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Hypoxic Training Is Not Beneficial in Elite Athletes
... Although altitude training theoretically increases endurance performance, scientific evidence is controversial. 2,12,13 In addition, research on normobaric LHTLH is limited, even though it is implemented by athletes. Thus, the aim of this study is to investigate whether 4 weeks of normobaric LHTLH during a preparation season causes different hematological, cardiorespiratory, and sea-level performance changes in national and international level XC skiers compared to the skiers who live and train in normoxia. ...
... There was a significant main effect for time on body mass (F = 64.4, p < 0.001) but no time × group interaction (F = 2.5, p = 0. 13) showing that body mass decreased regardless of the group. ...
... Despite several studies having reported the effectiveness of LHTL on endurance performance, results remain controversial. 2,13 Our findings are in line with previous research that suggests that LHTL does not increase exercise performance and should not be recommended for endurance athletes. 12,13,23,24 Nevertheless, other literature describes the performance benefits of LHTL. 2 For example, Hauser et al. 25 found that 3 km running performance increased more in male triathletes F I G U R E 2 Changes in maximal oxygen uptake (VO 2max ) (A) and time to exhaustion (TTE) (B) during 4-week period either in normobaric hypoxia (LHTLH) or in normoxia (CON). ...
Purpose
To investigate whether 4 weeks of normobaric “live high–train low and high” (LHTLH) causes different hematological, cardiorespiratory, and sea‐level performance changes compared to living and training in normoxia during a preparation season.
Methods
Nineteen (13 women, 6 men) cross‐country skiers competing at the national or international level completed a 28‐day period (∼18 h day⁻¹) of LHTLH in normobaric hypoxia of ∼2400 m (LHTLH group) including two 1 h low‐intensity training sessions per week in normobaric hypoxia of 2500 m while continuing their normal training program in normoxia. Hemoglobin mass (Hbmass) was assessed using a carbon monoxide rebreathing method. Time to exhaustion (TTE) and maximal oxygen uptake (VO2max) were measured using an incremental treadmill test. Measurements were completed at baseline and within 3 days after LHTLH. The control group skiers (CON) (seven women, eight men) performed the same tests while living and training in normoxia with ∼4 weeks between the tests.
Results
Hbmass in LHTLH increased 4.2 ± 1.7% from 772 ± 213 g (11.7 ± 1.4 g kg⁻¹) to 805 ± 226 g (12.5 ± 1.6 g kg⁻¹) (p < 0.001) while it was unchanged in CON (p = 0.21). TTE improved during the study regardless of the group (3.3 ± 3.4% in LHTLH; 4.3 ± 4.8% in CON, p < 0.001). VO2max did not increase in LHTLH (61.2 ± 8.7 mL kg⁻¹ min⁻¹ vs. 62.1 ± 7.6 mL kg⁻¹ min⁻¹, p = 0.36) while a significant increase was detected in CON (61.3 ± 8.0–64.0 ± 8.1 mL kg⁻¹ min⁻¹, p < 0.001).
Conclusions
Four‐week normobaric LHTLH was beneficial for increasing Hbmass but did not support the short‐term development of maximal endurance performance and VO2max when compared to the athletes who lived and trained in normoxia.
... Endurance training sessions under hypoxic conditions are part of altitude training concepts for competitive athletes [1], as well as in preventive and therapeutic settings [2,3]. The positive effects of hypoxia application on sport performance and health outcomes have been extensively described in literature, but there are also negative reports [4,5] that should not be ignored, especially since negative health effects (e.g., an increased mechanic stress against the cerebral vessel wall) are also suspected [5]. The determination of exercise intensity zones plays a key role in regulating training adaptations and preventing under or over strain. ...
... Endurance training sessions under hypoxic conditions are part of altitude training concepts for competitive athletes [1], as well as in preventive and therapeutic settings [2,3]. The positive effects of hypoxia application on sport performance and health outcomes have been extensively described in literature, but there are also negative reports [4,5] that should not be ignored, especially since negative health effects (e.g., an increased mechanic stress against the cerebral vessel wall) are also suspected [5]. The determination of exercise intensity zones plays a key role in regulating training adaptations and preventing under or over strain. ...
The present project compared acute hypoxia-induced changes in lactate thresholds (methods according to Mader, Dickhuth and Cheng) with changes in high-intensity endurance performance. Six healthy and well-trained volunteers conducted graded cycle ergometer tests in normoxia and in acute normobaric hypoxia (simulated altitude 3000 m) to determine power output at three lactate thresholds (PMader, PDickhuth, PCheng). Subsequently, participants performed two maximal 30-min cycling time trials in normoxia (test 1 for habituation) and one in normobaric hypoxia to determine mean power output (Pmean). PMader, PDickhuth and PCheng decreased significantly from normoxia to hypoxia by 18.9 ± 9.6%, 18.4 ± 7.3%, and 11.5 ± 6.0%, whereas Pmean decreased by only 8.3 ± 1.6%. Correlation analyses revealed strong and significant correlations between Pmean and PMader (r = 0.935), PDickhuth (r = 0.931) and PCheng (r = 0.977) in normoxia and partly weaker significant correlations between Pmean and PMader (r = 0.941), PDickhuth (r = 0.869) and PCheng (r = 0.887) in hypoxia. PMader and PCheng did not significantly differ from Pmean (p = 0.867 and p = 0.784) in normoxia, whereas this was only the case for PCheng (p = 0.284) in hypoxia. Although investigated in a small and select sample, the results suggest a cautious application of lactate thresholds for exercise intensity prescription in hypoxia.
... Although AT has been extensively applied and is trusted by coaches and athletes (Daniels and Oldridge, 1970;Solli et al., 2017), its effectiveness on aerobic performance remains unclear (Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020). In general, the ambiguity originates from two aspects: 1) Potential negative effects of chronic hypoxia exposure (various types of acute altitude sickness) (Imray et al., 2010;Schommer et al., 2012), which outweighs potential benefits and 2) unreasonable hypoxic doses . ...
Objective: This study aimed to compare and rank the effect of hypoxic practices on maximum oxygen consumption (VO 2 max) in athletes and determine the hypoxic dose-response correlation using network meta-analysis.
Methods: The Web of Science, PubMed, EMBASE, and EBSCO databases were systematically search for randomized controlled trials on the effect of hypoxc interventions on the VO 2 max of athletes published from inception until 21 February 2023. Studies that used live-high train-high (LHTH), live-high train-low (LHTL), live-high, train-high/low (HHL), intermittent hypoxic training (IHT), and intermittent hypoxic exposure (IHE) interventions were primarily included. LHTL was further defined according to the type of hypoxic environment (natural and simulated) and the altitude of the training site (low altitude and sea level). A meta-analysis was conducted to determine the standardized mean difference between the effects of various hypoxic interventions on VO 2 max and dose-response correlation. Furthermore, the hypoxic dosage of the different interventions were coordinated using the “kilometer hour” model.
Results: From 2,072 originally identified titles, 59 studies were finally included in this study. After data pooling, LHTL, LHTH, and IHT outperformed normoxic training in improving the VO 2 max of athletes. According to the P-scores, LHTL combined with low altitude training was the most effective intervention for improving VO 2 max (natural: 0.92 and simulated: 0.86) and was better than LHTL combined with sea level training (0.56). A reasonable hypoxic dose range for LHTH (470–1,130 kmh) and HL (500–1,415 kmh) was reported with an inverted U-shaped curve relationship.
Conclusion: Different types of hypoxic training compared with normoxic training serve as significant approaches for improving aerobic capacity in athletes. Regardless of the type of hypoxic training and the residential condition, LHTL with low altitude training was the most effective intervention. The characteristics of the dose-effect correlation of LHTH and LHTL may be associated with the negative effects of chronic hypoxia.
... Despite the activation of HIFs by exercise and although exercise in hypoxic conditions has become an important training modality, as preparation for competitions in high altitude [186], to increase general athletic performance (although this remains debated [187,188]) or as a potential alternative to heavy training for load-compromised individuals [189], the interplay of mitochondria and HIFs during exercise is not well understood yet. ...
Reduced oxygen availability (hypoxia) can lead to cell and organ damage. Therefore, aerobic species depend on efficient mechanisms to counteract detrimental consequences of hypoxia. Hypoxia inducible factors (HIFs) and mitochondria are integral components of the cellular response to hypoxia and coordinate both distinct and highly intertwined adaptations. This leads to reduced dependence on oxygen, improved oxygen supply, maintained energy provision by metabolic remodeling and tapping into alternative pathways and increased resilience to hypoxic injuries. On one hand, many pathologies are associated with hypoxia and hypoxia can drive disease progression, for example in many cancer and neurological diseases. But on the other hand, controlled induction of hypoxia responses via HIFs and mitochondria can elicit profound health benefits and increase resilience. To tackle pathological hypoxia conditions or to apply health-promoting hypoxia exposures efficiently, cellular and systemic responses to hypoxia need to be well understood. Here we first summarize the well-established link between HIFs and mitochondria in orchestrating hypoxia-induced adaptations and then outline major environmental and behavioral modulators of their interaction that remain poorly understood.
... Altitude hypoxia training has become a popular means to increase endurance athletes' performance for decades (18)(19)(20)(21)(22). What's more, current research indicates that chronic intermittent hypoxic-hyperoxic periods exposure at rest is beneficial for older patients with cardiovascular and metabolic diseases or cognitive impairment to improve physical and cognitive performance and reduce cardiometabolic risk factors (23). Despite much research in this area to date, the results are highly controversial as intraindividual and interindividual variabilities (24,25). More studies are needed to confirm and extend the evidence. ...
Introduction
Musculoskeletal system gradually degenerates with aging, and a hypoxia environment at a high altitude may accelerate this process. However, the comprehensive effects of high-altitude environments on bones and muscles remain unclear. This study aims to compare the differences in bones and muscles at different altitudes, and to explore the mechanism and influencing factors of the high-altitude environment on the skeletal muscle system.
