарической гипоксии и в зависимости от её длительности у здорового человека. Материалы и методы. С помощью ЭКГ (7 параметров) и оксигемометрии определены сдвиги их показателей у мужчин (18–26 лет) двух групп при легкой (14,5 % О2, n1=30) и средней (12,3 % О2, n2=29) ОНГ в течение 20 мин. Материал обработан с помощью программного пакета Statistica 10.0. Определяли нормальность распределения, применяли факторный анализ, корреляцию, регрессию. Результаты. При всех степенях ОНГ ведущий фактор включал QT, T1II и (с одним исключением) RR. При легкой ОНГ 1-й фактор на 5-й мин воздействия дополняется P1II, а при средней ОНГ на 20-й мин – P1II. Второй по весомости фактор при легкой ОНГ на 5-й и 20-й мин определяется BAR и RII, на 10-й мин – BAR, а при средней ОНГ на 5-й мин – P1II, на 10-й мин – RII и BAR, на 20-й мин – BAL. Показано, что при легкой ОНГ от исходных данных достоверно зависят отклонения P1II, RII, BAR и RR, при средней ОНГ такая зависимость наблюдается для RR и QT на 5-й и 10-й мин, для RII на 10-й и 20-й мин и для P1II на 20-й мин. Выводы. Основными маркерами биоэлектрических процессов сердца при ОНГ являются QT, T1II и RR, остальные параметры отличаются вариабельностью. Возможность прогноза отклонений параметров ЭКГ по их исходным величинам зависит от степени ОНГ. Ключевые слова: человек, гипоксия, оксигемометрия, электрокардиография, факторный, корреляционный, регрессионный анализы.

Acupuncture Effects on Cerebral Blood Flow during Normoxia and Normobaric Hypoxia: Results from a Prospective Crossover Pilot Study

Cerebral blood flow (CBF) is significantly influenced by exposure to hypoxia, both hypobaric and normobaric. Alterations in cerebral blood flow can play a crucial role in the pathogenesis of acute mountain sickness (AMS) and its symptoms, especially headache, dizziness, and nausea. Acupuncture has been proven to be effective in treating some cerebrovascular disorders and PC6 Nei Guan stimulation seems to enhance cerebral blood flow. Therefore, we have hypothesized that PC6 Nei Guan stimulation could affect CBF in acute hypoxia and could be used to contrast AMS symptoms. We evaluated blood flow in the middle cerebral artery (MCA) in normoxia, after 15 min in normobaric hypoxia (fraction of inspired oxygen (FiO2) 14%, corresponding to 3600 m a.s.l.) in basal conditions, and after PC6 Nei Guan stimulation, both by needle and by pressure. No comparisons with other acupuncture points and sham acupuncture were done. PC6 stimulation seemed to counteract the effects of acute normobaric hypoxia on end-diastolic velocity (EDV) in MCA, especially after acupuncture, and significantly reduced systolic and diastolic blood pressure. A rebalance of CBF could control some AMS symptoms, but further studies are necessary.

Intermittent normobaric hypoxia as a method of correction and prevention of functional changes in old age

The study involved men aged 60-65 years. The course of intermittent normobaric hypoxia (APG) was carried out for 3 weeks with breathing hypoxic gas mixture with 18-15-13-10% O2. Before and after the course, the reactivity of the cardiovascular system and blood system, physical performance were evaluated. It has been established that the course of APG increases oxidative metabolism, leads to a decrease in the level of sugar, total lipids and low-density lipids in the blood, an increase in the number of red blood cells, helps to reduce and stabilize blood pressure, increase physical performance of the elderly. The results of the study indicate the possibility of using APG as a method of correction and prevention of functional changes in the elderly. Key words: hypoxia, old age, blood, physical performance.

Temporary cardiointerval organization with varying degrees of acute normobaric hypoxia in a healthy person

The influence of acute normobaric hypoxia (ANH) on the male heart chronotropic effects was studied. Thus, a mild degree of ANH (14.5 % O2, 20 min), causing a decrease in blood oxygenation by 6.3 abs. %, accompanied by an initial (by 5 min) decrease in the RR and QT intervals. The average degree of ANH (12.3% O2) leads to a decrease in blood oxygenation by 19.7 abs. %. At the same time, in inverse relationship to the developing hypoxemia, RR and QT significantly decrease. Corrected values (Pc, PQc, QRSc, QTc) increase during the action period of an average degree of hypoxia, indicating an increase in the proportion of atrial contraction time, atrioventricular conduction of excitation and electrical ventricular systole in the total RR duration, which, apparently, provides optimal systolic heart effect. Key words: human, hypoxia, blood oxygenation, cardiointervals.

Self-Selected Motivational Music Enhances Physical Performance in Normoxia and Hypoxia in Young Healthy Males

Humans exposed to hypoxia are susceptible to physiological and psychological impairment. Music has ergogenic effects through enhancing psychological factors such as mood, emotion, and cognition. This study aimed to investigate music as a tool for mitigating the performance decrements observed in hypoxia. Thirteen males (mean ± SD; 24 ± 4 years) completed one familiarization session and four experimental trials; (1) normoxia (sea level, 0.209 FiO2) and no music; (2) normoxia (0.209 FiO2) with music; (3) normobaric hypoxia (∼3800 m, 0.13 FiO2) and no music; and (4) normobaric hypoxia (0.13 FiO2) with music. Experimental trials were completed at 21°C with 50% relative humidity. Music was self-selected prior to the familiarization session. Each experimental trial included a 15-min time trial on an arm bike, followed by a 60-s isometric maximal voluntary contraction (MVC) of the biceps brachii. Supramaximal nerve stimulation quantified central and peripheral fatigue with voluntary activation (VA%) calculated using the doublet interpolation method. Average power output (W) was reduced with a main effect of hypoxia (p = 0.02) and significantly increased with a main effect of music (p = 0.001). When combined the interaction was additive (p = 0.87). Average MVC force (N) was reduced in hypoxia (p = 0.03) but VA% of the biceps brachii was increased with music (p = 0.02). Music reduced subjective scores of mental effort, breathing discomfort, and arm discomfort in hypoxia (p < 0.001). Music increased maximal physical exertion through enhancing neural drive and diminishing detrimental mental processes, enhancing performance in normoxia (6.3%) and hypoxia (6.4%).