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Normobaric hypoxia

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https://www.readbyqxmd.com/read/27864638/effects-of-caffeine-on-neuromuscular-fatigue-and-performance-during-high-intensity-cycling%C3%A2-exercise-in-moderate-hypoxia
#1
Bruno P C Smirmaul, Antonio Carlos de Moraes, Luca Angius, Samuele M Marcora
PURPOSE: To investigate the effects of caffeine on performance, neuromuscular fatigue and perception of effort during high-intensity cycling exercise in moderate hypoxia. METHODS: Seven adult male participants firstly underwent an incremental exercise test on a cycle ergometer in conditions of acute normobaric hypoxia (fraction inspired oxygen = 0.15) to establish peak power output (PPO). In the following two visits, they performed a time to exhaustion test (78 ± 3% PPO) in the same hypoxic conditions after caffeine ingestion (4 mg kg(-1)) and one after placebo ingestion in a double-blind, randomized, counterbalanced cross-over design...
November 18, 2016: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/27856711/pulmonary-vascular-collagen-content-not-cross-linking-contributes-to-right-ventricular-pulsatile-afterload-and-overload-in-early-pulmonary-hypertension
#2
Zhijie Wang, David A Schreier, Hinnah Abid, Timothy A Hacker, Naomi C Chesler
Hypoxic pulmonary hypertension (HPH) is associated with pulmonary artery (PA) remodeling and right ventricular (RV) overload. We have previously uncovered collagen-mediated mechanisms of proximal PA stiffening in early HPH by manipulating collagen degradation and crosslinking using a transgenic mouse strain and a potent collagen cross-link inhibitor β-aminopropionitrile (BAPN). However, the roles of collagen in distal PA remodeling, overall RV afterload and RV hypertrophy in HPH remain unknown. Here, we used the same experimental strategy to investigate the impact of pulmonary vascular collagen content and cross-linking on steady and pulsatile RV afterload as well as RV hypertrophy in early HPH...
November 17, 2016: Journal of Applied Physiology
https://www.readbyqxmd.com/read/27847819/acute-mountain-sickness-symptoms-depend-on-normobaric-versus-hypobaric-hypoxia
#3
Dana M DiPasquale, Gary E Strangman, N Stuart Harris, Stephen R Muza
Acute mountain sickness (AMS), characterized by headache, nausea, fatigue, and dizziness when unacclimatized individuals rapidly ascend to high altitude, is exacerbated by exercise and can be disabling. Although AMS is observed in both normobaric (NH) and hypobaric hypoxia (HH), recent evidence suggests that NH and HH produce different physiological responses. We evaluated whether AMS symptoms were different in NH and HH during the initial stages of exposure and if the assessment tool mattered. Seventy-two 8 h exposures to normobaric normoxia (NN), NH, or HH were experienced by 36 subjects...
2016: BioMed Research International
https://www.readbyqxmd.com/read/27800505/fifteen-days-of-3-200-m-simulated-hypoxia-marginally-regulates-markers-for-protein-synthesis-and-degradation-in-human-skeletal-muscle
#4
Gommaar D'Hulst, Alessandra Ferri, Damien Naslain, Luc Bertrand, Sandrine Horman, Marc Francaux, David J Bishop, Louise Deldicque
Chronic hypoxia leads to muscle atrophy. The molecular mechanisms responsible for this phenomenon are not well defined in vivo. We sought to determine how chronic hypoxia regulates molecular markers of protein synthesis and degradation in human skeletal muscle and whether these regulations were related to the regulation of the hypoxia-inducible factor (HIF) pathway. Eight young male subjects lived in a normobaric hypoxic hotel (FiO2 14.1%, 3,200 m) for 15 days in well-controlled conditions for nutrition and physical activity...
2016: Hypoxia
https://www.readbyqxmd.com/read/27765844/intermittent-hypobaric-hypoxia-combined-with-aerobic-exercise-improves-muscle-morphofunctional-recovery-after-eccentric-exercise-to-exhaustion-in-trained-rats
#5
David Rizo-Roca, Juan Gabriel Ríos-Kristjánsson, Cristian Núñez-Espinosa, Estela Santos-Alves, Ines O Goncalves, Jose Magalhaes, Antonio A Ascensao, Teresa Pagès, Ginés Viscor, Joan Ramon Torrella
Unaccustomed eccentric exercise leads to muscle morphological and functional alterations, including microvasculature damage, the repair of which is modulated by hypoxia. Here we present the effects of intermittent hypobaric hypoxia and exercise on recovery from eccentric-induced muscle damage (EEIMD). Soleus muscles from trained rats were excised pre- (CTRL) and 1, 3, 7 and 14 days after a double session of EEIMD protocol. A recovery treatment consisting of one of the following protocols was applied one day after the EEIMD: passive normobaric recovery (PNR), a 4-hour daily exposure to passive hypobaric hypoxia at 4000m (PHR) or hypobaric hypoxia exposure followed by aerobic exercise (AHR)...