Methods
This is a prospective, multicenter, cohort study, which will recruit a total of 4000 participants over 50 years from 12 research centers with different altitudes (50m~3500m). The study will consist of a baseline assessment and a 5-year follow-up. Participants will undergo assessments of demographic information, anthropomorphic measures, self-reported questionnaires, handgrip muscle strength assessment (HGS), short physical performance battery (SPPB), blood sample analysis, and imaging assessments (QCT and/or DXA, US) within a time frame of 3 days after inclusion. A 5-year follow-up will be conducted to evaluate the changes in muscle size, density, and fat infiltration in different muscles; the muscle function impairment; the decrease in BMD; and the osteoporotic fracture incidence. Statistical analyses will be used to compare the research results between different altitudes. Multiple linear, logistic regression and classification tree analyses will be conducted to calculate the effects of various factors (e.g., altitude, age, and physical activity) on the skeletal muscle system in a high-altitude environment. Finally, a provisional cut-off point for the diagnosis of sarcopenia in adults at different altitudes will be calculated.
Ethics and dissemination
The study has been approved by the institutional research ethics committee of each study center (main center number: KHLL2021-KY056). Results will be disseminated through scientific conferences and peer-reviewed publications, as well as meetings with stakeholders.
Clinical Trial registration number
http://www.chictr.org.cn/index.aspx , identifier ChiCTR2100052153.
... The benefits of altitude training for endurance athletes are still debated in the scientific literature 4,5 ; however, it is a common practice, particularly in professional cycling, 6 with many cyclists undergoing altitude camps (eg, Sierra Nevada, Spain; Teide Volcano, Spain; Tignes, France; Boyacá, Colombia) to prepare for the Grand Tours (ie, Giro d'Italia, Tour de France, and Vuelta Espana) that involve alternating between different hypoxic methods, such as live high-train high or live high-train low, to develop aerobic capacity as a result of increased hemoglobin mass. 7,8 Beyond the well-known variability in responses to hypoxia among athletes, 9 the altitude level of birth and childhood appear as key factors: In a recent study of 33 male professional cyclists, altitude levels influenced anaerobic (30-s and 1-min mean maximal power above 1500 m) and aerobic (5-min; 10-min above 2000 m) performances differently between lowlanders and altitude natives, which might confer a competitive advantage for highlanders at altitudes >1500 m. 6 The highlander professional cyclists come from different locations worldwide (eg, The United States, Ecuador, Colombia, Eritrea), but the Colombian cyclists are the most numerous and have had the best performances during the last decade; that is, several Colombian cyclists have been on the podium in the most important races, including the Vuelta Espana, Giro d'Italia, and Tour de France. ...
Objective: To determine whether the altitude of birth/childhood influences the values in peak power output (PPO) and estimated maximum oxygen uptake (estVO2max) in male Colombian road cyclists of different performance levels. This study also aimed to determine whether cyclists born at high altitudes tend to be more successful. Methods: Eighty riders aged between 17 and 22 years of 3 performance levels (U23 world-class level, WC, n = 8; U23 national level, N23, n = 41; junior national level, J, n = 31) and 3 altitude levels (<800 m, low; 800–2000 m, moderate; >2000 m, high) performed an
ergocycle maximal incremental test to exhaustion at an altitude of 2570 m. Results: Altogether, while cyclists born at an altitude >2000 m represented ∼50% of the analyzed sample, there was a significantly higher proportion (84%) of these cyclists who had participated as professionals in a Grand Tour (χ2[1, N = 80] = 4.58, P < .05). Riders of the low group had lower values of PPO and estVO2max than cyclists of moderate and high altitudes, while no differences were noted between moderate- and high-altitude groups. In N23, PPO and estVO2max were lower in the low- than in the moderate-altitude group, while in the J cyclists, PPO and estVO2max were lower in the low-altitude compared with both moderate- and high-altitude groups. Discussion: Among the cyclists tested at altitude in junior and U23, there is an overrepresentation of individuals who reached an elite level and were born at a high altitude (>2000 m). As no clear differences were observed between moderate- and high-altitude cyclists, the higher prevalence of elite cyclists in the latter group may originate from various—still unclear—mechanisms.
... Despite this accumulating body of scientific evidence to the efficacy of LHTH, conflicting opinion still exists. It is possible that large individual variability, poorly designed studies and inconclusive evidence, alongside proposed counteractive maladaptive responses [70], have resulted in the notion that altitude training might not work for all athletes [44]. This argument is valid since not all individuals respond to hypoxia in the same way, but more likely on a hypoxic sensitivity continuum, which in turn determines the physiological response to hypoxia, and subsequent aerobic performance at altitude [53]. ...
PurposeElite endurance runners frequently utilise live high-train high (LHTH) altitude training to improve endurance performance at sea level (SL). Individual variability in response to the hypoxic exposure have resulted in contradictory findings. In the present case study, changes in total haemoglobin mass (tHbmass) and physiological capacity, in response to 4-weeks of LHTH were documented. We tested if a hypoxic sensitivity test (HST) could predict altitude-induced adaptations to LHTH.Methods
Fifteen elite athletes were selected to complete 4-weeks of LHTH (~ 2400 m). Athletes visited the laboratory for preliminary testing (PRE), to determine lactate threshold (LT), lactate turn point (LTP), maximal oxygen uptake VO2max and tHbmass. During LHTH, athletes completed daily physiological measures [arterial oxygen saturation (SpO2) and body mass] and subjective wellbeing questions. Testing was repeated, for those who completed the full camp, post-LHTH (POST). Additionally, athletes completed the HST prior to LHTH.ResultsA difference (P < 0.05) was found from PRE to POST in average tHbmass (1.8% ± 3.4%), VO2max (2.7% ± 3.4%), LT (6.1% ± 4.6%) and LTP (5.4% ± 3.8%), after 4-weeks LHTH. HST revealed a decrease in oxygen saturation at rest (ΔSpr) and higher hypoxic ventilatory response at rest (HVRr) predicted individual changes tHbmass. Lower hypoxic cardiac response at rest (HCRr) and higher HVRr predicted individual changes VO2max.Conclusion
Four weeks of LHTH at ~ 2400 m increased tHbmass and enhanced physiological capacity in elite endurance runners. There was no observed relationship between these changes and baseline characteristics, pre-LHTH serum ferritin levels, or reported incidents of musculoskeletal injury or illness. The HST did however, estimate changes in tHbmass and VO2max. HST prior to LHTH could allow coaches and practitioners to better inform the acclimatisation strategies and training load application of endurance runners at altitude.
... repeated sprint training in hypoxia) [33][34][35][36] or a combination of hypoxic methods [1,37] seems a promising approach for performance enhancement in moderately to well-trained populations and elite athletes. Nevertheless, it has also been stated that the use of hypoxic training methods (whether at rest or in combination with exercise) has been strongly promoted in elite athletes for many years without any evidence for their justification, which is still under debate [36,38]. Studies conducted with healthy non-athletic populations have shown that IH at rest or in combination with physical exercises can be a valuable strategy to improve cognitive functions (e.g. ...
Background
Intermittent hypoxia applied at rest or in combination with exercise promotes multiple beneficial adaptations with regard to performance and health in humans. It was hypothesized that replacing normoxia by moderate hyperoxia can increase the adaptive response to the intermittent hypoxic stimulus.
Objective
Our objective was to systematically review the current state of the literature on the effects of chronic intermittent hypoxia–hyperoxia (IHH) on performance- and health-related outcomes in humans.
Methods
PubMed, Web of Science™, Scopus, and Cochrane Library databases were searched in accordance with PRISMA guidelines (January 2000 to September 2021) using the following inclusion criteria: (1) original research articles involving humans, (2) investigation of the chronic effect of IHH, (3) inclusion of a control group being not exposed to IHH, and (4) articles published in peer-reviewed journals written in English.
Results
Of 1085 articles initially found, eight studies were included. IHH was solely performed at rest in different populations including geriatric patients ( n = 1), older patients with cardiovascular ( n = 3) and metabolic disease ( n = 2) or cognitive impairment ( n = 1), and young athletes with overtraining syndrome ( n = 1). The included studies confirmed the beneficial effects of chronic exposure to IHH, showing improvements in exercise tolerance, peak oxygen uptake, and global cognitive functions, as well as lowered blood glucose levels. A trend was discernible that chronic exposure to IHH can trigger a reduction in systolic and diastolic blood pressure. The evidence of whether IHH exerts beneficial effects on blood lipid levels and haematological parameters is currently inconclusive. A meta-analysis was not possible because the reviewed studies had a considerable heterogeneity concerning the investigated populations and outcome parameters.
Conclusion
Based on the published literature, it can be suggested that chronic exposure to IHH might be a promising non-pharmacological intervention strategy for improving peak oxygen consumption, exercise tolerance, and cognitive performance as well as reducing blood glucose levels, and systolic and diastolic blood pressure in older patients with cardiovascular and metabolic diseases or cognitive impairment. However, further randomized controlled trials with adequate sample sizes are needed to confirm and extend the evidence. This systematic review was registered on the international prospective register of systematic reviews (PROSPERO-ID: CRD42021281248) ( https://www.crd.york.ac.uk/prospero/ ).
... Altitude training is typically included in the annual training plan as 2-4-week camps at low to moderate altitudes (i.e., ∼ 1,400-2,500 m) (Millet et al., 2010;Mujika et al., 2019). While there are conflicting views on the effects of altitude training on subsequent sea-level performance (Lundby and Robach, 2016;Millet et al., 2019;Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020), there is consensus that acclimatization to altitude is necessary for optimal performance at altitude Burtscher et al., 2018a). Current recommendations suggest that ∼ 14 days of acclimatization at the same altitude as the competition is sufficient at moderate to high altitudes (i.e., 2,000-4,500 m) (Bärtsch et al., 2008;Bergeron et al., 2012;Chapman et al., 2013;Burtscher et al., 2018a). ...
Objective: To monitor the daily variations and time course of changes in selected variables during a 17–21-day altitude training camp at 1,800 m in a group of elite cross-country skiers (9 women, 12 men) and biathletes (7 women, 4 men).
Methods: Among other variables, resting peripheral oxygen saturation (SpO2rest), resting heart rate (HRrest) and urine specific gravity (USG) were monitored daily at altitude, while illness symptoms were monitored weekly. Before and after the camp, body composition (i.e., lean and fat mass) and body mass were assessed in all athletes, while roller-skiing speed at a blood lactate concentration of 4 mmol·L−1 (Speed@4mmol) was assessed in the biathletes only.
