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Individual hemoglobin mass response to normobaric and hypobaric "live high-train low": A one-year crossover study
Abstract
Purpose:
To compare individual hemoglobin mass (Hbmass) changes following a live high-train low (LHTL) altitude training camp under either normobaric hypoxia (NH) or hypobaric hypoxia (HH) conditions in endurance athletes.
Methods:
In a crossover design with a one-year washout, 15 male triathletes randomly performed two 18-d LHTL training camps in either HH or NH. All athletes slept at 2250 m and trained at altitudes < 1200 m. Hbmass was measured in duplicate with the optimized carbon monoxide rebreathing method before (pre-) and immediately after (post-) each 18 d training camp.
Results:
Hbmass increased similarly in HH (916 to 957 g, 4.5 ± 2.2%, P < 0.001) and in NH (918 to 953 g, 3.8 ± 2.6%, P < 0.001). Hbmass changes did not differ between HH and NH (P = 0.42). There was substantial inter-individual variability among subjects to both interventions (i.e., individual responsiveness, or the individual variation in the response to an intervention free of technical noise): 0.9% in HH and 1.7% in NH. However, a correlation between intra-individual delta Hbmass changes (%) in HH and in NH (r = 0.52, P = 0.048) was observed.
Conclusion:
HH and NH evoked similar mean Hbmass increases following LHTL. Among the mean Hbmass changes, there was a notable variation in individual Hbmass response, which tended to be reproducible.
... Hb mass can be estimated with carbon monoxide (CO) rebreathing methods based on the dilution principle, first introduced for humans by Haldane and Smith more than 100 years ago [1]. Since then, the estimation of Hb mass has been successfully applied in various fields, such as altitude exposure [2,3], altitude training [4][5][6][7][8], heat acclimation training [9][10][11] or endurance talent identification in adolescence [12][13][14][15][16]. ...
... The optimised CO rebreathing method (oCO) was introduced in 2005 by Schmidt and Prommer [17] as a very athlete-friendly variant with high reproducibility [17][18][19][20]. This is why this method has been used in many studies [5][6][7][12][13][14]16] showing various important findings for elite sports. Nonetheless, there are at least two critical aspects to the application of the oCO to estimate Hb mass . ...
Recently, a new automated carbon monoxide (CO) rebreathing method (aCO) to estimate haemoglobin mass (Hbmass) was introduced. The aCO method uses the same CO dilution principle as the widely used optimised CO rebreathing method (oCO). The two methods differ in terms of CO administration, body position, and rebreathing time. Whereas with aCO, CO is administered automatically by the system in a supine position of the subject, with oCO, CO is administered manually by an experienced operator with the subject sitting. Therefore, the aim of this study was to quantify possible differences in Hbmass estimated with the two methods. Hbmass was estimated in 18 subjects (9 females, 9 males) with oCO using capillary blood samples (oCOc) and aCO taking simultaneously venous blood samples (aCOv) and capillary blood samples (aCOc). Overall, Hbmass was different between the three measurement procedures (F = 57.55, p < .001). Hbmass was lower (p < .001) for oCOc (737 g ± 179 g) than for both aCOv (825 g ± 189 g, -9.3%) and aCOc (835 g ± 189 g, -10.6%). There was no difference in Hbmass estimated with aCOv and aCOc procedures (p = .12). Three factors can likely explain the 10% difference in Hbmass: differences in calculations (including a factor for myoglobin flux), body position (distribution of CO in blood circulation) during rebreathing, and time of blood sampling. Moreover, the determination of Hbmass with aCO is possible with capillary blood sampling instead of venous blood sampling.
... P < .01). The results in the present and previous studies 2,4,20,28 demonstrated that the altitude tHb-mass response varies due to inter-individual and intra-individual conditions. The physiological explanation for the intra-individual variability may be different baseline conditions including differences in preceding training days, training status, recovery, or health. ...
... Thus, a "responder" and "nonresponder" to altitude training in terms of tHb-mass does not appear to be a fixed trait. 28 Overall, the variability in individual tHb-mass response to hypoxia detected in the present and previous studies emphasizes the importance of evaluating the individual tHb-mass response of an athlete to each altitude training camp. ...
The present study investigated if athletes can be classified as responders or non‐responders based on their individual change in total hemoglobin mass (tHb‐mass) following altitude training while also identifying the potential factors that may affect responsiveness to altitude exposure. Measurements were completed with 59 elite endurance athletes who participated in national team altitude training camps. Fifteen athletes participated the altitude training camp at least twice. Total Hb‐mass using a CO rebreathing method and other blood markers were measured before and after a total of 82 altitude training camps (1350‐2500 m) in 59 athletes. In 46 (56 %) altitude training camps tHb‐mass increased. The amount of positive responses increased to 65 % when only camps above 2000 m were considered. From the fifteen athletes who participated in altitude training camps at least twice, 27 % always had positive tHb‐mass responses, 13 % only negative responses and 60 % both positive and negative responses. Logistic regression analysis showed that altitude was the most significant factor explaining positive tHb‐mass response. Furthermore, male athletes had greater tHb‐mass response than female athletes. In endurance athletes, tHb‐mass is likely to increase after altitude training given that hypoxic stimulus is appropriate. However, great inter‐ and intraindividual variability in tHb‐mass response does not support classification of an athlete permanently as a responder or non‐responder. This variability warrants efforts to control numerous factors affecting an athlete’s response to each altitude training camp.
... As mountain guides often perform long-lasting hiking and climbing tours often without essential food intake, adaptation to prolonged fasting might also help to explain this paradox, which has recently been demonstrated in ultraendurance athletes (Creighton et al., 2018). Finally, prolonged and repeated exposures to moderate and high altitudes (hypoxia), typical for mountaineers and skiers as well, may evoke hematological changes (acclimatization) and some type of hypoxia conditioning, associated with beneficial effects on performance and health (Katayama et al., 2003;Schega et al., 2016;Serebrovskaya and Xi, 2016;Burtscher, 2017;Mallet et al., 2018), and also support improvement and maintenance of aerobic performance (Hauser et al., 2017). Based on human and animal studies, such exposures to hypoxia (altitude) and related conditioning effects (intermittent hypoxia conditioning) may diminish cardio-and cerebrovascular risk factors such as hypertension (Lyamina et al., 2011) by upregulating vascular endothelial growth factor, erythropoietin, and hemoglobin levels (Hauser et al., 2017;Törpel et al., 2019), antioxidants, and nitric oxide (Manukhina et al., 2006), and also by potential suppression of apoptosis ( Jung et al., 2008). ...
... Finally, prolonged and repeated exposures to moderate and high altitudes (hypoxia), typical for mountaineers and skiers as well, may evoke hematological changes (acclimatization) and some type of hypoxia conditioning, associated with beneficial effects on performance and health (Katayama et al., 2003;Schega et al., 2016;Serebrovskaya and Xi, 2016;Burtscher, 2017;Mallet et al., 2018), and also support improvement and maintenance of aerobic performance (Hauser et al., 2017). Based on human and animal studies, such exposures to hypoxia (altitude) and related conditioning effects (intermittent hypoxia conditioning) may diminish cardio-and cerebrovascular risk factors such as hypertension (Lyamina et al., 2011) by upregulating vascular endothelial growth factor, erythropoietin, and hemoglobin levels (Hauser et al., 2017;Törpel et al., 2019), antioxidants, and nitric oxide (Manukhina et al., 2006), and also by potential suppression of apoptosis ( Jung et al., 2008). These observations may also contribute to a higher life expectancy in people living at moderate altitudes, primarily related to reduced mortality from cardiovascular disease and cancer (Faeh et al., 2009;Burtscher, 2016;Thiersch and Swenson, 2018). ...
Puehringer, Reinhard, Martin Berger, Michael Said, and Martin Burtscher. Age-dependent health status and cardiorespiratory fitness in Austrian military mountain guides. High Alt Med Biol 00:000-000, 2020.
Background:
Mountaineering activities (at moderate and high altitudes) require a relatively high level of physical fitness, which may be closely associated with healthy aging. This cross-sectional study was aimed at evaluating the age-dependent health status and fitness level in Austrian military mountain guides.
Methods:
A total of 166 professional mountain guides were recruited for a comprehensive health check and exercise testing. Comparisons were made between 3 different age groups, that is, ≤40 years (n = 74), 41-50 years (n = 70), and >50 years (n = 22). Besides exercise capacity, anthropometric, biomedical, and cardiorespiratory parameters have been assessed.
Results:
None of the assessed parameters differed between age group 1 and 2. A slight increase was observed in the age group 3 concerning body weight, body mass index, blood lipids, blood glucose, and urea levels, and resting systemic blood pressure values. Peak aerobic capacity and maximal heart rates were slightly lower in this age group than the younger groups. When compared with the general population, mountain guides of similar age showed lower prevalence of being overweight, and suffering from systemic hypertension and diabetes.
Conclusions:
Our findings indicate favorable aging of mountain guides occupationally performing mountaineering activities (at moderate and high altitudes), characterized by maintaining a high fitness level and developing reduced cardiovascular risk factors until older than 50 years.
... The concept of altitude or hypoxic training is a common practice for improving aerobic capacity and endurance performance [1]. Several strategies of altitude training, like "live high + train high", "live high + train low" and "live low + train high" have been proposed [2][3][4][5][6][7][8][9][10][11]. They are based on adaptive changes of humans to chronic hypoxia [12]. ...