October 20, 2016: Journal of Applied Physiology
https://www.readbyqxmd.com/read/27765746/heart-lung-interaction-in-a-model-of-copd-importance-of-lung-volume-and-direct-ventricular-interaction
#6
William S Cheyne, Alexandra M Williams, Megan I Harper, Neil D Eves
Chronic obstructive pulmonary disease (COPD) is associated with dynamic lung hyperinflation (DH), increased pulmonary vascular resistance (PVR), and large increases in negative intrathoracic pressure (nITP). The individual and interactive effect of these stressors on left ventricular (LV) filling, emptying, and geometry and the role of direct ventricular interaction (DVI) in mediating these interactions have not been fully elucidated. Twenty healthy subjects were exposed to the following stressors alone and in combination: 1) inspiratory resistive loading of -20 cmH2O (nITP), 2) expiratory resistive loading to cause dynamic hyperinflation (DH), and 3) normobaric-hypoxia to increase PVR (hPVR)...
December 1, 2016: American Journal of Physiology. Heart and Circulatory Physiology
https://www.readbyqxmd.com/read/27750391/clarification-on-altitude-training
#7
Grégoire P Millet, Franck Brocherie, Raphael Faiss, Olivier Girard
The authors report that many LHTL studies in normobaric hypoxia (NH) "failed to show a positive outcome", which in our view is only partially true. In a cross-over design, we (Saugy et al. 2016) recently tested if LHTL in hypobaric hypoxia (HH) would lead to larger performance enhancement than in NH. Our hypothesis was that HH (i.e. natural altitude) would lead to larger enhancement than NH but the results were contrary to this hypothesis. So we cannot support the affirmation by Lundby & Robach that "natural altitude remains the best approach"...
October 17, 2016: Experimental Physiology
https://www.readbyqxmd.com/read/27744292/walking-economy-at-simulated-high-altitude-in-human-healthy-young-male-lowlanders
#8
Masahiro Horiuchi, Yoko Handa, Daijiro Abe, Yoshiyuki Fukuoka
We measured oxygen consumption during walking per unit distance (Cw) values for 12 human healthy young males at six speeds from 0.667 to 1.639 m s(-1) (four min per stage) on a level gradient under normobaric normoxia, moderate hypoxia (15% O2), and severe hypoxia (11% O2). Muscle deoxygenation (HHb) was measured at the vastus lateralis muscle using near-infrared spectroscopy. Economical speed which can minimize the Cw in each individual was calculated from a U-shaped relationship. We found a significantly slower economical speed (ES) under severe hypoxia [1...
October 15, 2016: Biology Open
https://www.readbyqxmd.com/read/27721912/effect-of-high-intensity-training-in-normobaric-hypoxia-on-thoroughbred-skeletal-muscle
#9
Hiroshi Nagahisa, Kazutaka Mukai, Hajime Ohmura, Toshiyuki Takahashi, Hirofumi Miyata
Hypoxic training is believed to increase endurance capacity in association with hypoxia inducible factor-1α (HIF-1α), a modulator of vascular endothelial growth factor-A (VEGF-A), and to influence activation of satellite cells (SCs). However, the effect of hypoxic training on SC activation and its relation to angiogenesis has not been thoroughly investigated. Eight Thoroughbred horses were subjected to normoxic (FIO2 = 21%) or hypoxic (FIO2 = 15%) training for 3 days/week (100%  [Formula: see text]) for 4 weeks...
2016: Oxidative Medicine and Cellular Longevity
https://www.readbyqxmd.com/read/27708611/a-history-of-mild-traumatic-brain-injury-affects-peripheral-pulse-oximetry-during-normobaric-hypoxia
#10
Leonard A Temme, Paul St Onge, Joseph Bleiberg
INTRODUCTION: Physiological and emotional stressors increase symptoms of concussion in recently injured individuals and both forms of stress-induced symptoms in people recovering from mild traumatic brain injury (mTBI), but who are asymptomatic when not stressed or are at rest. METHODS: Healthy asymptomatic adults (25.0 ± 5.1 years) with a history of mTBI (n = 36) and matched healthy controls (HC) (n = 36) with no mTBI history were exposed to three levels of normobaric hypoxic stress generated with the Reduced Oxygen Breathing Device (ROBD) (Environics, Inc...