Results: Neither SpO2rest, HRrest nor USG changed systematically during the camp (p > 0.05), although some daily time points differed from day one for the latter two variables (p < 0.05). In addition, body composition and body mass were unchanged from before to after the camp (p > 0.05). Eleven out of 15 illness episodes were reported within 4 days of the outbound or homebound flight. The five biathletes who remained free of illness increased their Speed@4mmol by ~ 4% from before to after the camp (p = 0.031).
Conclusions: The present results show that measures typically recommended to monitor acclimatization and responses to altitude in athletes (e.g., SpO2rest and HRrest) did not change systematically over time. Further research is needed to explore the utility of these and other measures in elite endurance athletes at altitudes typical of competition environments
... This clini cal review focuses on the aim of improving sealevel performance through hypoxic training at natural or simulated moderate altitude in highly trained and elite endurance athletes. There is a considerable and growing body of scientific literature on this topic, but the evidence is by no means conclusive [e.g., (19,34)]. Here, we aim to summarize the existing knowledge of altitude training for increasing sealevel perfor mance, to highlight the ambiguities, and to outline guiding principles within the narrow corridors of evidence. ...
Many endurance athletes aim to increase endurance performance at or near sea-level by hypoxic training, which can be realized in natural or artificial altitude via three main concepts: living and training in hypoxia, living in hypoxia and training in normoxia, or living in normoxia and training in hypoxia. The scientific evidence for these concepts is surprisingly unclear, although several ergogenic adaptations to hypoxic training are well described. Hematologic acclimatization through an increase in hemoglobin mass is often considered the most important factor. But hematologic acclimatization does not explain the performance increase found by some studies, indicating other mechanisms and confounders determine successful training adaptation. This clinical review briefly summarizes the current, conflicting knowledge, lists confounders potentially influencing the outcome, and provides some practical guidance to coaches and clinicians for monitoring and optimizing hypoxic training as far as covered by evidence.
... It has been questioned whether altitude training has positive effects on endurance capacity and sea-level performance beyond the effects achieved with similar training performed at sea level. Here, high-quality scientific evidence is limited, and researchers interpret the current scientific data differently [195,196]. Altitude training research is methodologically demanding due to the difficulty of standardizing the intervention, including control groups, and controlling other psychological and physiological confounders during altitude training. Although research provides limited support for a positive effect of altitude training on sea-level performance in endurance sports, these studies remain scarce and underpowered to detect the small adaptations that may be of importance in elite LDR. ...
In this review we integrate the scientific literature and results-proven practice and outline a novel framework for understanding the training and development of elite long-distance performance. Herein, we describe how fundamental training characteristics and well-known training principles are applied. World-leading track runners (i.e., 5000 and 10,000 m) and marathon specialists participate in 9 ± 3 and 6 ± 2 (mean ± SD) annual competitions, respectively. The weekly running distance in the mid-preparation period is in the range 160–220 km for marathoners and 130–190 km for track runners. These differences are mainly explained by more running kilometers on each session for marathon runners. Both groups perform 11–14 sessions per week, and ≥ 80% of the total running volume is performed at low intensity throughout the training year. The training intensity distribution vary across mesocycles and differ between marathon and track runners, but common for both groups is that volume of race-pace running increases as the main competition approaches. The tapering process starts 7–10 days prior to the main competition. While the African runners live and train at high altitude (2000–2500 m above sea level) most of the year, most lowland athletes apply relatively long altitude camps during the preparation period. Overall, this review offers unique insights into the training characteristics of world-class distance runners by integrating scientific literature and results-proven practice, providing a point of departure for future studies related to the training and development in the Olympic long-distance events.
... Moderate altitude training has emerged as a popular method to improve athletic endurance performance (Girard et al., 2013a;Millet and Brocherie, 2020). However, the underlying mechanisms have not been fully clarified (Girard et al., 2013a;Zhao et al., 2018;Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020). Recent evidence indicated that exercise and the gut microbiota were interconnected (Przewłócka et al., 2020;Clauss et al., 2021). ...
Hypoxia environment has been widely used to promote exercise capacity. However, the underlying mechanisms still need to be further elucidated. In this study, mice were exposed to the normoxia environment (21% O 2 ) or hypoxia environment (16.4% O 2 ) for 4 weeks. Hypoxia-induced gut microbiota remodeling characterized by the increased abundance of Akkermansia and Bacteroidetes genera, and their related short-chain fatty acids (SCFAs) production. It was observed that hypoxia markedly improved endurance by significantly prolonging the exhaustive running time, promoting mitochondrial biogenesis, and ameliorating exercise fatigue biochemical parameters, including urea nitrogen, creatine kinase, and lactic acid, which were correlated with the concentrations of SCFAs. Additionally, the antibiotics experiment partially inhibited hypoxia-induced mitochondrial synthesis. The microbiota transplantation experiment demonstrated that the enhancement of endurance capacity induced by hypoxia was transferable, indicating that the beneficial effects of hypoxia on exercise performance were partly dependent on the gut microbiota. We further identified that acetate and butyrate, but not propionate, stimulated mitochondrial biogenesis and promoted endurance performance. Our results suggested that hypoxia exposure promoted endurance capacity partially by the increased production of SCFAs derived from gut microbiota remodeling.
... Altitude training is a common strategy employed by elite endurance athletes to induce physiological adaptations, with a potential to improve subsequent performance at altitude and/or sea level. [1][2][3] Thus, elite endurance athletes commonly integrate training camps at low-to-moderate altitudes (eg, » 1400-2500 m) lasting 2À4 weeks into their annual training periodization. 2 The most extensively studied adaptive response linked to altitude training is the erythropoietin-driven increases in red blood cell volume and total hemoglobin mass. 2 Although there are conflicting views, 3,4 these hematological changes are considered to represent the main mechanism for improved endurance performance at sea level following periods of altitude training. 2 Optimization of altitude adaptations depends on various factors, such as the hypoxic dose, training load and recovery, oxygen saturation (SpO 2 ), iron and energy availability and illness status. ...
Objectives:
To observe changes in sleep from baseline and during an altitude training camp in elite endurance athletes.
Design:
Prospective, observational.
Setting:
Baseline monitoring at <500 m for 2 weeks and altitude monitoring at 1800 m for 17-22 days.
Participants:
Thirty-three senior national-team endurance athletes (mean age 25.8 ± S.D. 2.8 years, 16 women).
Measurements:
Daily measurements of sleep (using a microwave Doppler radar at baseline and altitude), oxygen saturation (SpO2), training load and subjective recovery (at altitude).
Results:
At altitude vs. baseline, sleep duration (P = .036) and light sleep (P < .001) decreased, while deep sleep (P < .001) and respiration rate (P = .020) increased. During the first altitude week vs. baseline, deep sleep increased (P = .001). During the first vs. the second and third altitude weeks, time in bed (P = .005), sleep duration (P = .001), and light sleep (P < .001) decreased. Generally, increased SpO2 was associated with increased deep sleep while increased training load was associated with increased respiration rate.
Conclusion:
This is the first study to document changes in sleep from near-sea-level baseline and during a training camp at 1800 m in elite endurance athletes. Ascending to altitude reduced total sleep time and light sleep, while deep sleep and respiration rate increased. SpO2 and training load at altitude were associated with these responses. This research informs our understanding of the changes in sleep occurring in elite endurance athletes attending training camps at competition altitudes.
... High-intensity or (repeated-)sprint exercise may induce local tissue hypoxia (with reduced PO 2 ) leading to stabilization of the transcription factor HIF-1α, which increases transcription of genes for capillary growth (Lundby et al., 2009;Egan and Zierath, 2013). Although controversies may exist (e.g., Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020), when performed in hypoxia, high-intensity training also seems effective in increasing transcription of VEGF and Mb (Vogt et al., 2001;Kanatous et al., 2009;Faiss et al., 2013;Brocherie et al., 2018). Importantly, the prolonged low-intensity exercise in polarized training could stimulate muscle protein breakdown via enhanced expression of E3 ligases (Stefanetti et al., 2015), resulting in small muscle fibers that facilitate oxygen diffusion to the mitochondria. ...
In the past decades, researchers have extensively studied (elite) athletes' physiological responses to understand how to maximize their endurance performance. In endurance sports, whole-body measurements such as the maximal oxygen consumption, lactate threshold, and efficiency/economy play a key role in performance. Although these determinants are known to interact, it has also been demonstrated that athletes rarely excel in all three. The leading question is how athletes reach exceptional values in one or all of these determinants to optimize their endurance performance, and how such performance can be explained by (combinations of) underlying physiological determinants. In this review, we advance on Joyner and Coyle's conceptual framework of endurance performance, by integrating a meta-analysis of the interrelationships, and corresponding effect sizes between endurance performance and its key physiological determinants at the macroscopic (whole-body) and the microscopic level (muscle tissue, i.e., muscle fiber oxidative capacity, oxygen supply, muscle fiber size, and fiber type). Moreover, we discuss how these physiological determinants can be improved by training and what potential physiological challenges endurance athletes may face when trying to maximize their performance. This review highlights that integrative assessment of skeletal muscle determinants points toward efficient type-I fibers with a high mitochondrial oxidative capacity and strongly encourages well-adjusted capillarization and myoglobin concentrations to accommodate the required oxygen flux during endurance performance, especially in large muscle fibers. Optimisation of endurance performance requires careful design of training interventions that fine tune modulation of exercise intensity, frequency and duration, and particularly periodisation with respect to the skeletal muscle determinants.
... This training is usually distributed over 2-4 relatively short periods (e.g., ~ 14-18 days) each year, with training at 1500-3000 m, while living at ~ 1800-2000 m [55,63,70]. At the same time, the extent to which altitude training may enhance performance at sea level is widely debated [41,60]. However, the current commentary will primarily discuss training at altitude for optimal acclimatization and performance during competitions at low-to-moderate altitudes (e.g. ...