Intermittent hypoxia training has been proposed as a potent facilitator of hematological adaptability, especially with respect to red blood cell proliferation and hemoglobin concentration. However, the comprehensive physiological implications of intermittent hypoxia training
... Reducing oxygen levels in arterial blood, by environmental manipulation of PiO 2 , stabilises hypoxia-inducible factor 1-alpha (HIF1-α), a transcription factor regulating the coordinated cellular response to hypoxia (Semenza, 2000). This upregulates the transcription of genes implicated in oxygen delivery, including central haematological adaptations induced by chronic hypoxic exposure (Hauser et al., 2017), and further downstream effects of HIF1-α expression which may aid in tissue repair (Kallio, 1998). These putative molecular effects of hypoxic exposure may therefore be of interest with regards to healing mechanisms after an injury has occurred. ...
Recent evidence suggests that different hypoxic modalities might accelerate the rehabilitation process in injured athletes. In this review, the application of hypoxia during rehabilitation from musculoskeletal injury is explored in relation to two principles: (1) facilitating the healing of damaged tissue, and (2) mitigating detraining and inducing training adaptations with a reduced training load. Key literature that explores the underlying mechanisms for these themes is presented, and considerations for practice and future research directions are outlined. For principle (1), passive intermittent hypoxic exposures might accelerate tissue healing through angiogenic and osteogenic mechanisms. Experimental evidence is largely derived from rodent research, so further work is warranted to establish whether clinically meaningful effects can be observed in humans, before optimal protocols are determined (duration, frequency, and hypoxic severity). Regarding principle (2), a hypoxia-related increase in the cardiometabolic stimulus imposed by low-load exercise is appealing for load-compromised athletes. As rehabilitation progresses, a variety of hypoxic modalities can be implemented to enhance adaptation to energy-systems and resistance-based training, and more efficiently return the athlete to competition readiness. While hypoxic modalities seem promising for accelerating musculoskeletal injury rehabilitation in humans, and are already being widely used in practice, a significant gap remains regarding their evidence-based application.
... If CO rebreathing is eventually used for performance enhancement purposes, it would require a disproportionate effort with repeated inhalations of a toxic gas (and the need to strictly limit CO doses to avoid death) for several weeks [5]. Then, putative benefits would not exceed those of an altitude training camp or intermittent hypoxia that could produce improvements safely using hypoxia at real or simulated altitude [10]. CO rebreathing (much alike smoking) should therefore be considered a fully toxic approach towards performance improvement and cannot be supported by coaches or scientists [11]. ...
... Although the potential benefits of altitude training for sea-level performance have been extensively investigated, controlled studies including elite endurance athletes completing altitude training camps under ecologically valid conditions are scarce (Sharma, 2022). Moreover, the wide intra-and inter-individual variability regularly observed in hematological response to prolonged hypoxic exposure encourages further investigation (Hauser et al., 2017;Nummela et al., 2021 Hungary) ( Figure 1). The athletes were in a "pre-competition" phase leading to the WC, which featured as their main competition of the year (20-km or 35-km race walk). ...
Current guidelines for prolonged altitude exposure suggest altitude levels ranging from 2000 to 2500 m to optimize an increase in total hemoglobin mass (Hbmass). However, natural low altitude locations (<2000 m) remain popular, highlighting the interest to investigate any possible benefit of low altitude camps for endurance athletes. Ten elite racewalkers (4 women and 6 men) underwent a 4‐week “live high‐train high” (LHTH) camp at an altitude of 1720 m (PIO2 = 121 mmHg; 20.1°C; 67% relative humidity [RH]), followed by a 3‐week tapering phase (20 m; PIO2 = 150 mmHg; 28.3°C; 53% RH) in preparation for the World Athletics Championships (WC). Venous blood samples were withdrawn weekly during the entire observation period. In addition, blood volumes were determined weekly by carbon monoxide rebreathing during altitude exposure and 2 weeks after return to sea level. High‐level performances were achieved at the WC (five placings among the Top 10 WC races and three all‐time career personal bests). A slight but significant increase in absolute (+1.7%, p = 0.03) and relative Hbmass (+2.3%, p = 0.02) was observed after 4‐week LHTH. In addition, as usually observed during LHTH protocols, weekly training distance (+28%, p = 0.02) and duration (+30%, p = 0.04) significantly increased during altitude compared to the pre‐LHTH period. Therefore, although direct causation cannot be inferred, these results suggest that the combination of increased training load at low altitudes with a subsequent tapering period in a warm environment is a suitable competition‐preparation strategy for elite endurance athletes.
... This considerable within-athlete variability suggests a shift from seeking universal 'best' answers to exploring individual-specific altitude training solutions. Our study highlights that some athletes benefited from relatively moderate hypoxic doses, while others did not, prompting questions about determining the minimum effective dose for each athlete to achieve meaningful gains (Hauser et al., 2017). Due to the lack of pre-screening for iron status in athletes, we cannot exclude the possibility that hematological adaptations, and consequently performance benefits, resulting from altitude camps were compromised by insufficient iron availability (Burtscher et al., 2018). ...
Objectives
To test the hypothesis that ‘live high-base train high-interval train low’ (HiHiLo) altitude training, compared to ‘live low-train high’ (LoHi), yields greater benefits on performance and physiological adaptations.
Methods
Sixteen young male middle-distance runners (age, 17.0 ± 1.5 y; body mass, 58.8 ± 4.9 kg; body height, 176.3 ± 4.3 cm; training years, 3–5 y; training distance per week, 30–60 km.wk ⁻¹ ) with a peak oxygen uptake averaging ~65 ml.min ⁻¹ .kg ⁻¹ trained in a normobaric hypoxia chamber (simulated altitude of ~2,500 m, monitored by heart rate ~170 bpm; thrice weekly) for 3 weeks. During this period, the HiHiLo group ( n = 8) stayed in normobaric hypoxia (at ~2,800 m; 10 h.day ⁻¹ ), while the LoHi group ( n = 8) resided near sea level. Before and immediately after the intervention, peak oxygen uptake and exercise-induced arterial hypoxemia responses (incremental cycle test) as well as running performance and time-domain heart rate variability (5-km time trial) were assessed. Hematological variables were monitored at baseline and on days 1, 7, 14 and 21 during the intervention.
Results
Peak oxygen uptake and running performance did not differ before and after the intervention in either group (all P > 0.05). Exercise-induced arterial hypoxemia responses, measured both at submaximal (240 W) and maximal loads during the incremental test, and log-transformed root mean square of successive R-R intervals during the 4-min post-run recovery period, did not change (all P > 0.05). Hematocrit, mean reticulocyte absolute count and reticulocyte percentage increased above baseline levels on day 21 of the intervention (all P < 0.001), irrespective of group.
Conclusions
Well-trained runners undertaking base training at moderate simulated altitude for 3 weeks, with or without hypoxic residence, showed no performance improvement, also with unchanged time-domain heart rate variability and exercise-induced arterial hypoxemia responses.
... [25] It was then reported that increase of maximal oxygen consumption, performance enhancement and hemoglobin mass were similar between the two conditions in crossover studies. [26,27] Nonetheless, safety considerations should not be neglected. Intermittent HH could induce unfavorable biochemical alterations, including reduced oxidation resistance and heightened lipid peroxidation, potentially impairing vascular endothelial function and vascular hemodynamics. ...
Severe hypoxia can induce a range of systemic disorders; however, surprising resilience can be obtained through sublethal adaptation to hypoxia, a process termed as hypoxic conditioning. A particular form of this strategy, known as intermittent hypoxia conditioning hormesis, alternates exposure to hypoxic and normoxic conditions, facilitating adaptation to reduced oxygen availability. This technique, originally employed in sports and high-altitude medicine, has shown promise in multiple pathologies when applied with calibrated mild to moderate hypoxia and appropriate hypoxic cycles.
Recent studies have extensively investigated the protective role of intermittent hypoxia conditioning and its underlying mechanisms using animal models, demonstrating its potential in organ protection. This involves a range of processes such as reduction of oxidative stress, inflammation, and apoptosis, along with enhancement of hypoxic gene expression, among others.
Given that intermittent hypoxia conditioning fosters beneficial physiological responses across multiple organs and systems, this review presents a comprehensive analysis of existing studies on intermittent hypoxia and its potential advantages in various organs. It aims to draw attention to the possibility of clinically applying intermittent hypoxia conditioning as a multi-organ protective strategy. This review comprehensively discusses the protective effects of intermittent hypoxia across multiple systems, outlines potential procedures for implementing intermittent hypoxia, and provides a brief overview of the potential protective mechanisms of intermittent hypoxia.
... While [Hb] is highly dependent on PV and its variability, total hemoglobin mass (Hbmass) is a relatively stable parameter. It represents the absolute mass of circulating hemoglobin in the body and several studies confirmed its stability in different situations, notably during altitude training camps or with exercise protocols (Eastwood et al., 2008;Garvican et al., 2010;Hauser et al., 2017;Nummela et al., 2021;Pottgiesser et al., 2009). In the context of medical diagnosis, Hbmass measurement provides complementary and relevant information to the CBC. ...
