Ventilation during simulated altitude, normobaric hypoxia and normoxic hypobaria

Loeppky, Jack A.; Icenogle, Milton V.; Scotto, P.; Robergs, Robert A.; Hinghofer‐Szalkay, Helmut; Roach, Robert C.

doi:10.1016/s0034-5687(97)02523-1

Cited by 84 publications

(108 citation statements)

References 3 publications

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“…Loeppky et al, 1997;Savourey et al, 2003), it could be argued that the present results might not be representative of those expected in a hypobaric hypoxic setting. However, a previous study has shown that the hand CIVD responses are similar in normobaric and hypobaric hypoxia (Meeuwsen et al, 2009).…”

Section: Methodological Considerationscontrasting

confidence: 71%

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Keramidas

Kölegård

Mekjavic

et al. 2014

High Altitude Medicine & Biology

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Keramidas, Michail E, Roger Kölegård, Igor B. Mekjavic, and Ola Eiken. Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress. High Alt Med Biol. 15:183-191, 2014.-The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8°C water, during which they were inspiring either room air (Fio 2 : 0.21; AIR), or a hypoxic gas mixture (Fio 2 : 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 -0.5°C, HYPO: 10.0 -0.5°C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 -3.4°C; HYPO: 22.0 -3.8°C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.

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Section: Methodological Considerationscontrasting

confidence: 71%

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Keramidas

Kölegård

Mekjavic

et al. 2014

High Altitude Medicine & Biology

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“…This significant increase in ventilation at 3, 6 and 9 hours will not affect this study because the 20 km time trial will take highly trained athletes less than an hour to complete. The subjects will have a similar ventilatory response to hypobaric hypoxia while they exercise in normobaric hypoxia (23).…”

Section: Work Of Breathing In Hypoxiamentioning

confidence: 99%

Inspiratory Muscle Training and Endurance Performance in Hypoxia

Hursh

Wiggins

Bielko

et al. 2017

Medicine &Amp; Science in Sports &Amp; Exercise

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Ventilation is higher at any submaximal workload in hypoxia as compared to normoxia. Whether or not training the respiratory muscles helps to improve exercise performance in hypoxia is unclear. Purpose: To determine if improvements in ventilatory strength with chronic inspiratory muscle training (IMT) improves 20km cycling time trial (TT) performance in hypoxia (FIO2 = 16.1%). Methods: Thirteen highly-trained men were pair-matched based on pre-exercise values of maximal inspiratory pressure (MIP) and randomly placed into either a sham (n = 5, V O2max = 61.7 ± 2.0 ml•kg -1 •min -1 ) or an IMT (n = 8, V O2max = 63.5 ± 3.4 ml•kg TT heart rate and SpO2 were unchanged in both groups post-training. Conclusion: In a small cohort, IMT-induced improvements in respiratory muscle strength which resulted in greater ventilation and oxygen uptake during a 20km time trial in hypoxia. IMT should be explored as a useful strategy for improving the quality of cycle exercise training and/or endurance exercise performance at altitude. Chapter I: IntroductionAthletes competing in a hypoxic environment experience a worsening of exercise performance. One of the main causes is a decline in arterial oxygenation which causes a decline in maximal oxygen consumption. The body compensates for the decline in arterial oxygenation by increasing ventilation, which increases work of breathing. During exercise in normoxia, it is estimated that the inspiratory muscles consume 10 to 15 percent of total body oxygen uptake (1).However, in hypoxia, the oxygen demand of the respiratory muscles increases an additional 20 to 30 percent (2). In response to an increase in work of breathing, the inspiratory muscles increase their oxygen supply by shunting blood away from the working muscle and to the inspiratory muscles (15). Therefore, this causes a decrease in locomotor muscle power production and increases the rate of fatigue.There have been many different theories and techniques used to attenuate the effects of altitude on exercise performance. Inspiratory muscle training (IMT) has been shown to increase performance during a cycling time trial of 20 km or longer in a normoxic environment (20, 34). 7Interestingly, to our knowledge, there has only been one study examining the effects of IMT on performance in hypoxia. In this study by Downey et al., IMT increased oxygen diffusing capacity and arterial oxygen saturation while decreasing ventilation, cardiac output and inspiratory muscle fatigue during a treadmill time to exhaustion test (TTE) in hypoxia (8). Based on these results one would expect exercise performance in hypoxia to benefit from IMT, but there was no significant difference in the time to exhaustion test on a treadmill between the IMT and sham training groups. A lack of significant difference in exercise performance in hypoxia in the Downey et al. study may be due to the specific performance trial used not being robust enough to detect differences. The duration, for the experimental and control group, was 9.7 ± 1.5 min and 7.4 ± 1.2 m...