At the 2022 Winter Olympics in Beijing, the XC skiing, biathlon and nordic combined events will be held at altitudes of ~ 1700 m above sea level, possibly in cold environmental conditions and while requiring adjustment to several time zones. However, the ongoing COVID-19 pandemic may lead to sub-optimal preparations. The current commentary provides the following evidence-based recommendations for the Olympic preparations: make sure to have extensive experience of training (> 60 days annually) and competition at or above the altitude of competition (~ 1700 m), to optimize and individualize your strategies for acclimatization and competition. In preparing for the Olympics, 10–14 days at ~ 1700 m seems to optimize performance at this altitude effectively. An alternative strategy involves two–three weeks of training at > 2000 m, followed by 7–10 days of tapering off at ~ 1700 m. During each of the last 3 or 4 days prior to departure, shift your sleeping and eating schedule by 0.5–1 h towards the time zone in Beijing. In addition, we recommend that you arrive in Beijing one day earlier for each hour change in time zone, followed by appropriate timing of exposure to daylight, meals, social contacts, and naps, in combination with a gradual increase in training load. Optimize your own individual procedures for warming-up, as well as for maintaining body temperature during the period between the warm-up and competition, effective treatment of asthma (if necessary) and pacing at ~ 1700 m with cold ambient temperatures. Although we hope that these recommendations will be helpful in preparing for the Beijing Olympics in 2022, there is a clear need for more solid evidence gained through new sophisticated experiments and observational studies.
... Recent innovative "live low-train high" methods are now well established for improving repeated-sprint ability in team-sport athletes, 1 but paradoxically the effectiveness of the "most traditional" altitude training methods ("live high-train high" LHTH or "live high-train low" LHTL) in endurance athletes remains a topic highly debated between scientists. 2,3 Among the many points to be further explored in these 2 methods, the mechanisms and time course of postaltitude adaptations (ie, when the athlete returns to sea level) remain under-investigated. [4][5][6] For this period, Chapman et al 6 proposed that the deacclimatization responses of hematological (eg, erythropoietin, plasma volume, hemoglobin mass), ventilatory (eg, ventilation, VO 2 max), and biomechanical/neuromuscular (eg, muscle recruitment, running mechanics) factors would interact to determine the time course of performance capacity in athletes. ...
Aims:
It has been hypothesized that altitude training may alter running mechanics due to several factors such as the slower training velocity with associated alteration in muscle activation and coordination. This would lead to an altered running mechanics attested by an increase in mechanical work for a given intensity and to the need to "re-establish" the neuromuscular coordination and running biomechanics postaltitude. Therefore, the present study aimed to test the hypothesis that "live high-train high" would induce alteration in the running biomechanics (ie, longer contact time, higher vertical oscillations, decreased stiffness, higher external work).
Methods:
Before and 2 to 3 days after 3 weeks of altitude training (1850-2200 m), 9 national-level middle-distance (800-5000 m) male runners performed 2 successive 5-minute bouts of running at moderate intensity on an instrumented treadmill with measured ground reaction forces and gas exchanges. Immediately after the running trials, peak knee extensor torque was assessed during isometric maximal voluntary contraction.
Results:
Except for a slight (-3.0%; P = .04) decrease in vertical stiffness, no mechanical parameters (stride frequency and length, contact and flight times, ground reaction forces, and kinetic and potential work) were modified from prealtitude to postaltitude camp. Running oxygen cost was also unchanged.
Discussion:
The present study is the first one to report that "live high-train high" did not change the main running mechanical parameters, even when measured immediately after the altitude camp. This result has an important practical implication: there is no need for a corrective period at sea level for "normalizing" the running mechanics after an altitude camp.
... In addition to obtaining hematological benefits of altitude acclimatization, one advantage of LHTL is the maintenance of training intensity and oxygen flux comparable to sea level (Levine and Stray-Gundersen 1997). However, despite the widespread use of altitude training among professional athletes, contrasting views exist in the literature regarding LHTL effects on sea-level performance (Millet and Brocherie 2020;Siebenmann and Dempsey, 2020). Because of the natural degradation of the hypoxic adaptations over time (Chapman et al. 2014b), a promising approach would be to include a LHTL training period after a natural altitude sojourn to retain LHTH-induced adaptations. ...
PurposeTo test the hypothesis that hypoxic re-exposure after return from natural altitude training is beneficial in retaining hematological and performance adaptations.Methods
Eighteen mixed martial art fighters completed a 3-weeks natural altitude training camp at 2418 m. Afterwards, participants were randomly assigned to a living high-training low (12 h/d at a simulated altitude of 2800 m) group (LHTL, n = 9) or a living low-training low group (LLTL, n = 9) for a 3-week sea-level training period. At baseline and after return to sea level, hematological [hemoglobin mass (Hbmass) on days 2, 6, 9, 12, 15 and 21] and performance (3000 m time trial and maximal oxygen uptake on days 4, 6, 9, 15 and 21) markers were assessed.ResultsMean Hbmass increased from baseline to day 2 (11.7 ± 0.9 vs. 12.4 ± 1.3 g/kg; + 6.6 ± 7.5%; P < 0.05). While Hbmass remained elevated above baseline in LHTL (P < 0.001), it returned near baseline levels from day 9 in LLTL. Irrespective of groups, mean V̇O2max was only elevated above baseline at day 2 (+ 4.5 ± 0.8%) and day 9 (+ 3.8 ± 8.0%) (both P < 0.05). Compared to baseline, 3000 m running time decreased at day 4 (– 3.1 ± 3.3%; P < 0.05) and day 15 (– 2.8 ± 2.3%; P < 0.05) only.Conclusions
Despite re-exposure to hypoxia allowing a recovery of the hypoxic stimulus to retain Hbmass gains from previous altitude sojourn, there is no performance advantage of this practice above sea level residence. Our results also give support to empirical observations describing alternance of periods of optimal and attenuated performance upon return to sea level.
... In view of these multifaceted negative consequences to endurance performance at high altitude in the athletic sojourner, it appears paradoxical that such large numbers of elite athletes utilize training regimens requiring hypoxic exposure with the intent of enhancing their Hb mass and performance at sea level (131). The efficacy of this practice has recently been questioned (172,184). ...
In the healthy, untrained young adult a case is made for a respiratory system- airways, pulmonary vasculature, lung parenchyma, respiratory muscles and neural ventilatory control system - which is near ideally designed to ensure a highly efficient, homeostatic response to exercise of varying intensities and durations. Our aim was then to consider circumstances in which the intra/extra-thoracic airways, pulmonary vasculature, respiratory muscles and/or blood:gas distribution are underbuilt or inadequately regulated relative to the demands imposed by the cardiovascular system. In these instances, the respiratory system presents a significant limitation to O 2 transport and contributes to the occurrence of locomotor muscle fatigue, inhibition of central locomotor output and exercise performance. Most prominent in these examples of an "underbuilt" respiratory system are highly trained endurance athletes, with additional influences of sex, aging, hypoxic environments and the highly inbred equine. We summarize by evaluating the relative influences of these respiratory system limitations on exercise performance, their impact on pathophysiology and provide recommendations for future investigation.
... Siebenmann and Dempsey (26) argued that "the available evidence does not justify recommending any of the existing hypoxic training methods (LHTH, LHTL, or LLTH)." Despite our high respect for their work, our opponents' points are often confused, due to the use of many references not directly related to the topic and erroneous statements. ...
We aimed to identify potential physiological and performance differences of trained cross-country skiers (V˙o2max=60±4 ml ∙ kg–1 ∙ min–1) following two, 3-week long altitude modalities: 1) training at moderate altitudes (600–1700 m) and living at 1500 m (LMTM;N=8); and 2) training at moderate altitudes (600–1700 m) and living at 1500 m with additional nocturnal normobaric hypoxic exposures (FiO2 =0.17;LHTM; N=8). All participants conducted the same training throughout the altitude training phase and underwent maximal roller ski trials and submaximal cyclo-ergometery before, during and one week after the training camps. No exercise performance or hematological differences were observed between the two modalities. The average roller ski velocities were increased one week after the training camps following both LMTM (p=0.03) and LHTM (p=0.04) with no difference between the two (p=0.68). During the submaximal test, LMTM increased the Tissue Oxygenation Index (11.5±6.5 to 1.0±8.5%; p=0.04), decreased the total hemoglobin concentration (15.1±6.5 to 1.7±12.9 a.u.;p=0.02), and increased blood pH (7.36±0.03 to 7.39±0.03;p=0.03). On the other hand, LHTM augmented minute ventilation (76±14 to 88±10 l·min−1;p=0.04) and systemic blood oxygen saturation by 2±1%; (p=0.02) with no such differences observed following the LMTM. Collectively, despite minor physiological differences observed between the two tested altitude training modalities both induced comparable exercise performance modulation.
Although scientific conclusions remain equivocal, there is evidence-based research, as well as anecdotal support, suggesting that altitude training can enhance performance among Olympic level athletes, particularly in endurance sport. This appears to be due primarily to hypoxia-induced increases in total hemoglobin mass and subsequent improvements in maximal oxygen uptake and other factors contributing to aerobic performance. Although less clear, it is possible that non-hematological adaptations may contribute secondarily to improvements in post-altitude performance. These physiological effects are most likely realized when the altitude exposure is of sufficient “hypoxic dose” to provide the necessary stimuli for performance-affecting changes to occur via hypoxia-inducible factor 1α (HIF-1α) and hypoxia-inducible factor 2α (HIF-2α) pathways and their downstream molecular signaling. Team USA has made a strong commitment over the past 20 years to utilizing altitude training for the enhancement of performance in elite athletes in preparation for the Olympic Games and World Championships. Team USA’s strongest medal-producing Olympic sports—USA Swimming and USA Track and Field—embraced altitude training several years ago, and they continue to be leaders within Team USA in the practical and successful application of altitude training. Whereas USA Swimming utilizes traditional “live high and train high” (LH + TH) altitude training, USA Track and Field tends more toward the use of the altitude training strategy whereby athletes live high (and potentially sleep higher, either naturally or via simulated altitude), while training high during moderate-intensity (< lactate threshold 2) training sessions, and train low during high-intensity (> lactate threshold 2) training sessions (LH + TH[LT]). Although USA Swimming and USA Track and Field have taken different approaches to altitude training, they have been equally successful at the Olympic Games and World Championships, both teams being ranked first in the world based on medals earned in these major international competitions. In addition to USA Swimming and USA Track and Field, several other Team USA sports have had consistently competitive performance results in conjunction with regular and systematic altitude training blocks. The purpose of this paper was to describe select altitude training strategies used by Team USA athletes, and the impact of those strategies on podium performance at major international competitions, specifically the Olympic Games and World Championships.