Hemoglobin concentration ([Hb]) is used for the clinical diagnosis of anemia, and in sports as a marker of blood doping. [Hb] is however subject to significant variations mainly due to shifts in plasma volume (PV). This study proposes a newly developed model able to accurately predict total hemoglobin mass (Hbmass) and PV from a single complete blood count (CBC) and anthropometric variables in healthy subject. Seven hundred and sixty-nine CBC coupled to measures of Hbmass and PV using a CO-rebreathing method were used with a machine learning tool to calculate an estimation model. The predictive model resulted in a root mean square error of 33.2 g and 35.6 g for Hbmass, and 179mL and 244mL for PV, in women and men, respectively. Measured and predicted data were significantly correlated (p<0.001) with a coefficient of determination (R2) ranging from 0.76 to 0.90 for Hbmass and PV, in both women and men. The Bland–Altman bias was on average 0.23 for Hbmass and 4.15 for PV. We herewith present a model with a robust prediction potential for Hbmass and PV. Such model would be relevant in providing complementary data in contexts such as the epidemiology of anemia or the individual monitoring of [Hb] in anti-doping.
... 20 It is likely that some athletes will demonstrate a beneficial response using lower hypoxic doses (but still above a critical threshold), while others fail to do so, questioning what a minimum dose should be for each athlete to induce meaningful gains. 21 Measuring the erythropoietin in the blood, 4 either shortly after starting altitude exposure or in a laboratory setting, can be used to identify where athletes may sit on the high-to-low responder continuum. ...
Background:
Altitude training is often regarded as an indispensable tool for the success of elite endurance athletes. Historically, altitude training emerged as a key strategy to prepare for the 1968 Olympics, held at 2300 m in Mexico City, and was limited to the "Live High-Train High" method for endurance athletes aiming for performance gains through improved oxygen transport. This "classical" intervention was modified in 1997 by the "Live High-Train Low" (LHTL) model wherein athletes supplemented acclimatization to chronic hypoxia with high-intensity training at low altitude.
Purpose:
This review discusses important considerations for successful implementation of LHTL camps in elite athletes based on experiences, both published and unpublished, of the authors.
Approach:
The originality of our approach is to discuss 10 key "lessons learned," since the seminal work by Levine and Stray-Gundersen was published in 1997, and focusing on (1) optimal dose, (2) individual responses, (3) iron status, (4) training-load monitoring, (5) wellness and well-being monitoring, (6) timing of the intervention, (7) use of natural versus simulated hypoxia, (8) robustness of adaptative mechanisms versus performance benefits, (9) application for a broad range of athletes, and (10) combination of methods. Successful LHTL strategies implemented by Team USA athletes for podium performance at Olympic Games and/or World Championships are presented.
Conclusions:
The evolution of the LHTL model represents an essential framework for sport science, in which field-driven questions about performance led to critical scientific investigation and subsequent practical implementation of a unique approach to altitude training.
... LHTL was found to enhance erythropoiesis and increase blood oxygen's transport capacity [82,83]. It improves oxygen consumption at a high altitude/hypoxic environment at sea level [67]. ...
Human Acclimatization and therapeutic approaches are the core components for conquering the physiological variations at high altitude (≥2500 m) exposure. The declined atmospheric pressure and reduced partial pressure of oxygen at high altitudes tend to decrease the temperature by several folds. Hypobaric hypoxia is a major threat to humanity at high altitudes, and its potential effects include altitude mountain sickness. On severity, it may lead to the development of conditions like high-altitude cerebral edema (HACE) or high-altitude pulmonary edema (HAPE) and cause unexpected physiological changes in the healthy population of travelers, athletes, soldiers, and low landers while sojourning at high altitude. Previous investigations have been done on long-drawn-out acclimatization strategies such as the staging method to prevent the damage caused by high-altitude hypobaric Hypoxia. Inherent Limitations of this strategy hamper the daily lifestyle and time consuming for people. It is not suitable for the rapid mobilization of people at high altitudes. There is a need to recalibrate acclimatization strategies for improving health protection and adapting to the environmental variations at high altitudes. This narrative review details the geographical changes and physiological changes at high altitudes and presents a framework of acclimatization, pre-acclimatization, and pharmacological aspects of high-altitude survival to enhance the government efficacy and capacity for the strategic planning of acclimatization, use of therapeutics, and safe de-induction from high altitude for minimizing the life loss. It's simply too ambitious for the importance of the present review to reduce life loss, and it can be proved as the most essential aspect of the preparatory phase of high-altitude acclimatization in plateau regions without hampering the daily lifestyle. The application of pre-acclimatization techniques can be a boon for people serving at high altitudes, and it can be a short bridge for the rapid translocation of people at high altitudes by minimizing the acclimatization time.
... While [Hb] is highly dependent on PV and its variability, total hemoglobin mass (Hbmass) is a relatively stable parameter. It represents the absolute mass of circulating Hb in the body and several studies showed its stability in different situations, notably during altitude training camps or with exercise protocols (22)(23)(24)(25)(26). In the context of medical diagnosis, Hbmass measurement provides complementary and relevant information to the CBC. ...
Anemia is a widespread disease commonly diagnosed through hemoglobin concentration ([Hb]) thresholds set by the World Health Organization (WHO). However, [Hb] is subject to significant variations mainly due to shifts in plasma volume (PV) which impair the diagnosis of anemia and other medical conditions. The aim of this study was to develop a model able to accurately predict total hemoglobin mass (Hbmass) and PV based on anthropometric and complete blood count (CBC) analyses. 769 CBC coupled to measures of Hbmass and PV using the CO-rebreathing method were used with a machine learning tool in a numeric computing platform (MATLAB regression learner app) to calculate the model. For the predicted values, root mean square error (RMSE) was of 37.9 g and 50.0 g for Hbmass, and 194 ml and 268 ml for PV, in women and men, respectively. Measured and predicted data were significantly correlated (p<0.001) with the coefficient of determination (R2) ranging from 0.73 to 0.81 for Hbmass, and PV, in both women and men. The bland-altman bias between estimated and measured variables was in average of -0.69 for Hbmass and 0.73 for PV. This study proposes a valid model with a high prediction potential for Hbmass and PV, providing relevant complementary data in numerous contexts. This method can notably bring information applicable to the epidemiology of anemia, particularly in countries with high prevalence or in specific population such as high-altitude communities.
... A topic that could provide some new insights is the issue of intra-and interindividual variability in the response to altitude training, and the underlying mechanisms of these variabilities. Multiple studies have been performed that clearly outline the presence of both intra-and interindividual variability in the response to altitude training (Chapman et al., 1998;Friedmann et al., 2005;McLean et al., 2013a,b;Hauser et al., 2017;Nummela et al., 2021). Interindividual variability is variability, in this case in the response to altitude training, between individuals. ...
Sleep is one of the most important aspects of recovery, and is known to be severely affected by hypoxia. The present position paper focuses on sleep as a strong moderator of the altitude training-response. Indeed, the response to altitude training is highly variable, it is not a fixed and classifiable trait, rather it is a state that is determined by multiple factors (e.g., iron status, altitude dose, pre-intervention hemoglobin mass, training load, and recovery). We present an overview of evidence showing that sleep, and more specifically the prolonged negative impact of altitude on the nocturnal breathing pattern, affecting mainly deep sleep and thus the core of physiological recovery during sleep, could play an important role in intra- and interindividual variability in the altitude training-associated responses in professional and recreational athletes. We conclude our paper with a set of suggested recommendations to customize the application of altitude training to the specific needs and vulnerabilities of each athlete (i.e., primum non nocere). Several factors have been identified (e.g., sex, polymorphisms in the TASK2/KCNK5, NOTCH4 and CAT genes and pre-term birth) to predict individual vulnerabilities to hypoxia-related sleep-disordered breathing. Currently, polysomnography should be the first choice to evaluate an individual’s predisposition to a decrease in deep sleep related to hypoxia. Further interventions, both pharmacological and non-pharmacological, might alleviate the effects of nocturnal hypoxia in those athletes that show most vulnerable.
... The authors also commented that individuals that had the largest responses to lower simulated elevations also had the largest responses to higher altitudes. Similar mean increases and a significant correlation between individual's hemoglobin mass responses after normobaric and hypobaric hypoxic live high train low interventions have been reported (Hauser et al., 2017). A moderate altitude (~2100 m) training camp attended by 12 Australian-Football players on 2 consecutive years found that individuals' EPO responses to the same stimuli were not consistent from one year to the next (McLean et al., 2013). ...
Various health disciplines have expressed a growing interest in personalized medicine in order to achieve better outcomes of medical interventions. The physiological responses to change are often characterized by substantial inter-individual variability both on Earth and even in Space. Such variability is frequently underplayed or ignored in most scientific studies. However, by failing to characterize such variability, vital information regarding the mechanisms that underline such responses, in addition to normal regulatory processes, is potentially lost.
Goals
The proposed new Frontiers Research Topic seeks to provide an opportunity to present, describe and explore inter-individual variability (and methods of assessment) in response to changes in activity levels, gravity loading, nutritional status, pharmaceuticals and exposure to radiation. In the process we hope to provide novel data that can inform fundamental science and also practitioners faced with managing (or even harnessing) such variability. Therefore, the aims of this new Frontiers Research Topic are to provide a platform:
1) to present, describe and explore inter-individual variability in the physiological response to change in fields such as exercise science, gravitational physiology, nutrition, pharmacology and radiation biology;
2) to expose and evaluate potential mechanisms e.g. genetic predispositions contributing to inter-individual variability of physiological responses to change;
3) for statisticians to present novel mathematical approaches to expose and evaluate inter-individual variability of physiological responses to change;
4) to highlight the importance of the exposure and evaluation of inter-individual variability in the physiological responses to change.