2016: Frontiers in Neurology
https://www.readbyqxmd.com/read/27694473/simvastatin-prevents-and-reverses-chronic-pulmonary-hypertension-in-newborn-rats-via-pleiotropic-inhibition-of-rhoa-signaling
#11
Mathew J Wong, Crystal Kantores, Julijana Ivanovska, Amish Jain, Robert P Jankov
Chronic neonatal pulmonary hypertension (PHT) frequently results in early death. Systemically administered Rho-kinase (ROCK) inhibitors prevent and reverse chronic PHT in neonatal rats, but at the cost of severe adverse effects, including systemic hypotension and growth restriction. Simvastatin has pleiotropic inhibitory effects on isoprenoid intermediates that may limit activity of RhoA, which signals upstream of ROCK. We therefore hypothesized that statin treatment would safely limit pulmonary vascular RhoA activity and prevent and reverse experimental chronic neonatal PHT via downstream inhibitory effects on pathological ROCK activity...
September 30, 2016: American Journal of Physiology. Lung Cellular and Molecular Physiology
https://www.readbyqxmd.com/read/27689470/normobaric-hypoxia-effects-on-balance-measured-by-computerized-dynamic-posturography
#12
Dale R Wagner, Skyler Saunders, Brady Robertson, John E Davis
: Wagner, Dale R., Skyler Saunders, Brady Robertson, and John E. Davis. Normobaric hypoxia effects on balance measured by computerized dynamic posturography. High Alt Med Biol. 17:222-227, 2016.-Background/Aim: Equilibrium was measured by computerized dynamic posturography at varying levels of normobaric hypoxia before and after exercise. METHODS: Following a familiarization trial, 12 males (27.3 ± 7.1 years) completed three sessions in random order on a NeuroCom SMART Balance Master: a sham trial at the ambient altitude of 1500 m and simulated altitudes of 3000 and 5000 m created by a hypoxic generator...
September 2016: High Altitude Medicine & Biology
https://www.readbyqxmd.com/read/27672589/a-novel-model-of-retinopathy-of-prematurity-in-normobaric-hyperoxic-conditions
#13
Taner Ozgurtas, Sercan Tekin, Fatih Yesildal, Umut Karaca, Fevzi Nuri Aydin, Muhammed Talha Ugurlu, Mehmet Ozler, Hakan Durukan
AIM: To examine changes in retinal vasculature after treatment with different oxygen concentrations from common retinopathy of prematurity (ROP) models and to determine a novel and practical ROP model. METHODS: A sample of 14 newborn Sprague-Dawley rats was used. The study group (n=7) was exposed to 95% oxygen for 4h per day followed by normoxic laboratory conditions for 20h. This cycle was repeated for 14d. The control group (n=7) was subjected to normobaric normoxic conditions...
2016: International Journal of Ophthalmology
https://www.readbyqxmd.com/read/27642493/protection-of-pentoxifylline-against-testis-injury-induced-by-intermittent-hypobaric-hypoxia
#14
Chen Yao, Gang Li, Yeyong Qian, Ming Cai, Hong Yin, Li Xiao, Wei Tang, Fengjie Guo, Bingyi Shi
To investigate the effect of pentoxifylline (PTX) on spermatogenesis dysfunction induced by intermittent hypobaric hypoxia (IHH) and unveil the underlying mechanism, experimental animals were assigned to Control, IHH+Vehicle, and IHH+PTX groups and exposed to 4 cycles of 96 h of hypobaric hypoxia followed by 96 h of normobaric normoxia for 32 days. PTX was administered for 32 days. Blood and tissue samples were collected 7 days thereafter. Serum malondialdehyde levels were used to assess lipid peroxidation; ferric-reducing antioxidant power (FRAP), superoxide dismutase, and catalase and glutathione peroxidase enzyme activities were assessed to determine antioxidant capacity in various samples...
2016: Oxidative Medicine and Cellular Longevity
https://www.readbyqxmd.com/read/27553127/dietary-nitrate-supplementation-enhances-high-intensity-running-performance-in-moderate-normobaric-hypoxia-independent-of-aerobic-fitness
#15
Oliver Michael Shannon, Lauren Duckworth, Matthew John Barlow, David Woods, Jose Lara, Mario Siervo, John Paul O'Hara
Nitrate-rich beetroot juice (BRJ) increases plasma nitrite concentrations, lowers the oxygen cost (V⋅O2) of steady-state exercise and improves exercise performance in sedentary and moderately-trained, but rarely in well-trained individuals exercising at sea-level. BRJ supplementation may be more effective in a hypoxic environment, where the reduction of nitrite into nitric oxide (NO) is potentiated, such that well-trained and less well-trained individuals may derive a similar ergogenic effect. We conducted a randomised, counterbalanced, double-blind placebo controlled trial to determine the effects of BRJ on treadmill running performance in moderate normobaric hypoxia (equivalent to 2500 m altitude) in participants with a range of aerobic fitness levels...