PurposeThis single-blind, repeated measures study evaluated adaptive and maladaptive responses to continuous and intermittent hypoxic patterns in young adults.Methods
Changes in haematological profile, stress and cardiac damage were measured in ten healthy young participants during three phases: (1) breathing normoxic air (baseline); (2) breathing normoxic air via a mask (Sham-controls); (3) breathing intermittent hypoxia (IH) via a mask, mean peripheral oxygen saturation (SpO2) of 85% ~ 70 min of hypoxia. After a 5-month washout period, participants repeated this three-phase protocol with phase, (4) consisting of continuous hypoxia (CH), mean SpO2 = 85%, ~ 70 min of hypoxia. Measures of the red blood cell count (RBCc), haemoglobin concentration ([Hb]), haematocrit (Hct), percentage of reticulocytes (% Retics), secretory immunoglobulin A (S-IgA), cortisol, cardiac troponin T (cTnT) and the erythropoietic stimulation index (calculated OFF-score) were compared across treatments.ResultsDespite identical hypoxic durations at the same fixed SpO2, no significant effects were observed in either CH or Sham-CH control, compared to baseline. While IH and Sham-IH controls demonstrated significant increases in: RBCc; [Hb]; Hct; and the erythropoietic stimulation index. Notably, the % Retics decreased significantly in response to IH (-31.9%) or Sham-IH control (-23.6%), highlighting the importance of including Sham-controls. No difference was observed in S-IgA, cortisol or cTnT.Conclusion
The IH but not CH pattern significantly increased key adaptive haematological responses, without maladaptive increases in S-IgA, cortisol or cTnT, indicating that the IH hypoxic pattern would be the best method to boost haematological profiles prior to ascent to altitude.
A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat, by examining the benefits of heat acclimation, cooling strategies and hyperhydration. Finally, contemporary controversies are summarized and future research directions provided.
This study examined the physiological, physical and technical responses to repeated-sprint training in normobaric hypoxia [RSH, inspired fraction of oxygen (FiO2) 14.5%] vs. normoxia (RSN, FiO2 20.9%). Within 12 days, eighteen well-trained tennis players (RSH, n = 9 vs. RSN, n = 9) completed five specific repeated-sprint sessions which consisted of four sets of 5 maximal shuttle-run sprints. Testing sessions included repeated-sprint ability and Test to Exhaustion Specific to Tennis (TEST). TEST’s maximal duration to exhaustion and time to attain the ‘onset of blood lactate accumulation’ at 4 mMol.L-1 (OBLA) improvements were significantly higher in RSH compared to RSN. Change in time to attain OBLA was concomitant with similar observation in time to the second ventilatory threshold. Significant interaction (P = 0.003) was found for ball accuracy with greater increase in RSH (+13.8 %, P = 0.013) vs. RSN (-4.6 %, P = 0.15). A correlation (r = 0.59, P < 0.001) was observed between change in ball accuracy and TEST’s time to exhaustion. Greater improvement in some tennis-specific physical and technical parameters was observed after only 5 sessions of RSH vs. RSN in well-trained tennis players.
Keywords: Sport-Specific fitness; Hypoxia; Repeated-sprint ability; V̇O2max; Ball accuracy; Tennis Performance.
Purpose:
To analyze if live high-train low (LHTL) effectiveness is improved when daily training is guided by heart rate variability (HRV).
Methods:
Twenty-four elite Nordic skiers took part in a 15-day LHTL study and were randomized into a HRV-guided training hypoxic group (H-HRV, n = 9, sleeping in normobaric hypoxia, FiO2 = 15.0%) and two predefined training groups sleeping either in hypoxia (H, n = 9, FiO2 = 15.0%) or normoxia (N, n = 6). HRV and training loads (TL) were recorded daily. Prior (Pre), one (Post-1), and 21 days (Post-21) following LHTL, athletes performed a 10-km roller-ski test, and a treadmill test for determination of [Formula: see text] was performed at Pre and Post-1.
Results:
Some HRV parameters measured in supine position were different between H-HRV and H: low and high (HF) frequency power in absolute (ms2) (16.0 ± 35.1 vs. 137.0 ± 54.9%, p = 0.05) and normalized units (- 3.8 ± 10.1 vs. 53.0 ± 19.5%, p = 0.02), HF(nu) (6.3 ± 6.8 vs. - 13.7 ± 8.0%, p = 0.03) as well as heart rate (3.7 ± 6.3 vs. 12.3 ± 4.1%, p = 0.008). At Post-1, [Formula: see text] was improved in H-HRV and H (3.8 ± 3.1%; p = 0.02 vs. 3.0 ± 4.4%; p = 0.08) but not in N (0.9 ± 5.1%; p = 0.7). Only H-HRV improved the roller-ski performance at Post-21 (- 2.7 ± 3.6%, p = 0.05).
Conclusion:
The daily individualization of TL reduced the decrease in autonomic nervous system parasympathetic activity commonly associated with LHTL. The improved performance and oxygen consumption in the two LHTL groups confirm the effectiveness of LHTL even in elite endurance athletes.
The aim was to investigate whether 6 weeks of normobaric “Live High-Train Low” (LHTL) using altitude tents affect highly trained athletes incremental peak power, 26-km time-trial cycling performance, 3-min all-out performance, and 30-s repeated sprint ability. In a double-blinded, placebo-controlled cross-over design, seven highly trained triathletes were exposed to 6 weeks of normobaric hypoxia (LHTL) and normoxia (placebo) for 8 h/day. LHTL exposure consisted of 2 weeks at 2500 m, 2 weeks at 3000 m, and 2 weeks at 3500 m. Power output during an incremental test, ~26-km time trial, 3-min all-out exercise, and 8 × 30 s of all-out sprint was evaluated before and after the intervention. Following at least 8 weeks of wash-out, the subjects crossed over and repeated the procedure. Incremental peak power output was similar after both interventions [LHTL: 375 ± 74 vs. 369 ± 70 W (pre-vs-post), placebo: 385 ± 60 vs. 364 ± 79 W (pre-vs-post)]. Likewise, mean power output was similar between treatments as well as before and after each intervention for time trial [LHTL: 257 ± 49 vs. 254 ± 54 W (pre-vs-post), placebo: 267 ± 57 vs. 267 ± 52 W (pre-vs-post)], and 3-min all-out [LHTL: 366 ± 68 vs. 369 ± 72 W (pre-vs-post), placebo: 365 ± 66 vs. 355 ± 71 W (pre-vs-post)]. Furthermore, peak- and mean power output during repeated sprint exercise was similar between groups at all time points (n = 5). In conclusion, 6 weeks of normobaric LHTL using altitude tents simulating altitudes of 2500–3500 m conducted in a double-blinded, placebo-controlled cross-over design do not affect power output during an incremental test, a ~26-km time-trial test, or 3-min all-out exercise in highly trained triathletes. Furthermore, 30 s of repeated sprint ability was unaltered.
Background
Repeated-sprint training in hypoxia (RSH) is a recent intervention regarding which numerous studies have reported effects on sea-level physical performance outcomes that are debated. No previous study has performed a meta-analysis of the effects of RSH. Objective
We systematically reviewed the literature and meta-analyzed the effects of RSH versus repeated-sprint training in normoxia (RSN) on key components of sea-level physical performance, i.e., best and mean (all sprint) performance during repeated-sprint exercise and aerobic capacity (i.e., maximal oxygen uptake [\(\dot{V}{\text{O}}_{2\hbox{max} }\)]). Methods
The PubMed/MEDLINE, SportDiscus®, ProQuest, and Web of Science online databases were searched for original articles—published up to July 2016—assessing changes in physical performance following RSH and RSN. The meta-analysis was conducted to determine the standardized mean difference (SMD) between the effects of RSH and RSN on sea-level performance outcomes. ResultsAfter systematic review, nine controlled studies were selected, including a total of 202 individuals (mean age 22.6 ± 6.1 years; 180 males). After data pooling, mean performance during repeated sprints (SMD = 0.46, 95% confidence interval [CI] −0.02 to 0.93; P = 0.05) was further enhanced with RSH when compared with RSN. Although non-significant, additional benefits were also observed for best repeated-sprint performance (SMD = 0.31, 95% CI −0.03 to 0.89; P = 0.30) and \(\dot{V}{\text{O}}_{2\hbox{max} }\) (SMD = 0.18, 95% CI −0.25 to 0.61; P = 0.41). Conclusion
Based on current scientific literature, RSH induces greater improvement for mean repeated-sprint performance during sea-level repeated sprinting than RSN. The additional benefit observed for best repeated-sprint performance and \(\dot{V}{\text{O}}_{2\hbox{max} }\) for RSH versus RSN was not significantly different.
Saugy, Jonas J., Laurent Schmitt, Sibylle Fallet, Raphael Faiss, Jean-Marc Vesin, Mattia Bertschi, Raphael Heinzer, and Gregoire P. Millet. Sleep disordered breathing during live high-train low in normobaric versus hypobaric hypoxia. High Alt Med Biol. 16:000-000, 2016.-The present study aimed to compare sleep disordered breathing during live high-train low (LHTL) altitude camp using normobaric hypoxia (NH) and hypobaric hypoxia (HH). Sixteen highly trained triathletes completed two 18-day LHTL camps in a crossover designed study. They trained at 1100-1200 m while they slept either in NH at a simulated altitude of 2250 m or in HH. Breathing frequency and oxygen saturation (SpO2) were recorded continuously during all nights and oxygen desaturation index (ODI 3%) calculated. Breathing frequency was lower for NH than HH during the camps (14.6 +/- 3.1 breath x min-1 vs. 17.2 +/- 3.4 breath x min-1, p < 0.001). SpO2 was lower for HH than NH (90.8 +/- 0.3 vs. 91.9 +/- 0.2, p < 0.001) and ODI 3% was higher for HH than NH (15.1 +/- 3.5 vs. 9.9 +/- 1.6, p < 0.001). Sleep in moderate HH is more altered than in NH during a LHTL camp.