Scope and information for Authors
The proposed new Research Topic seeks to investigate inter-individual variability of physiological responses in the following disciplines:
1) Inter-individual variability in response to physical exercise
2) Inter-individual variability in response to gravitational unloading
3) Inter-individual variability in pharmacology
4) Inter-individual variability in response to dietary interventions
5) Inter-individual variability in response to radiation exposure
... While some accounts have shown that the hematological responses to prolonged altitude exposure are highly reproducible, with significant positive associations reported between consecutive measures of hemoglobin mass (Hauser et al., 2017) and serum EPO (Wachsmuth et al., 2013), others have challenged this assumption of consistency. For example, Nummela et al. (2021) observed 9 out of 15 (60%) Finnish national endurance team athletes who completed at least two altitude training camps over a 7-year period to have both positive and negative hemoglobin mass responses (defined as an increase above/below the typical error of the measure = 1.7%). ...
Baranauskas, Marissa N., Timothy J. Fulton, Alyce D. Fly, Bruce J. Martin, Timothy D. Mickleborough, and Robert F. Chapman. High intraindividual variability in the response of serum erythropoietin to multiple simulated altitude exposures. High Alt Med Biol 00:000-000, 2022. Purpose: To evaluate within-subject variability in the serum erythropoietin (EPO) response to multiple simulated altitude exposures. Methods: Seven physically active men and women (age 27 ± 3 years, body mass index = 24.6 ± 4.0 kg/m2) were exposed to normobaric hypoxia (fraction of inspired oxygen [FiO2] = 0.14) for 12 hours on three separate occasions. Serum EPO concentrations were measured before exposure (0 hour), after 6 hours, and after 12 hours in hypoxia. The EPO response to hypoxia was calculated as percent change from 0 to 12 hours (ΔEPO0-12). Results: Exposure time had a significant effect on EPO (p < 0.001) with concentrations increasing 3.2 ± 1.3 mIU/ml from 0 to 6 hours (p = 0.034) and 4.7 ± 1.2 mIU/ml from 0 to 12 hours (p = 0.001). Group mean ΔEPO0-12 remained unchanged (p = 0.688) between the three exposures; however, there was considerable intraindividual variability in EPO responses. The intrasubject coefficient of variation for ΔEPO0-12 was 61% ± 28% (range: 17%-103%) with intrasubject associations ranging r = 0.052 to r = 0.651 between repeated exposures. Conclusions: Athletes who routinely supplement training with simulated altitude methods (e.g., hypoxic tents) should expect inconsistent EPO responses to intermittent exposures lasting ≤12 hours.
... The loss of plasma water may partly result from reduced aldosterone activity and increased levels of atrial natriuretic peptide, and seems to persist for months. The erythropoietic response and the elevated O 2 transport capacity are of particular interest in athletes who sojourn for weeks at high altitude/in hypoxia so as to improve aerobic performance at sea level (86). ...
Significance:
Oxygen is indispensable for aerobic life but its utilization exposes cells and tissues to oxidative stress; thus, tight regulation of cellular, tissue and systemic oxygen concentrations is crucial. Here, we review the current understanding of how the human organism (mal-)adapts to low (hypoxia) and high (hyperoxia) oxygen levels and how these adaptations may be harnessed as therapeutic or performance enhancing strategies at the systemic level. Recent Advances: Hyperbaric oxygen therapy is already a cornerstone of modern medicine and the application of mild hypoxia, i.e., hypoxia conditioning, to strengthen the resilience of organs or the whole body to severe hypoxic insults is important preparation for high-altitude sojourns or to protect the cardiovascular system from hypoxic/ischemic damage. Many other applications of adaptations to hypo- and/or hyperoxia are only just emerging. Hypoxia conditioning - sometimes in combination with hyperoxic interventions - is gaining traction for the treatment of chronic diseases, including numerous neurological disorders, and for performance enhancement.
Critical issues:
The dose- and intensity-dependent effects of varying oxygen concentrations render hypoxia- and/or hyperoxia-based interventions potentially highly beneficial, yet hazardous, although the risks vs. benefits are as yet ill-defined.
Future directions:
The field of low and high oxygen conditioning is expanding rapidly and novel applications are increasingly recognized, e.g., the modulation of aging processes, mood disorders or metabolic diseases. To advance hypoxia/hyperoxia conditioning to clinical applications, more research on the effects of the intensity, duration and frequency of altered oxygen concentrations, as well as on individual vulnerabilities to such interventions, is paramount.
... The authors also commented that individuals that had the largest responses to lower simulated elevations also had the largest responses to higher altitudes. Similar mean increases and a significant correlation between individual's hemoglobin mass responses after normobaric and hypobaric hypoxic live high train low interventions have been reported (Hauser et al., 2017). A moderate altitude (~2100 m) training camp attended by 12 Australian-Football players on 2 consecutive years found that individuals' EPO responses to the same stimuli were not consistent from one year to the next (McLean et al., 2013). ...
Hematological changes are commonly observed following prolonged exposure to hypoxia and bed rest. Typically, such responses have been reported as means and standard deviations, however, investigation into the responses of individuals is insufficient. Therefore, the present study retrospectively assessed individual variation in the hematological responses to severe inactivity (bed rest) and hypoxia. The data were derived from three-bed rest projects: two 10-d (LunHab project: 8 males; FemHab project: 12 females), and one 21-d (PlanHab project: 11 males). Each project comprised a normoxic bed rest (NBR; PIO2=133mmHg) and hypoxic bed rest (HBR; PIO2=91mmHg) intervention, where the subjects were confined in the Planica facility (Rateče, Slovenia). During the HBR intervention, subjects were exposed to normobaric hypoxia equivalent to an altitude of 4,000m. NBR and HBR interventions were conducted in a random order and separated by a washout period. Blood was drawn prior to (Pre), during, and post bed rest (R1, R2, R4) to analyze the individual variation in the responses of red blood cells (RBC), erythropoietin (EPO), and reticulocytes (Rct) to bed rest and hypoxia. No significant differences were found in the mean ∆(Pre-Post) values of EPO across projects (LunHab, FemHab, and PlanHab; p>0.05), however, female EPO responses to NBR (Range - 17.39, IQR – 12.97 mIU.ml⁻¹) and HBR (Range – 49.00, IQR – 10.91 mIU.ml⁻¹) were larger than males (LunHab NBR Range – 4.60, IQR – 2.03; HBR Range – 7.10, IQR – 2.78; PlanHab NBR Range – 7.23, IQR – 1.37; HBR Range – 9.72, IQR – 4.91 mIU.ml⁻¹). Bed rest duration had no impact on the heterogeneity of EPO, Rct, and RBC responses (10-d v 21-d). The resultant hematological changes that occur during NBR and HBR are not proportional to the acute EPO response. The following cascade of hematological responses to NBR and HBR suggests that the source of variability in the present data is due to mechanisms related to hypoxia as opposed to inactivity alone. Studies investigating hematological changes should structure their study design to explore these mechanistic responses and elucidate the discord between the EPO response and hematological cascade to fully assess heterogeneity.
... kg −1 , can be accompanied by a significant change in aerobic capacity (Schmidt and Prommer, 2010). To that extent we confirmed the previously reported link between absolute Hbmass and aerobic capacity in elite cyclists (Garvican et al., 2011;Hauser et al., 2017). It could therefore be argued that Hbmass would be a valid marker to complement the ABP analysis. ...
The hematological module of the Athlete Biological Passport (ABP) is used in elite sport for antidoping purposes. Its aim is to better target athletes for testing and to indirectly detect blood doping. The ABP allows to monitor hematological variations in athletes using selected primary blood biomarkers [hemoglobin concentration (Hb) and reticulocyte percentage (Ret%)] with an adaptive Bayesian model to set individual upper and lower limits. If values fall outside the individual limits, an athlete may be further targeted and ultimately sanctioned. Since (Hb) varies with plasma volume (PV) fluctuations, possibly caused by training load changes, we investigated the putative influence of acute and chronic training load changes on the ABP variables. Monthly blood samples were collected over one year in 10 male elite cyclists (25.6 ± 3.4 years, 181 ± 4 cm, 71.3 ± 4.9 kg, 6.7 ± 0.8 W.kg−1 5-min maximal power output) to calculate individual ABP profiles and monitor hematological variables. Total hemoglobin mass (Hbmass) and PV were additionally measured by carbon monoxide rebreathing. Acute and chronic training loads–respectively 5 and 42 days before sampling–were calculated considering duration and intensity (training stress score, TSSTM). (Hb) averaged 14.2 ± 0.0 (mean ± SD) g.dL−1 (range: 13.3–15.5 g·dl−1) over the study with significant changes over time (P = 0.004). Hbmass was 1030 ± 87 g (range: 842–1116 g) with no significant variations over time (P = 0.118), whereas PV was 4309 ± 350 mL (range: 3,688–4,751 mL) with a time-effect observed over the study time (P = 0.014). Higher acute–but not chronic—training loads were associated with significantly decreased (Hb) (P <0.001). Although individual hematological variations were observed, all ABP variables remained within the individually calculated limits. Our results support that acute training load variations significantly affect (Hb), likely due to short-term PV fluctuations, underlining the importance of considering training load when interpreting individual ABP variations for anti-doping purposes.
... Il est tout aussi possible de réduire la FiO 2 à un pourcentage défini, par extraction d'O 2 ou ajout de diazote, pour atteindre la PIO 2 ciblée sans diminuer la pression atmosphérique : c'est l'hypoxie normobare. . En revanche l'augmentation de la masse d'Hb est similaire entre les deux types d'hypoxie (Hauser et al. 2016(Hauser et al. , 2017. De plus, un autre facteur de modulation des réponses de l'organisme doit être considéré : la durée du stress. ...