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“…O incremento da altitude, ao estar associado ao decréscimo exponencial da pressão barométrica e, paralelamente, da pressão parcial de oxigénio no ar atmosférico (PIO 2 ), promove alterações no conteúdo arterial de oxigénio e, em consequência, na "quantidade" de oxigénio fornecido aos tecidos (45,47). Conforme Torricelli referia em 1643 (84), vivemos submersos num oceano de ar que, mediante experiências inquestionáveis, sabemos ter peso, por isso, tomando como referência a pressão barométrica ao nível do mar (760 mmHg), à medida que subimos em altitude a pressão exercida por esta camada de ar, isto é, a pressão barométrica, vai diminuindo.…”

Section: A Hipóxia Hipobáricaunclassified

“…Um dos mecanismos de adaptação fisiológica mais característicos, inerente à exposição aguda a elevadas altitudes, é o incremento acentuado da frequência respiratória e do volume corrente (27,45,72,84). Esta resposta ventilatória à hipóxia induzida, essencialmente, pela estimulação de químio-receptores periféricos (11,43) sensíveis às variações do conteú-do arterial de oxigénio, possibilita o incremento da Fisiologia de altitude ventilação de 2 a 5 vezes relativamente aos valores obtidos ao nível do mar e, com isso, o aumento da pressão alveolar parcial de oxigénio alveolar (38,73).…”

Section: Adaptações Ventilatóriasunclassified

O desafio da altitude. Uma perspectiva fisiológica

Magalhães¹,

Duarte²,

Ascensão³

et al. 2002

RPCD

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RESUMOA prática de actividades físicas em altitude tem sofrido um aumento significativo ao longo dos últimos anos. Estas actividades, de que são exemplo o montanhismo, o alpinismo e o esqui, implicam a exposição esporádica ou prolongada dos "turistas de altitude" a ambientes de hipóxia hipobárica e, em consequência, induzem elevada agressão orgânica. No presente trabalho serão descritas as adaptações fisiológicas agudas e cró-nicas que ocorrem (i) nos sistemas respiratório e circulatório, (ii) nos componentes hematológicos e (iii) na morfologia e metabolismo musculares, com o objectivo de atenuar os efeitos fisiológicos da rarefação do oxigénio no ar atmosférico, possibilitando a permanência e a funcionalidade do Homem nestes locais hostis. Na perspectiva do rendimento desportivo, serão abordados, de forma sumária, o efeito fisiológico e os benefí-cios para o desempenho ao nível do mar decorrentes do denominado "treino em altitude". Palavras-chave:Altitude, hipóxia, adaptações fisiológicas agudas, adaptações fisiológicas crónicas, treino em altitude. ABSTRACT

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Ventilation during simulated altitude, normobaric hypoxia and normoxic hypobaria

Cited by 84 publications

References 3 publications

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Acute Effects of Normobaric Hypoxia on Hand-Temperature Responses During and After Local Cold Stress

Inspiratory Muscle Training and Endurance Performance in Hypoxia

O desafio da altitude. Uma perspectiva fisiológica

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