Purpose : Repeated-sprint training in hypoxia (RSH) has been shown as an efficient method for improving repeated sprint ability (RSA) in team-sport players but has not been investigated in swimming. We assessed whether RSH with arterial desaturation induced by voluntary hypoventilation at low lung volume (VHL) could improve RSA to a greater extent than the same training performed under normal breathing (NB) conditions. Methods : 16 competitive swimmers completed six sessions of repeated sprints (two sets of 16×15 m with 30 s send-off) either with VHL (RSH-VHL, n=8) or with NB (RSN, n=8). Before (pre-) and after (post-) training, performance was evaluated through an RSA test (25m all-out sprints with 35 s send-off) until exhaustion. Results : From pre- to post-, the number of sprints was significantly increased in RSH-VHL (7.1 ± 2.1 vs 9.6 ± 2.5; p<0.01) but not in RSN (8.0 ± 3.1 vs 8.7 ± 3.7; p=0.38). Maximal blood lactate concentration ([La]max) was higher at post compared to pre- in RSH-VHL (11.5 ± 3.9 vs 7.9 ± 3.7 mmol.l-137 ; p=0.04) but was unchanged in RSN (10.2 ± 2.0 vs 9.0 ± 3.5 mmol.l-138 ; p=0.34). There was a strong correlation between the increases in the number of sprints and in [La]max in RSH-VHL only (R=0.93; p<0.01).
Conclusion : Repeated sprint training in hypoxia induced by voluntary hypoventilation at low lung volume improved repeated sprint ability in swimming, probably through enhanced anaerobic glycolysis. This innovative method allows inducing benefits normally associated with hypoxia during swim training in normoxia.
Introduction:
This controlled, nonrandomized, parallel-groups trial investigated the effects on performance, V˙O2 and hemoglobin mass (tHbmass) of four preparatory in-season training interventions: living and training at moderate altitude for 3 and 4 wk (Hi-Hi3, Hi-Hi), living high and training high and low (Hi-HiLo, 4 wk), and living and training at sea level (SL) (Lo-Lo, 4 wk).
Methods:
From 61 elite swimmers, 54 met all inclusion criteria and completed time trials over 50- and 400-m crawl (TT50, TT400), and 100 (sprinters) or 200 m (nonsprinters) at best stroke (TT100/TT200). Maximal oxygen uptake (V˙O2max) and HR were measured with an incremental 4 × 200 m test. Training load was estimated using cumulative training impulse method and session RPE. Initial measures (PRE) were repeated immediately (POST) and once weekly on return to SL (PostW1 to PostW4). tHbmass was measured in duplicate at PRE and once weekly during the camp with CO rebreathing. Effects were analyzed using mixed linear modeling.
Results:
TT100 or TT200 was worse or unchanged immediately at POST, but improved by approximately 3.5% regardless of living or training at SL or altitude after at least 1 wk of SL recovery. Hi-HiLo achieved greater improvement 2 (5.3%) and 4 wk (6.3%) after the camp. Hi-HiLo also improved more in TT400 and TT50 2 (4.2% and 5.2%, respectively) and 4 wk (4.7% and 5.5%) from return. This performance improvement was not linked linearly to changes in V˙O2max or tHbmass.
Conclusions:
A well-implemented 3- or 4-wk training camp may impair performance immediately but clearly improves performance even in elite swimmers after a period of SL recovery. Hi-HiLo for 4 wk improves performance in swimming above and beyond altitude and SL controls through complex mechanisms involving altitude living and SL training effects.
During acute altitude exposure tachycardia increases cardiac output (Q) thus preserving systemic O2 delivery. Within days of acclimatization, however, Q normalizes following an unexplained reduction in stroke volume (SV). To investigate whether the altitude-mediated reduction in plasma volume (PV) and hence central blood volume (CBV) is the underlying mechanism we increased/decreased CBV by means of passive whole body head-down (HDT) and head-up (HUT) tilting in seven lowlanders at sea level (SL) and after 25/26 days of residence at 3454 m. Prior to the experiment on day 26, PV was normalized by infusions of a PV expander. Cardiovascular responses to whole body tilting were monitored by pulse contour analysis. After 25/26 days at 3454 m PV and blood volume decreased by 9 ± 4% and 6 ± 2%, respectively (P < 0.001 for both). SV was reduced compared to SL for each HUT angle (P < 0.0005). However, the expected increase in SV from HUT to HDT persisted and ended in the same plateau as at SL, albeit this was shifted 18 ± 20° toward HDT (P = 0.019). PV expansion restored SV to SL during HUT and to an ∼8% higher level during HDT (P = 0.003). The parallel increase in SV from HUT to HDT at altitude and SL to a similar plateau demonstrates an unchanged dependence of SV on CBV, indicating that the reduced SV during HUT was related to an attenuated CBV for a given tilt angle. Restoration of SV by PV expansion rules out a significant contribution of other mechanisms, supporting that resting SV at altitude becomes reduced due to a hypovolemia.
Travel to mountain areas is popular. However, the effects of acute exposure to moderate altitude on the cardiovascular system and metabolism are largely unknown.
To investigate the effects of acute exposure to moderate altitude on vascular function, metabolism and systemic inflammation.
In 51 healthy male subjects with a mean (SD) age of 26.9 (9.3) years, oxygen saturation, blood pressure, heart rate, arterial stiffness, lipid profiles, low density lipoprotein (LDL) particle size, insulin resistance (HOMA-index), highly-sensitive C-reactive protein and pro-inflammatory cytokines were measured at 490 m (Zurich) and during two days at 2590 m, (Davos Jakobshorn, Switzerland) in randomized order. The largest differences in outcomes between the two altitudes are reported.
Mean (SD) oxygen saturation was significantly lower at 2590 m, 91.0 (2.0)%, compared to 490 m, 96.0 (1.0)%, p<0.001. Mean blood pressure (mean difference +4.8 mmHg, p<0.001) and heart rate (mean difference +3.3 bpm, p<0.001) were significantly higher at 2590 m, compared to 490 m, but this was not associated with increased arterial stiffness. At 2590 m, lipid profiles improved (median difference triglycerides -0.14 mmol/l, p = 0.012, HDL +0.08 mmol/l, p<0.001, total cholesterol/HDL-ratio -0.25, p = 0.001), LDL particle size increased (median difference +0.45 nm, p = 0.048) and hsCRP decreased (median difference -0.18 mg/l, p = 0.024) compared to 490 m. No significant change in pro-inflammatory cytokines or insulin resistance was observed upon ascent to 2590 m.
Short-term stay at moderate altitude is associated with increased blood pressure and heart rate likely due to augmented sympathetic activity. Exposure to moderate altitude improves the lipid profile and systemic inflammation, but seems to have no significant effect on glucose metabolism.
ClinicalTrials.gov NCT01130948.
The combination of living at altitude and training near sea level [live high-train low (LHTL)] may improve performance of endurance athletes. However, to date, no study can rule out a potential placebo effect as at least part of the explanation, especially for performance measures. With the use of a placebo-controlled, double-blinded design, we tested the hypothesis that LHTL-related improvements in endurance performance are mediated through physiological mechanisms and not through a placebo effect. Sixteen endurance cyclists trained for 8 wk at low altitude (<1,200 m). After a 2-wk lead-in period, athletes spent 16 h/day for the following 4 wk in rooms flushed with either normal air (placebo group, n = 6) or normobaric hypoxia, corresponding to an altitude of 3,000 m (LHTL group, n = 10). Physiological investigations were performed twice during the lead-in period, after 3 and 4 wk during the LHTL intervention, and again, 1 and 2 wk after the LHTL intervention. Questionnaires revealed that subjects were unaware of group classification. Weekly training effort was similar between groups. Hb mass, maximal oxygen uptake (VO(2)) in normoxia, and at a simulated altitude of 2,500 m and mean power output in a simulated, 26.15-km time trial remained unchanged in both groups throughout the study. Exercise economy (i.e., VO(2) measured at 200 W) did not change during the LHTL intervention and was never significantly different between groups. In conclusion, 4 wk of LHTL, using 16 h/day of normobaric hypoxia, did not improve endurance performance or any of the measured, associated physiological variables.
The “living high–training low” model (LHTL), i.e., training in normoxia but sleeping/living in hypoxia, is designed to improve the athletes performance. However, LHTL efficacy still remains controversial and also little is known about the duration of its potential benefit. This study tested whether LHTL enhances aerobic performance in athletes, and if any positive effect may last for up to 2 weeks after LHTL intervention. Eighteen swimmers trained for 13 days at 1,200 m while sleeping/living at 1,200 m in ambient air (control, n=9) or in hypoxic rooms (LHTL, n=9, 5 days at simulated altitude of 2,500 m followed by 8 days at simulated altitude of 3,000 m, 16 h day−1). Measures were done before 1–2 days (POST-1) and 2 weeks after intervention (POST-15). Aerobic performance was assessed from two swimming trials, exploring
\( \ifmmode\expandafter\dot\else\expandafter\.\fi{V}{\text{O}}_{{2\max }} \) and endurance performance (2,000-m time trial), respectively. Reticulocyte, serum EPO and soluble transferrin receptor responses were not altered by LHTL, whereas reticulocytes decreased in controls. In POST-1 (vs. before): red blood cell volume increased in LHTL only (+8.5%, P=0.03),
\( \ifmmode\expandafter\dot\else\expandafter\.\fi{V}{\text{O}}_{{2\max }} \) tended to increase more in LHTL (+8.1%, P=0.09) than in controls (+2.5%, P=0.21) without any difference between groups (P=0.42) and 2,000-m performance was unchanged with LHTL. In POST-15, both performance and hematological parameters were similar to initial levels. Our results indicate that LHTL may stimulate red cell production, without any concurrent amelioration of aerobic performance. The absence of any prolonged benefit after LHTL suggests that this LHTL model cannot be recommended for long-term purposes.