L’hypoxémie induite à l’exercice (HIE) est un phénomène qui est caractérisé par une chute de pression et de saturation artérielle en oxygène. La HIE touche les athlètes d'endurance. A force d’entrainement, les limites des systèmes cardiaque et musculaire sont repoussées et celles du système pulmonaire apparaissent. La prévalence de la HIE est de plus de 70% chez les athlètes lors d’un effort de course à pied. Or, les athlètes d’endurance sont les plus susceptibles de performer en altitude que ce soit dans le cadre d’une compétition, d’une préparation ou d’un stage d’entrainement. La chute de la pression atmosphérique rencontrée lors de l’élévation de l’altitude entraine une diminution de la quantité d’oxygène dans l’organisme qui constitue un vrai stress, le stress hypoxique. Pour faire face à ce dernier, l’organisme met en place une série d’adaptations visant à maintenir un apport en oxygène suffisant pour les organes. Lors d’un exercice au niveau de la mer les athlètes HIE atteignent les mêmes consommations maximales d’oxygène que les non-HIE, en revanche l’environnement délétère pour la performance que représente l’altitude, pourrait avoir de plus lourdes conséquences sur les athlètes HIE. Les effets de la HIE et de l’altitude pourraient se potentialiser et accroitre la réduction de la disponibilité de l’oxygène dans l’organisme. L’objectif de ce projet est de tester l’hypothèse que les réponses à l’exercice au niveau de la mer et en altitude sont différentes entre des athlètes HIE et non-HIE. Pour cela nous avons étudié les réponses à l’exercice en normoxie et après une exposition à l’altitude modérée aiguë (de quelques minutes à quelques heures) et prolongée (après 5 jours). La première étude montre une augmentation de la désoxygénation cérébrale et une diminution de l’oxygénation musculaire lors de l’exercice en normoxie, ainsi qu’une inadaptation lors de l’effort en hypoxie aiguë aux niveaux musculaire et cérébral. Les études 2 et 3 rapportent des réponses spécifiques à l’exercice, mais également au repos, lors des cinq premiers jours d’exposition en altitude. En effet, dès le repos les athlètes HIE ont des saturations en oxygène plus basses que les athlètes contrôles. Malgré la persistance de la HIE, des mécanismes compensatoires semblent être mis en place aux niveaux cérébral et cardiaque, éventuellement médiés par une balance pro-antioxydant différente. Ces derniers permettent l’atteinte de performances similaires au groupe contrôle après 1 et 5 jours d’exposition. L’étude 4 montre que la viscosité sanguine et l’hémodynamique pulmonaire ne sont pas impliquées dans la chute de saturation de repos plus prononcée des athlètes EIH au cours de l’exposition en altitude. L’étude 5 semble indiquer une réponse vasodilatatrice spécifique chez les athlètes HIE au niveau de la mer et après 5 jours en altitude. Il ressort de ce travail de thèse que la HIE réduit la performance en hypoxie aiguë et entraine des réponses spécifiques à l’exercice en normoxie et en hypoxie, sans doute dans le but de contrebalancer la chute de saturation en oxygène. Il est donc primordial de prendre en compte ce phénomène pour la performance en hypoxie, et d’étudier et comprendre ses interactions avec les différentes modalités d’entrainement, notamment en altitude.
... Beyond genetic attributes, individual physiological characteristics and adaptative responses to chronic hypoxia (slow vs. fast responders) likely influence the timing for peak performance for each athlete. It is also likely that some athletes will demonstrate a beneficial response using lower hypoxic doses, when others fail to do so, questioning what a minimum dose should be for each athlete to induce meaningful gains (Hauser et al. 2017). This information should be considered for the planning of return to sea level, and decide whether adding hypoxic re-exposure or not, after altitude training. ...
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.
... kg -1 , can be accompanied by a significant change in aerobic capacity (Schmidt et al., 2010). To that extent we confirmed the previously reported link between absolute Hbmass and aerobic capacity in elite cyclists (Garvican et al., 2011;Hauser et al., 2017). It could therefore be argued that Hbmass would be a valid marker to complement the ABP analysis. ...
The hematological module of the Athlete Biological Passport (ABP) is used in elite sport for antidoping purposes. Its aim is to better target athletes for testing and to indirectly detect blood doping. The ABP allows to monitor hematological variations in athletes using selected primary blood biomarkers (hemoglobin concentration ([Hb] and reticulocyte percentage (Ret%)) with an adaptive Bayesian model to set individual upper and lower limits. If values fall without the individual limits, an athlete may be further targeted and ultimately sanctioned.
Since [Hb] and Ret% vary with plasma volume (PV) fluctuations, possibly caused by training load changes, we investigated the putative influence of acute and chronic training load changes on the ABP variables.
Monthly blood samples were collected over one year in 10 elite cyclists (25.6 ± 3.4 yrs, 181 ± 4 cm, 71.3 ± 4.9 kg, 6.7 ± 0.8 W.kg ⁻¹ 5-min maximal power output) to calculate individual ABP profiles and monitor hematological variables. Total hemoglobin mass (Hbmass) and PV were additionally measured by carbon monoxide rebreathing. Acute and chronic training loads – respectively 5 and 42 days before sampling – were calculated considering duration and intensity (training stress score, TSS™).
[Hb] averaged 14.2 ± 0.0 (mean ± SD) g.dL ⁻¹ (range: 13.3 to 15.5 g·dl ⁻¹ ) over the study with significant changes over time ( P = 0.004). Hbmass was 1’030 ± 87 g (range: 842 to 1116 g) with no significant variations over time ( P = 0.118), whereas PV was 4309 ± 350 mL (range: 3688 to 4751 mL) with a time-effect observed over the study time ( P = 0.014). Higher acute – but not chronic – training loads were associated with significantly decreased [Hb] ( P <0.001). Although individual hematological variations were observed, all ABP variables remained within the individually calculated limits.
Our results support that acute training load variations significantly affect [Hb], likely due to short-term PV fluctuations, underlining the importance of considering training load when interpreting individual ABP variations for anti-doping purposes.
... One of the best known effects of HIF-2α stabilisation is its ability to increase the rate of haematopoiesis through the up-regulation of erythropoietin (EPO) (Haase 2013), the primary hormonal regulator of red blood cell production (Jelkmann 2011). Currently, most hypoxic conditioning approaches have been designed to increase oxygencarrying capacity in athletes (Richalet and Gore 2008;Rodriguez et al. 2015;Ramos-Campo et al. 2015;Levine and Stray-Gundersen 1997;Hauser et al. 2017) or mountaineers, with the hope of improving sea-level performance (Lundby et al. 2012) or acclimatization to altitude (Muza et al. 2010). ...
Purpose
The purpose of this single-blind, repeated measures study was to investigate the effect of two hypoxic patterns, continuous or intermittent on key markers of haematological adaptation, stress and cardiac damage in healthy senior participants.
Methods
Fifteen healthy senior participants each followed a three-phase protocol over 3 consecutive weeks: (1) 5 consecutive days of breathing room air without a mask (2) 5 days of normoxic mask breathing (sham, FiO2 = 21%) (3) 5 days of intermittent hypoxia (IH) tailored to achieve a mean peripheral oxygen saturation (SpO2) of 85% during ~ 70 min of cumulative exposure to hypoxia. After a 5-month washout period, participants were recalled to undertake continuous hypoxia (CH, SpO2 = 85%, ~ 70 min). 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 OFF-score (i.e. ) were measured.
Results
RBCc only increased by day 5 of IH treatment compared to day 5 baseline values (+ 7.7%, p < 0.01) and day 5 Sham values (+ 12.9%, p < 0.01). [Hb] only increased by day 5 of IH treatment compared to day 5 baseline values (+ 14.7%, p < 0.01) and day 5 Sham values (+ 14.3%, p < 0.01). Hct (+ 12.7%, p < 0.01) and the OFF-score (p < 0.05) increased only during the final day of IH treatment. No difference was observed in S-IgA, cortisol or cTnT following IH or CH.
Conclusion
These results revealed that inherent differences in the IH and CH hypoxic patterns could provide crucial components required to trigger hematological changes in senior individuals, without eliciting immunological stress responses or damaging the myocardium.
... Loepky et al. 1997;Beidleman et al. 2014) or not in favour (e.g. Richard et al. 2014;Bourdillon et al. 2017;Hauser et al. 2017;Woods et al. 2017) of a specific effect of barometric pressure for a given P O2 . Since these previous studies, no convincing mechanistic hypothesis has been put forward to explain the possible difference between hypobaric and normobaric hypoxia. ...
... On the contrary, a hypoxic exposure should exceed 200 h to elicit haematological adaptations (i.e. 225 h in the study by Hauser et al. (2017)). This is why the participants in the present study were confined for 230 h at a simulated altitude of ~ 4000 m and were training every day in the heat for 90 min. ...
Purpose: Hypoxic acclimation enhances convective oxygen delivery to the muscles. Heat acclimation-elicited thermoregulatory benefits have been suggested not to be negated by adding daily exposure to hypoxia. Whether concomitant acclimation to both heat and hypoxia offers a synergistic enhancement of aerobic performance in thermoneutral or hot conditions remains unresolved.