September 30, 2016: Nitric Oxide: Biology and Chemistry
https://www.readbyqxmd.com/read/27536249/similar-inflammatory-responses-following-sprint-interval-training-performed-in-hypoxia-and-normoxia
#16
Alan J Richardson, Rebecca L Relf, Arron Saunders, Oliver R Gibson
Sprint interval training (SIT) is an efficient intervention capable of improving aerobic capacity and exercise performance. This experiment aimed to determine differences in training adaptations and the inflammatory responses following 2 weeks of SIT (30 s maximal work, 4 min recovery; 4-7 repetitions) performed in normoxia or hypoxia. Forty-two untrained participants [(mean ± SD), age 21 ±1 years, body mass 72.1 ±11.4 kg, and height 173 ±10 cm] were equally and randomly assigned to one of three groups; control (CONT; no training, n = 14), normoxic (NORM; SIT in FiO2: 0...
2016: Frontiers in Physiology
https://www.readbyqxmd.com/read/27506309/unexpected-reductions-in-regional-cerebral-perfusion-during-prolonged-hypoxia
#17
Justin S Lawley, Jamie H Macdonald, Samuel J Oliver, Paul G Mullins
Hypoxia causes an increase in global cerebral blood flow, which maintains global cerebral oxygen delivery and metabolism. Yet neurological deficits are abundant under hypoxic conditions. We investigated regional cerebral microvascular responses to acute (2 h) and prolonged (10 h) poikilocapnic normobaric hypoxia. We found that 2 h of hypoxia caused an expected increase in frontal cortical grey matter perfusion, but unexpected perfusion decreases in regions of the brain normally associated with the "default mode" or "task negative" network...
August 9, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/27460635/alterations-in-autonomic-cardiac-modulation-in-response-to-normobaric-hypoxia
#18
David Giles, John Kelly, Nick Draper
PURPOSE: The present study aimed to determine if autonomic cardiac modulation was influenced by acute exposure to normobaric hypoxia. METHOD: Ten healthy male lowland dwellers completed five block-randomised single-blinded, crossed-over acute exposures to a normobaric hypoxic environment, each separated by 24 hours' recovery (20.3%, 17.4%, 14.5%, 12.0% and 9.8% FIO2). Supine recordings were made of arterial oxygen saturation and electrocardiogram (ECG). RR intervals from the ECG trace were analysed for time (SDNN, lnrMSSD), frequency (lnVLF, lnLF, lnHF, lnTP, LFnu, and HFnu), and nonlinear (DFA-α1 and SampEn) heart rate variability components...
November 2016: European Journal of Sport Science
https://www.readbyqxmd.com/read/27443510/on-the-combined-effects-of-normobaric-hypoxia-and-bed-rest-upon-bone-and-mineral-metabolism-results-from-the-planhab-study
#19
Jörn Rittweger, Tadej Debevec, Petra Frings-Meuthen, Patrick Lau, Uwe Mittag, Bergita Ganse, Philip G Ferstl, Elizabeth J Simpson, Ian A Macdonald, Ola Eiken, Igor B Mekjavic
Bone losses are common as a consequence of unloading and also in patients with chronic obstructive pulmonary disease (COPD). Although hypoxia has been implicated as an important factor to drive bone loss, its interaction with unloading remains unresolved. The objective therefore was to assess whether human bone loss caused by unloading could be aggravated by chronic hypoxia. In a cross-over designed study, 14 healthy young men underwent 21-day interventions of bed rest in normoxia (NBR), bed rest in hypoxia (HBR), and hypoxic ambulatory confinement (HAmb)...
October 2016: Bone
https://www.readbyqxmd.com/read/27435029/effect-of-progressive-normobaric-hypoxia-on-dynamic-cerebral-autoregulation
#20
Masahiro Horiuchi, Junko Endo, Shohei Dobashi, Masataka Kiuchi, Katsuhiro Koyama, Andrew W Subudhi
What is the central question of this study? Acute hypoxia reduces dynamic cerebral autoregulation (dCA); however, it is unclear what level of hypoxia is necessary to exert this effect. We sought to investigate whether dCA would be reduced during progressive periods of normobaric hypoxia using a duplex Doppler ultrasound technique to evaluate the volumetric blood flow. What is the main finding and its importance? We showed that dCA decreased linearly as inspired O2 decreased from 21 to 12%. Additionally, symptoms of acute mountain sickness were related to changes in dCA...
October 1, 2016: Experimental Physiology
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