Purpose:
A statistical method called "magnitude-based inference" (MBI) has gained a following in the sports science literature, despite concerns voiced by statisticians. Its proponents have claimed that MBI exhibits superior type I and type II error rates compared with standard null hypothesis testing for most cases. I have performed a reanalysis to evaluate this claim.
Methods:
Using simulation code provided by MBI's proponents, I estimated type I and type II error rates for clinical and nonclinical MBI for a range of effect sizes, sample sizes, and smallest important effects. I plotted these results in a way that makes transparent the empirical behavior of MBI. I also reran the simulations after correcting mistakes in the definitions of type I and type II error provided by MBI's proponents. Finally, I confirmed the findings mathematically; and I provide general equations for calculating MBI's error rates without the need for simulation.
Results:
Contrary to what MBI's proponents have claimed, MBI does not exhibit "superior" type I and type II error rates to standard null hypothesis testing. As expected, there is a tradeoff between type I and type II error. At precisely the small-to-moderate sample sizes that MBI's proponents deem "optimal," MBI reduces the type II error rate at the cost of greatly inflating the type I error rate-to two to six times that of standard hypothesis testing.
Conclusions:
Magnitude-based inference exhibits worrisome empirical behavior. In contrast to standard null hypothesis testing, which has predictable type I error rates, the type I error rates for MBI vary widely depending on the sample size and choice of smallest important effect, and are often unacceptably high. Magnitude-based inference should not be used.
Live high – train low (LHTL) using hypobaric hypoxia was previously found to improve sea-level endurance performance in well-trained individuals, however confirmatory controlled data in athletes are lacking. Here we test the hypothesis that natural-altitude LHTL improves aerobic performance in cross-country skiers, in conjunction with expansion of total hemoglobin mass (Hbmass, carbon-monoxide rebreathing technique) promoted by accelerated erythropoiesis. Following duplicate baseline measurements at sea level over the course of two weeks, nineteen Norwegian cross-country skiers (three women, sixteen men, age 20±2 yr, maximal oxygen uptake (VO2max) 69±5 ml.min⁻¹.kg⁻¹) were assigned to 26 consecutive nights spent either at low (1035m, Control, n=8) or moderate altitude (2207m, daily exposure 16.7±0.5 hours, LHTL, n=11). All athletes trained together daily at a common location ranging from 550-1500m (21.2% of training time at 550m, 44.2% at 550-800m, 16.6% at 800-1100m, 18.0% at 1100-1500m). Three test sessions at sea level were performed over the first three weeks after intervention. Despite the demonstration of nocturnal hypoxemia at moderate altitude (pulse oximetry), LHTL had no specific effect on serum erythropoietin, reticulocytes, Hbmass, VO2max or 3000-m running performance. Also LHTL had no specific effect on i) running economy (VO2 assessed during steady-state submaximal exercise), ii) respiratory capacities or efficiency of the skeletal muscle (biopsy), and iii) diffusing capacity of the lung. The present study, showing similar physiological responses and performance improvements in the two groups following intervention, suggests that in young cross-country skiers, improvements in sea-level aerobic performance associated with LHTL may not be due to moderate altitude acclimatization.
The novel hypothesis that "Live High-Train Low" (LHTL) does not improve sport-specific exercise performance (e.g., time trial) is discussed. Indeed, many studies demonstrate improved performance after LHTL but unfortunately control groups are often lacking, leaving open the possibility of training camp effects. Importantly, when control groups, blinding procedures and strict scientific evaluation criteria are applied, LHTL has no detectable effect on performance.
Exercise is associated with unequivocal health benefits and results in many structural and functional changes of the myocardium that enhance performance and prevent heart failure. However, intense exercise also presents a significant hemodynamic challenge in which the right-sided heart chambers are exposed to a disproportionate increase in afterload and wall stress that can manifest as myocardial fatigue or even damage if intense exercise is sustained for prolonged periods. This review focuses on the physiological factors that result in a disproportionate load on the right ventricle during exercise and the long-term consequences. The changes in cardiac structure and function that define a athlete's heart' disproportionately affect the right-sided heart chambers and this can raise important diagnostic overlap with some cardiac pathologies, particularly some inherited cardiomyopathies. The interaction between exercise and arrhythmogenic right ventricular cardiomyopathy (ARVC) will be highlighted as an important example of how hemodynamic stressors can combine with deficiencies in cardiac structural elements to cause cardiac dysfunction predisposing to arrhythmias. The extent to which extreme exercise can cause adverse remodelling in the absence of a genetic predisposition remains controversial. In the athlete with profound changes in heart structure, it can be extremely challenging to determine whether common symptoms such as palpitations may be a marker of more sinister arrhythmias. This review discusses some of the techniques that have recently been proposed to identify pathology in these circumstances. Finally, we will discuss recent evidence defining the role of exercise restriction as a therapeutic intervention in individuals predisposed to arrhythmogenic cardiomyopathy. © Published on behalf of the European Society of Cardiology. All rights reserved.
Cerebral blood flow (CBF) is regulated to secure brain O2 delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O2 delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (PIO2 = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min(-1), mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced PETCO2, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO2 in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO2 in hypoxia, leading to a similar brain O2 delivery during the sprints regardless of PIO2. In conclusion, when a conflict exists between preserving brain O2 delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O2 delivery.
Purpose:
Few recent studies indicate that short-term repeated sprint training in hypoxia (RSH) improves repeated sprint (RS) performance compared with identical training under normoxic conditions (RSN) in endurance-trained subjects. Herein, we sought to determine the effects of RSH against RSN on RS performance under normoxic and moderate hypoxic conditions, using a randomized, double-blind and cross-over experimental design.
Methods:
Fifteen endurance-trained male subjects (age=25±4 years) performed 4 weeks of RS training (3 sessions/week) in normobaric hypoxia (RSH, FiO2=13.8 %) and normoxia (RSN, FiO2=20.9 %) in a cross-over manner. Prior to and after completion of training, RS tests were performed on a cycle ergometer (i) with no prior exercise (RSNE), (ii) after an incremental exercise test (RSIE) and (iii) after a time trial test (RSTT), in normoxia and hypoxia.
Results:
Peak power output at the incremental exercise test and time trial performance were unaltered by RSH in normoxia and hypoxia. RS performance was generally enhanced by RSH as well as RSN, but there were no additional effects of RSH over RSN on peak and mean sprint power output and the number of repeated sprints performed in the RSNE, RSIE and RSTT trials under normoxic and hypoxic conditions.
Conclusions:
The present double-blind cross-over study indicates that RSH does not improve RS performance compared with RSN in normoxic and hypoxic conditions in endurance-trained subjects. Therefore, caution should be exercised when proposing RSH as an advantageous method to improve exercise performance.
PURPOSE: To compare hemoglobin mass (Hbmass) changes during an 18-d live high-train low (LHTL) altitude training camp in normobaric hypoxia (NH) and hypobaric hypoxia (HH). METHODS: Twenty-eight well-trained male triathletes were split into three groups (NH: n = 10, HH: n = 11, control [CON]: n = 7) and participated in an 18-d LHTL camp. NH and HH slept at 2250 m, whereas CON slept, and all groups trained at altitudes <1200 m. Hbmass was measured in duplicate with the optimized carbon monoxide rebreathing method before (pre-), immediately after (post-) (hypoxic dose: 316 vs 238 h for HH and NH), and at day 13 in HH (230 h, hypoxic dose matched to 18-d NH). Running (3-km run) and cycling (incremental cycling test) performances were measured pre and post. RESULTS: Hbmass increased similar in HH (+4.4%, P < 0.001 at day 13; +4.5%, P < 0.001 at day 18) and NH (+4.1%, P < 0.001) compared with CON (+1.9%, P = 0.08). There was a wide variability in individual Hbmass responses in HH (-0.1% to +10.6%) and NH (-1.4% to +7.7%). Postrunning time decreased in HH (-3.9%, P < 0.001), NH (-3.3%, P < 0.001), and CON (-2.1%, P = 0.03), whereas cycling performance changed nonsignificantly in HH and NH (+2.4%, P > 0.08) and remained unchanged in CON (+0.2%, P = 0.89). CONCLUSION: HH and NH evoked similar Hbmass increases for the same hypoxic dose and after 18-d LHTL. The wide variability in individual Hbmass responses in HH and NH emphasizes the importance of individual Hbmass evaluation of altitude training.
This study examined the effects of 5 weeks (∼60 min/training, 2 days/week) of run-based high-intensity, repeated-sprint ability and explosive strength / agility / sprint training in either normobaric hypoxia (RSH; FIO2 14.3%) or in normoxia (RSN; FIO2 21.0%) on physical performance in 16 highly-trained, under-18 male footballers. For both RSH (n = 8) and RSN (n = 8) groups, lower limb explosive power, sprinting (10 to 40 m) times, maximal aerobic speed, repeated-sprint (10 x 30 m, 30-s rest) and repeated-agility (6 x 20 m, 30-s rest) abilities were evaluated in normoxia before and after supervised training. Lower limb explosive power (+6.5±1.9% vs. +5.0±7.6% for RSH and RSN, respectively; both P<0.001) and performance during maximal sprinting increased (from -6.6±2.2% vs. -4.3±2.6% at 10 m to -1.7±1.7% vs. -1.3±2.3% at 40m for RSH and RSN, respectively; P values ranging from <0.05 to <0.01) to a similar extent in RSH and RSN. Both groups improved best (-3.0±1.7% vs. -2.3±1.8%; both P<0.05) and mean (-3.2±1.7%, P<0.01 vs. -1.9±2.6%, P<0.05 for RSH and RSN, respectively) repeated-sprint times, while sprint decrement did not change. Significant interactions effects (P<0.05) between condition and time were found for repeated-agility ability related-parameters with very likely greater gains (P<0.05) for RSH than RSN (initial sprint: 4.4±1.9% vs. 2.0±1.7% and cumulated times: 4.3±0.6% vs. 2.4±1.7%). Maximal aerobic speed remained unchanged throughout the protocol. In youth highly-trained football players, the addition of ten repeated-sprint training sessions performed in hypoxia vs. normoxia to their regular football practice over a 5-week in-season period was more efficient at enhancing repeated-agility ability (including direction changes), while it had no additional effect on improvements in lower limb explosive power, maximal sprinting and repeated-sprint ability performance.