Methods: Eight young males (V̇O2max: 51.6±4.6 mL·min-1·kg-1) underwent a 10-day normobaric hypoxic confinement (FiO2 = 0.14) interspersed with daily 90-min normoxic controlled-hyperthermia (target rectal temperature: 38.5°C) exercise sessions. Prior to, and following the confinement, the participants conducted a 30-min steady-state exercise followed by incremental exercise to exhaustion on a cycle ergometer in thermoneutral normoxic (NOR), thermoneutral hypoxic (FiO2 = 0.14; HYP) and hot (35°C, 50% relative humidity; HE) conditions in a randomized and counterbalanced order. The steady-state exercise was performed at 40% NOR peak power output (Wpeak) to evaluate thermoregulatory function. Blood samples were obtained from an antecubital vein before, on days 1 and 10, and the first day post-acclimation.
Results: V̇O2max and ventilatory thresholds were not modified in any environment following acclimation. Wpeak increased by 6.3±3.4% in NOR and 4.0±4.9% in HE, respectively. The magnitude and gain of the forehead sweating response were augmented in HE post-acclimation. EPO increased from baseline (17.8±7.0 mIU·mL-1) by 10.7±8.8 mIU·mL-1 on day 1 but returned to baseline levels by day 10 (15.7±5.9 mIU·mL-1).
Discussion: A 10-day combined heat and hypoxic acclimation conferred only minor benefits in aerobic performance and thermoregulation in thermoneutral or hot conditions. Thus, adoption of such a protocol does not seem warranted.
... The authors therefore suggested completing a LHTL protocol when travel to altitude prior to competition isn't possible. Given the typical NH outcomes, such as significant increases in Hb mass [32,122,123,132,133], and the fact that some elite endurance athletes and coaches are already strategically implementing NH prior to natural altitude, it can be hypothesized that this protocol would provide an improvement, but this requires scientific validation (Fig. 2). ...
Since the 1960s there has been an escalation in the purposeful utilization of altitude to enhance endurance athletic performance. This has been mirrored by a parallel intensification in research pursuits to elucidate hypoxia-induced adaptive mechanisms and substantiate optimal altitude protocols (e.g., hypoxic dose, duration, timing, and confounding factors such as training load periodization, health status, individual response, and nutritional considerations). The majority of the research and the field-based rationale for altitude has focused on hematological outcomes, where hypoxia causes an increased erythropoietic response resulting in augmented hemoglobin mass. Hypoxia-induced non-hematological adaptations, such as mitochondrial gene expression and enhanced muscle buffering capacity may also impact athletic performance, but research in elite endurance athletes is limited. However, despite significant scientific progress in our understanding of hypobaric hypoxia (natural altitude) and normobaric hypoxia (simulated altitude), elite endurance athletes and coaches still tend to be trailblazers at the coal face of cutting-edge altitude application to optimize individual performance, and they already implement novel altitude training interventions and progressive periodization and monitoring approaches. Published and field-based data strongly suggest that altitude training in elite endurance athletes should follow a long- and short-term periodized approach, integrating exercise training and recovery manipulation, performance peaking, adaptation monitoring, nutritional approaches, and the use of normobaric hypoxia in conjunction with terrestrial altitude. Future research should focus on the long-term effects of accumulated altitude training through repeated exposures, the interactions between altitude and other components of a periodized approach to elite athletic preparation, and the time course of non-hematological hypoxic adaptation and de-adaptation, and the potential differences in exercise-induced altitude adaptations between different modes of exercise.
... The potential underlying mechanisms for improved exercise performance following LHTL include increase in erythropoiesis and blood oxygen transporting capacity (Hauser et al., 2017;Levine and Stray-Gunderson, 1997;. This translates into increased maximal oxygen consumption (VO2max) while residing in an altitude/hypoxic environment, and there is a possibility that the increased exercise intensity in competitions and enhanced VO 2 max will be maintained at sea level (Levine, 2002;Schmitt et al., 2006;Wilber, 2007). ...
Living high-training low (LHTL) is performed by competitive athletes expecting to improve their performance in competitions at sea level. However, the beneficial effects of LHTL remain controversial. We sought to investigate whether 21 days of LHTL performed at a 3,000 m simulated altitude (fraction of inspired oxygen [FIO2]=14.5%) and at sea level can improve hematologi-cal parameters, exercise economy and metabolism, hemodynamic function, and exercise performance compared with living low-training low (LLTL) among competitive athletes. All participants (age = 23.5 ± 2.1 years, maximal oxygen consumption [VO2max] = 55.6 ± 2.5 mLꞏkg-1 ꞏmin-1 , 3,000 m time trial perfor-mance=583.7 ± 22.9 seconds) were randomly assigned to undergo LHTL (n = 12) or LLTL (n = 12) and evaluated before and after the 21 days of intervention. During the 21-day intervention period, the weekly routine for all athletes included 6-day training and 1-day rest. The daily training programs consisted of >4 hours of various exercise programs (i.e., jogging, high-speed running, interval running, and 3,000 m or 5,000-m time trial). The LHTL group resided in a simulated environmental chamber (FIO2 = 14.5%) for >12 hours per day and the LLTL group at sea level under comfortable conditions. The hematological parameters showed no significant interaction. However, LHTL yielded more improved exercise economy, metabolic parameters (oxygen con-sumption=-152.7 vs 32.4 mLꞏkg-1 ꞏ30min-1 , η 2 = 0.457, p = 0.000; tissue oxygenation index=6.18 vs .66%, η 2 = 0.250, p = 0.013), and hemodynamic function (heart rate =-234.5 vs-49.7 beatsꞏ30min-1 , η 2 = 0.172, p = 0.044; stroke volume = 136.4 vs-120.5 mL/30 min, η 2 = 0.191, p = 0.033) during 30 minutes of submaximal cycle ergometer exercise corresponding to 80% maximal heart rate before training than did LLTL. Regarding exercise performance, LHTL also yielded more improved VO2max (5.40 vs 2.35 mLꞏkg-1 ꞏmin-1 , η 2 = 0.527, p = 0.000) and 3,000 m time trial performance (-34.0 vs-19.5 seconds, η 2 = 0.527, p = 0.000) than did LLTL. These results indicate that compared with LLTL, LHTL can have favorable effects on exercise performance by improving exercise economy and hemodynamic function in competitive runners.
... Third, since the recent debate about the existence of different physiological responses between hypobaric (HH) and normobaric hypoxia (NH), it has been argued that sleeping in HH during LHTL would induce greater performance gains than sleeping in NH (6). However, the latest LHTL-related studies seem to indicate that sleeping pattern is more altered in HH versus NH (7), while evoking a similar mean increase in hemoglobin mass (8). This merits further focus on the topic. ...
... The magnitude of increase depends on absolute altitude and duration of stay (Garvican et al., 2012;Rasmussen et al., 2013). However, there is great variability in the erythropoietic response to HA (Chapman et al., 1998;Hauser et al., 2017). This aspect is of particular importance in athletes who chose training at HA to improve aerobic performance. ...
Living, working and exercising in extreme terrestrial environments are challenging tasks even for healthy humans of the modern new age. The issue is not just survival in remote environments but rather the achievement of optimal performance in everyday life, occupation, and sports. Various adaptive biological processes can take place to cope with the specific stressors of extreme terrestrial environments like cold, heat, and hypoxia (high altitude). This review provides an overview of the physiological and morphological aspects of adaptive responses in these environmental stressors at the level of organs, tissues, and cells. Furthermore, adjustments existing in native people living in such extreme conditions on the earth as well as acute adaptive responses in newcomers are discussed. These insights into general adaptability of humans are complemented by outcomes of specific acclimatization/acclimation studies adding important information how to cope appropriately with extreme environmental temperatures and hypoxia.
... In this context, serum EPO measurement may also have been beneficial. Nonetheless, the LHTL protocol employed in the present study is a popular training protocol amongst athletes and remains practically relevant In addition, whilst the Hbmass response evoked by hypobaric hypoxia is expected to be similar to a matched dose of normobaric hypoxia (40); future research should investigate the responses of ERFE and hepcidin during both simulated-and naturalaltitude training camps. ...
Purpose:
Iron is integral for erythropoietic adaptation to hypoxia, yet the importance of supplementary iron compared to existing stores is poorly understood. The aim of the present study was to compare the magnitude of the haemoglobin mass (Hbmass) response to altitude in athletes supplemented with intravenous (IV), oral or placebo iron supplementation.
Methods:
Thirty-four, non-anaemic, endurance-trained athletes completed 3 weeks of simulated altitude (3000 m, 14h.d), receiving either 2-3 bolus iron injections (ferric carboxymaltose), daily oral iron supplementation (ferrous sulphate) or a placebo, commencing 2 weeks prior to and throughout altitude exposure. Hbmass and markers of iron regulation were assessed at baseline (day -14), immediately prior to (day 0), weekly during (days 8, 15), and immediately, 1, 3 and 6 weeks after the completion of altitude exposure (days 22, 28, 42 and 63).
Results:
Hbmass significantly increased following altitude in IV (Mean%, [90% CI]: 3.7%, [2.8, 4.7]) and oral (3.2%, [2.2, 4.2]), and remained elevated at 7 days post-altitude in oral (2.9%, [1.5, 4.3]) and 21 days post in IV (3.0%, [1.5, 4.6]). Hbmass was not significantly higher than baseline at any time point in placebo.
Conclusion:
Iron supplementation appears necessary for optimal erythropoietic adaptation to altitude exposure. Intravenous iron supplementation during three weeks of simulated LHTL altitude training offered no additional benefit in terms of the magnitude of the erythropoietic response for non-anaemic endurance athletes compared to oral supplementation.
... Live high-train low (LHTL) is a recurrent strategy among athletes to improve their endurance performance [132]. To assess the effect of this strategy on hepcidin metabolism, Govus et al. [71] analyzed serum hepcidin responses to an intervallic endurance session (six series of 1000 m of running at 90% VO2peak) in hypoxia (FIO2 ~0.155) or normoxic conditions (600 m of altitude), before and after 11 days of LHTL. ...
Iron deficiency is a frequent and multifactorial disorder in the career of athletes, particularly in females. Exercise-induced disturbances in iron homeostasis produce deleterious effects on performance and adaptation to training; thus, the identification of strategies that restore or maintain iron homeostasis in athletes is required. Hepcidin is a liver-derived hormone that degrades the ferroportin transport channel, thus reducing the ability of macrophages to recycle damaged iron, and decreasing iron availability. Although it has been suggested that the circulating fraction of hepcidin increases during early post-exercise recovery (~3 h), it remains unknown how an acute exercise bout may modify the circulating expression of hepcidin. Therefore, the current review aims to determine the post-exercise expression of serum hepcidin in response to a single session of exercise. The review was carried out in the Dialnet, Elsevier, Medline, Pubmed, Scielo and SPORTDiscus databases, using hepcidin (and "exercise" or "sport" or "physical activity") as a strategy of search. A total of 19 articles were included in the review after the application of the inclusion/exclusion criteria. This search found that a single session of endurance exercise (intervallic or continuous) at moderate or vigorous intensity (60-90% VO2peak) stimulates an increase in the circulating levels of hepcidin between 0 h and 6 h after the end of the exercise bout, peaking at ~3 h post-exercise. The magnitude of the response of hepcidin to exercise seems to be dependent on the pre-exercise status of iron (ferritin) and inflammation (IL-6). Moreover, oxygen disturbances and the activation of a hypoxia-induced factor during or after exercise may stimulate a reduction of hepcidin expression. Meanwhile, cranberry flavonoids supplementation promotes an anti-oxidant effect that may facilitate the post-exercise expression of hepcidin. Further studies are required to explore the effect of resistance exercise on hepcidin expression.
... In a particular sport (e.g. endurance or team sports), considerable individual variation in Hb mass response to altitude training has been reported (Friedmann et al., 2005;Garvican et al., 2012;Siebenmann et al., 2012;Garvican Lewis et al., 2013;Wachsmuth et al., 2013b) and quantified as a standard deviation (SD) from the mean change of ±1.7% to ±2.2% Hauser et al., 2017). Although sources of this variability still remain unclear, aspects such as erythropoietic response to hypoxia (Chapman et al., 1998;Friedmann et al., 2005), genetic predisposition , residual fatigue and training history (Garvican et al., 2007) and/or intra-individual conditions (Wachsmuth et al., 2013b) likely play a role. ...
New Findings
What is the central question of this study?
It has been assumed that athletes embarking on an ‘live high–train low’ (LHTL) camp with already high initial haemoglobin mass (Hb mass ) have a limited ability to increase their Hb mass further post‐intervention. Therefore, the relationship between initial Hb mass and post‐intervention increase was tested with duplicate Hb mass measures and comparable hypoxic doses in male athletes.
What is the main finding and its importance?
There were trivial to moderate inverse relationships between initial Hb mass and percentage Hb mass increase in endurance and team‐sport athletes after the LHTL camp, indicating that even athletes with higher initial Hb mass can reasonably expect Hb mass gains post‐LHTL.
It has been proposed that athletes with high initial values of haemoglobin mass (Hb mass ) will have a smaller Hb mass increase in response to ‘live high–train low’ (LHTL) altitude training. To verify this assumption, the relationship between initial absolute and relative Hb mass values and their respective Hb mass increase following LHTL in male endurance and team‐sport athletes was investigated. Overall, 58 male athletes (35 well‐trained endurance athletes and 23 elite male field hockey players) undertook an LHTL training camp with similar hypoxic doses (200–230 h). The Hb mass was measured in duplicate pre‐ and post‐LHTL by the carbon monoxide rebreathing method. Although there was no relationship ( r = 0.02, P = 0.91) between initial absolute Hb mass (in grams) and the percentage increase in absolute Hb mass , a moderate relationship ( r = −0.31, P = 0.02) between initial relative Hb mass (in grams per kilogram) and the percentage increase in relative Hb mass was detected. Mean absolute and relative Hb mass increased to a similar extent ( P ≥ 0.81) in endurance (from 916 ± 88 to 951 ± 96 g, +3.8%, P < 0.001 and from 13.1 ± 1.2 to 13.6 ± 1.1 g kg ⁻¹ , +4.1%, P < 0.001, respectively) and team‐sport athletes (from 920 ± 120 to 957 ± 127 g, +4.0%, P < 0.001 and from 11.9 ± 0.9 to 12.3 ± 0.9 g kg ⁻¹ , +4.0%, P < 0.001, respectively) after LHTL. The direct comparison study using individual data of male endurance and team‐sport athletes and strict methodological control (duplicate Hb mass measures and matched hypoxic dose) indicated that even athletes with higher initial Hb mass can reasonably expect Hb mass gain post‐LHTL.
... Yet, in recent years, this model has been challenged and many differences between the effects of NH and hypobaric hypoxia (HH, "real altitude") have been reported (Girard et al. 2012), e.g. lower arterial oxygen saturation (Saugy et al. 2014;Coppel et al. 2015) and endurance performance (Saugy et al. 2016a), larger sleep disorders (Heinzer et al. 2016) and oxidative stress (Ribon et al. 2016), and more severe acute mountain sickness symptoms (DiPasquale et al. 2016) in HH compared to NH, while no difference has been demonstrated in the total haemoglobin mass following a "live-high train-low" (LHTL) training prescription (Hauser et al. 2017). Altogether, HH appears to be a stronger stimulus than NH for a given hypoxic level. ...
Abstract
Normobaric hypoxia (NH) is used as a surrogate for hypobaric hypoxia (HH). Recent studies reported physiological differences between NH and HH. Baroreflex sensitivity (BRS) decreases at altitude or following intense training. However, until now no study compared the acute and chronic changes of BRS in NH vs. HH. First, BRS was assessed in 13 healthy male subjects prior and after 20 h of exposure at 3450m (study 1), and second in 15 well-trained athletes prior and after 18 days of “Live-High Train-Low” (LHTL) at 2250m (study 2) in NH vs. HH. BRS decreased (p<0.05) to the same extent in NH and HH after 20 hours of hypoxia and after LHTL. These results confirm that altitude decreases BRS but the decrease is similar between HH and NH. The persistence of this decrease after the cessation of a chronic exposure is new and does not differ between HH and NH. The previously reported physiological differences between NH and HH do not appear strong enough to induce different BRS responses.
... In this context, serum EPO measurement may also have been beneficial. Nonetheless, the LHTL protocol employed in the present study is a popular training protocol amongst athletes and remains practically relevant In addition, whilst the Hbmass response evoked by hypobaric hypoxia is expected to be similar to a matched dose of normobaric hypoxia (40); future research should investigate the responses of ERFE and hepcidin during both simulated-and naturalaltitude training camps. ...
The integrity of Athlete Biological Passport (ABP) is underpinned by understanding normal fluctuations of its biomarkers to environmental or medical conditions, e.g. altitude training or iron deficiency. The combined impact of altitude and iron supplementation on the ABP was evaluated in endurance-trained athletes (n=34) undertaking 3-weeks of simulated live-high: train-low (14 h.d-1, 3000m). Athletes received either oral, intravenous (IV) or placebo iron supplementation, commencing two weeks prior and continuing throughout hypoxic exposure. Venous blood was sampled twice prior, weekly during, and up to 6-weeks after altitude. Individual ABP thresholds for haemoglobin concentration ([Hb]), reticulocyte percentage (%retic), and OFF score were calculated using the adaptive model and assessed at 99% and 99.9% specificity. Eleven athletes returned values outside of the calculated reference ranges at 99%, with 8 at 99.9%. The percentage of athletes exceeding the thresholds in each group was similar, but IV returned the most individual occurrences. A similar frequency of abnormalities occurred across the three biomarkers, with abnormal [Hb] and OFF score values arising mainly during-, and %retic values mainly post- altitude. Removing samples collected during altitude from the model resulted in ten athletes returning abnormal values at 99% specificity, two of whom had not triggered the model previously. In summary, the abnormalities observed in response to iron supplementation and hypoxia were not systematic and mostly in line with expected physiological adaptations. They do not represent a uniform weakness in the ABP. Nevertheless, altitude training and iron supplementation should be carefully considered by experts evaluating abnormal ABP profiles.
Purpose
Elite swimmers often schedule altitude training camps ahead of major events in an attempt to maximize performance. However, the relationships between altitude-induced hematological changes, markers of training adaptation, and performance changes in such context are unclear. This study assessed hematological status, markers of daily adaptation, and swimming performance in elite middle-distance and distance swimmers during a 22-day altitude training camp at 2,320 m, 2 weeks prior to World Championship qualification competition.
Methods
Venous blood was obtained and total hemoglobin mass (tHbmass) measured (CO rebreathing) in 7 elite swimmers (4 females, 3 males) 8 days before and on day 22 of the altitude camp. Resting heart rate, peripheral oxygen saturation, urinary specific gravity, body mass, fatigue and self-reported sleep duration and quality were monitored daily during the altitude camp. Swimming performance was assessed through a standardized set (6 sets of 4 maximal repetitions of 100 m front crawl) on days 3, 10 and 17 of the camp, and at sea level competitions (200 m–1,500 m) immediately after the camp, and 2 weeks later.