The effects of hypoxic training on exercise performance remain controversial. Here we tested the hypotheses that i) hypoxic training possesses ergogenic effects at sea-level and altitude, and ii) the benefits are primarily mediated by improved mitochondrial function of skeletal muscle.
We determined aerobic performance (incremental test to exhaustion and time trial for a set amount of work) in moderately-trained subjects undergoing six weeks of endurance training (3-4 times/week, 60 min/session) in normoxia (placebo, n=8) or normobaric hypoxia (FIO2=0.15; n=9) using a double blind and randomized design. Exercise tests were performed in normoxia and acute hypoxia (FIO2=0.15). Skeletal muscle mitochondrial respiratory capacities and electron coupling efficiencies were measured via high-resolution respirometry. Total hemoglobin mass (Hbmass) was assessed by carbon-monoxide rebreathing.
Skeletal muscle respiratory capacity was not altered by training or hypoxia, however electron coupling control respective to fat oxidation slightly diminished with hypoxic training. Hypoxic training did increase Hbmass more than placebo (8.4 vs 3.3%, p=0.02). In normoxia, hypoxic training had no additive effect on maximal measures of oxygen uptake (VO2peak) or time trial performance. In acute hypoxia, hypoxic training conferred no advantage on VO2peak, but tended to enhance time trial performance more than normoxic training (52 versus 32%, p=0.09).
Our data suggest that, in moderately-trained subjects, six weeks of hypoxic training possess no ergogenic effect at sea-level. It is not excluded that hypoxic training might facilitate endurance capacity at moderate altitude, however this issue is still open and needs to be further examined.
Study objectives:
Newcomers at high altitude (> 3,000 m) experience periodic breathing, sleep disturbances, and impaired cognitive performance. Whether similar adverse effects occur at lower elevations is uncertain, although numerous lowlanders travel to moderate altitude for professional or recreational activities. We evaluated the hypothesis that nocturnal breathing, sleep, and cognitive performance of lowlanders are impaired at moderate altitude.
Design:
Randomized crossover trial.
Setting:
University hospital at 490 m, Swiss mountain villages at 1,630 m and 2,590 m.
Participants:
Fifty-one healthy men, median (quartiles) age 24 y (20-28 y), living below 800 m.
Interventions:
Studies at Zurich (490 m) and during 4 consecutive days at 1,630 m and 2,590 m, respectively, 2 days each. The order of altitude exposure was randomized. Polysomnography, psychomotor vigilance tests (PVT), the number back test, several other tests of cognitive performance, and questionnaires were evaluated.
Measurements and results:
The median (quartiles) apnea-hypopnea index at 490 m was 4.6/h (2.3; 7.9), values at 1,630 and 2,590 m, day 1 and 2, respectively, were 7.0/h (4.1; 12.6), 5.4/h (3.5; 10.5), 13.1/h (6.7; 32.1), and 8.0/h (4.4; 23.1); corresponding values of mean nocturnal oxygen saturation were 96% (95; 96), 94% (93; 95), 94% (93; 95), 90% (89; 91), 91% (90; 92), P < 0.05 versus 490 m, all instances. Slow wave sleep on the first night at 2,590 m was 21% (18; 25) versus 24% (20; 27) at 490 m (P < 0.05). Psychomotor vigilance and various other measures of cognitive performance did not change significantly.
Conclusions:
Healthy men acutely exposed during 4 days to hypoxemia at 1,630 m and 2,590 m reveal a considerable amount of periodic breathing and sleep disturbances. However, no significant effects on psychomotor reaction speed or cognitive performance were observed.
Clinical trials registration:
Clinicaltrials.gov: NCT01130948.
Elite athletes often undertake multiple altitude exposures within and between training years in an attempt to improve sea level performance.
To quantify the reproducibility of responses to live high/train low (LHTL) altitude exposure in the same group of athletes.
Sixteen highly trained runners with maximal aerobic power (VO2max) of 73.1 +/- 4.6 and 64.4 +/- 3.2 mL x kg(-1) x min(-1) (mean +/- SD) for males and females, respectively, completed 2 x 3-wk blocks of simulated LHTL (14 h x d(-1), 3000 m) or resided near sea level (600 m) in a controlled study design. Changes in the 4.5-km time trial performance and physiological measures including VO2max, running economy and hemoglobin mass (Hb(mass)) were assessed.
Time trial performance showed small and variable changes after each 3-wk altitude block in both the LHTL (mean [+/-90% confidence limits]: -1.4% [+/-1.1%] and 0.7% [+/-1.3%]) and the control (0.5% [+/-1.5%] and -0.7% [+/-0.8%]) groups. The LHTL group demonstrated reproducible improvements in VO2max (2.1% [+/-2.1%] and 2.1% [+/-3.9%]) and Hb(mass) (2.8% [+/-2.1%] and 2.7% [+/-1.8%]) after each 3-wk block. Compared with those in the control group, the runners in the LHTL group were substantially faster after the first 3-wk block (LHTL - control = -1.9% [+/-1.8%]) and had substantially higher Hb(mass) after the second 3-wk block (4.2% [+/-2.1%]). There was no substantial difference in the change in mean VO2max between the groups after the first (1.2% [+/-3.3%]) or second 3-wk block (1.4% [+/-4.6%]).
Three-week LHTL altitude exposure can induce reproducible mean improvements in VO2max and Hb(mass) in highly trained runners, but changes in time trial performance seem to be more variable. Competitive performance is dependent not only on improvements in physiological capacities that underpin performance but also on a complex interaction of many factors including fitness, fatigue, and motivation.
The principal objective of this study was to test the hypothesis that acclimatization to moderate altitude (2,500 m) plus training at low altitude (1,250 m), "living high-training low," improves sea-level performance in well-trained runners more than an equivalent sea-level or altitude control. Thirty-nine competitive runners (27 men, 12 women) completed 1) a 2-wk lead-in phase, followed by 2) 4 wk of supervised training at sea level; and 3) 4 wk of field training camp randomized to three groups: "high-low" (n = 13), living at moderate altitude (2,500 m) and training at low altitude (1,250 m); "high-high" (n = 13), living and training at moderate altitude (2,500 m); or "low-low" (n = 13), living and training in a mountain environment at sea level (150 m). A 5,000-m time trial was the primary measure of performance; laboratory outcomes included maximal O2 uptake (VO2 max), anaerobic capacity (accumulated O2 deficit), maximal steady state (MSS; ventilatory threshold), running economy, velocity at VO2 max, and blood compartment volumes. Both altitude groups significantly increased VO2 max (5%) in direct proportion to an increase in red cell mass volume (9%; r = 0.37, P < 0.05), neither of which changed in the control. Five-kilometer time was improved by the field training camp only in the high-low group (13.4 +/- 10 s), in direct proportion to the increase in VO2 max (r = 0.65, P < 0.01). Velocity at VO2 max and MSS also improved only in the high-low group. Four weeks of living high-training low improves sea-level running performance in trained runners due to altitude acclimatization (increase in red cell mass volume and VO2 max) and maintenance of sea-level training velocities, most likely accounting for the increase in velocity at VO2 max and MSS.
Moderate-altitude living (2,500 m), combined with low-altitude training (1,250 m) (i.e., live high-train low), results in a significantly greater improvement in maximal O2 uptake (V(02)max) and performance over equivalent sea-level training. Although the mean improvement in group response with this "high-low" training model is clear, the individual response displays a wide variability. To determine the factors that contribute to this variability, 39 collegiate runners (27 men, 12 women) were retrospectively divided into responders (n = 17) and nonresponders (n = 15) to altitude training on the basis of the change in sea-level 5,000-m run time determined before and after 28 days of living at moderate altitude and training at either low or moderate altitude. In addition, 22 elite runners were examined prospectively to confirm the significance of these factors in a separate population. In the retrospective analysis, responders displayed a significantly larger increase in erythropoietin (Epo) concentration after 30 h at altitude compared with nonresponders. After 14 days at altitude, Epo was still elevated in responders but was not significantly different from sea-level values in nonresponders. The Epo response led to a significant increase in total red cell volume and V(O2) max in responders; in contrast, nonresponders did not show a difference in total red cell volume or V(O2)max after altitude training. Nonresponders demonstrated a significant slowing of interval-training velocity at altitude and thus achieved a smaller O2 consumption during those intervals, compared with responders. The acute increases in Epo and V(O2)max were significantly higher in the prospective cohort of responders, compared with nonresponders, to altitude training. In conclusion, after a 28-day altitude training camp, a significant improvement in 5,000-m run performance is, in part, dependent on 1) living at a high enough altitude to achieve a large acute increase in Epo, sufficient to increase the total red cell volume and V(O2)max, and 2) training at a low enough altitude to maintain interval training velocity and O2 flux near sea-level values.
To describe a group of patients who acquired pulmonary edema at a moderate altitude of 1,400 to 2,400 m.
Observational, retrospective chart review (1992-2000) of a series of 52 consecutive patients admitted for high-altitude pulmonary edema (HAPE) that occurred at 1,400 to 2,400 m.
Emergency department of a community hospital in the French Alps (altitude, 500 m).
Vacationing skiers who met criteria for altitude-related pulmonary edema, and in whom other causes (infectious, cardiogenic, neurogenic, and toxic) were excluded. Measurements and results: All patients presented with signs of pulmonary edema. Diagnoses of infectious, cardiogenic, neurogenic, or toxic edema were ruled out in each patient. All patients were hypoxemic and had radiographic signs of pulmonary edema. Virtually all patients (96%) had dyspnea, and most (77%) had moist rales. All patients were treated with supplemental oxygen (3 to 12 L/min), bed rest, moderate fluid restriction, and continuous positive airway pressure. All recovered fully and were discharged after 4 +/- 2 days (mean +/- SD).
This study suggests that HAPE at moderate altitudes is more frequent than usually reported. Patients are likely to be young, vacationing men, with no history of prior disease. The disease has a favorable prognosis, and requires simple treatment and a short hospital stay.