Results
tHbmass (+5.6 ± 3.3%; range: 2.1%–11.0%; p < 0.05), red blood cell count, hemoglobin concentration, hematocrit increased at the end of the training camp (p < 0.05). Performance at altitude improved throughout the camp (+1.4 ± 0.4%; range: 0.7%–2.5%; p < 0.05). No significant relationship was noted between hematological changes, the change in altitude performance and any of the monitored daily markers of adaptation during the camp. Compared to the swimmers’ previous personal best, competition performances did not improve immediately (2.5% ± 1.9% slower times) and 2 weeks after altitude (1.2% ± 1.4% slower times).
Conclusion
The 22-day altitude training camp at 2,320 m was beneficial for elite swimmers’ tHbmass, hematological status and performance at altitude, but these benefits did not clearly translate into enhanced sea level performance immediately after or 2 weeks later. The present study confirms the large inter-individual variability in hematological responses to altitude training, and that the improvement in performance at altitude and sea level may depend on factors other than the increase in tHbmass alone.
Occupational pulmonary diseases (OPDs) pose a significant global health challenge, contributing to high mortality rates. This review delves into the pathophysiology of hypoxia and the safety of intermittent hypoxic conditioning (IHC) in OPD patients. By examining sources such as PubMed, Relemed, NLM, Scopus, and Google Scholar, the review evaluates the efficacy of IHC in clinical outcomes for OPD patients. It highlights the complexities of cardiovascular and respiratory regulation dysfunctions in OPDs, focusing on respiratory control abnormalities and the impact of intermittent hypoxic exposures. Key areas include the physiological effects of hypoxia, the role of hypoxia-inducible factor-1 alpha (HIF-1α) in occupational lung diseases, and the links between brain ischemia, stroke, and OPDs. The review also explores the interaction between intermittent hypoxic exposures, mitochondrial energetics, and lung physiology. The potential of IHE to improve clinical manifestations and underlying pathophysiology in OPD patients is thoroughly examined. This comprehensive analysis aims to benefit molecular pathologists, pulmonologists, clinicians, and physicians by enhancing understanding of IHE's clinical benefits, from research to patient care, and improving clinical outcomes for OPD patients.
Athletes use hypoxic living and training to increase hemoglobin mass (Hb mass ), but Hb mass declines rapidly upon return to sea level. We investigated whether Intermittent Hypoxic Exposure (IHE) + Continuous Hypoxic Training (CHT) after return to sea level maintained elevated Hb mass , and if changes in Hb mass were transferred to changes in maximal oxygen uptake (V̇O 2max ) and exercise performance. Hb mass was measured in 58 endurance athletes before (PRE), after (POST1), and 30 days after (POST2) a 27 ± 4-day training camp in hypoxia (n=44, HYP) or at sea level (n=14, SL). After return to sea level, 22 athletes included IHE (2 h rest) + CHT (1 h training) into their training every third day for one month (HYP IHE+ CHT ), whereas the other 22 HYP athletes were not exposed to IHE or CHT (HYP SL ). Hb mass increased from PRE to POST1 in both HYP IHE+CHT (4.4 ± 0.7%, mean ± SEM) and HYP SL (4.1 ± 0.6%) (both p<0.001). Compared to PRE, Hb mass at POST2 remained 4.2 ± 0.8% higher in HYP IHE+CHT (p<0.001) and 1.9 ± 0.5% higher in HYP SL (p=0.023), indicating a significant difference between the groups (p=0.002). In SL, no significant changes were observed in Hb mass with mean alterations between -0.5% and 0.4%. V̇O 2max and time to exhaustion during an incremental treadmill test (n=35) were elevated from PRE to POST2 only in HYP IHE+ CHT (5.8 ± 1.2% and 5.4 ± 1.4%, respectively, both p<0.001). IHE+CHT possesses the potential to mitigate the typical decline in Hb mass commonly observed during the initial weeks after return to sea level.
Introduction
Elite breath-hold divers (BHD) enduring apneas of more than 5 min are characterized by tolerance to arterial blood oxygen levels of 4.3 kPa and low oxygen-consumption in their hearts and skeletal muscles, similar to adult seals. Adult seals possess an adaptive higher hemoglobin-concentration and Bohr effect than pups, and when sedated, adult seals demonstrate a blood shift from the spleen towards the brain, lungs, and heart during apnea. We hypothesized these observations to be similar in human BHD. Therefore, we measured hemoglobin- and 2,3-biphosphoglycerate-concentrations in BHD (n = 11) and matched controls (n = 11) at rest, while myocardial mass, spleen and lower extremity volumes were assessed at rest and during apnea in BHD.
Methods and results
After 4 min of apnea, left ventricular myocardial mass (LVMM) determined by ¹⁵O-H2O-PET/CT (n = 6) and cardiac MRI (n = 6), was unaltered compared to rest. During maximum apnea (∼6 min), lower extremity volume assessed by DXA-scan revealed a ∼268 mL decrease, and spleen volume, assessed by ultrasonography, decreased ∼102 mL. Compared to age, BMI and VO2max matched controls (n = 11), BHD had similar spleen sizes and 2,3- biphosphoglycerate-concentrations, but higher total hemoglobin-concentrations.
Conclusion
Our results indicate: 1) Apnea training in BHD may increase hemoglobin concentration as an oxygen conserving adaptation similar to adult diving mammals. 2) The blood shift during dry apnea in BHD is 162% more from the lower extremities than from the spleen. 3) In contrast to the previous theory of the blood shift demonstrated in sedated adult seals, blood shift is not towards the heart during dry apnea in humans.
Acclima(tiza)tion to heat or hypoxia enhances work capacity in hot and hypoxic environmental conditions, respectively; an acclimation response considered to be mediated by stimuli-specific molecular/systemic adaptations and potentially facilitated by the addition of exercise sessions. Promising findings at the cellular level provided the impetus for recent studies investigating whether acclimation to one stressor will ultimately facilitate whole body performance when exercise is undertaken in a different environmental condition. The present critical mini-review examines the theory of cross-adaptation between heat and hypoxia with particular reference to the determinants of aerobic performance. Indeed, early functional adaptations (improved exercise economy, enhanced oxyhemoglobin saturation) succeeded by later morphological adaptations (increased hemoglobin mass) might aid acclimatized humans perform aerobic work in an alternative environmental setting. Longer-term acclimation protocols that focus on the specific adaptation kinetics (and further allow for the adaptation reversal) will elucidate the exact physiological mechanisms that might mediate gains in aerobic performance or explain the lack thereof.
Professional athletes often have to participate in competitions in climatic conditions that differ from the optimal or habitual ones for their place of residence. In this regard, it seems relevant to the question of how borderline and extreme external conditions (low and high ambient temperatures, changes in atmospheric pressure, altitude) affect sports performance and endurance. The review presents the biochemical mechanisms underlying the adaptation of athletes to environmental conditions. The human body maintains a fairly constant internal temperature (in some articles — the core) of the body at a level of 37 ± 10C throughout its life, despite a wide range of environmental parameters. The intensity of the processes providing for the release of heat is reflexively regulated. The neurons responsible for heat exchange are located in the center of thermoregulation of the hypothalamus. In the course of evolution, mammals have developed a variety of mechanisms for regulating body temperature, including nervous and humoral, that affect energy metabolism and behavioral responses. There are two ways of heat generation: contractile thermogenesis, due to contractions of skeletal muscles (a special case — cold muscle tremors), and non-contractile — when the processes of cellular metabolism are activated: lipolysis (in particular, brown adipose tissue) and glycolysis. When exposed to extreme ambient temperatures, the thermoregulatory system adjusts to maintain a stable core body temperature by preventing heat loss and increasing heat production in cold conditions, or increasing heat dissipation if the ambient temperature rises. The ambient temperature corresponding to 20–25 ºС on land and 30–35 ºС in water is considered thermoneutral for humans in a state of relative rest. However, any deviations from these conditions, especially against the background of intense physical exercise, can lead to functional overstrain, decreased endurance and sports performance.
Oxygen delivery to the retinal pigment epithelium and the outer retina is essential for metabolism, function, and survival of photoreceptors. Chronically reduced oxygen supply leads to retinal pathologies in patients and causes age-dependent retinal degeneration in mice. Hypoxia can result from decreased levels of inspired oxygen (normobaric hypoxia) or reduced barometric pressure (hypobaric hypoxia). Since the response of retinal cells to chronic normobaric or hypobaric hypoxia is mostly unknown, we examined the effect of six hypoxic conditions on the retinal transcriptome and photoreceptor morphology. Mice were exposed to short- and long-term normobaric hypoxia at 400 m or hypobaric hypoxia at 3450 m above sea level. Longitudinal studies over 11 weeks in normobaric hypoxia revealed four classes of genes that adapted differentially to the hypoxic condition. Seventeen genes were specifically regulated in hypobaric hypoxia and may affect the structural integrity of the retina, resulting in the shortening of photoreceptor segment length detected in various hypoxic groups. This study shows that retinal cells have the capacity to adapt to long-term hypoxia and that consequences of hypobaric hypoxia differ from those of normobaric hypoxia. Our datasets can be used as references to validate and compare retinal disease models associated with hypoxia.
We recently measured the development of hemoglobin mass (Hbmass) in 10 Swiss national team endurance athletes between ages 16–19. Level of Hbmass at age 16 was an important predictor for Hbmass and endurance performance at age 19. The aim was to determine how many of these young athletes were still members of Swiss national teams (NT) at age 25, how many already terminated their career (TC), and whether Hbmass at ages 16 and 19 was different between the NT and TC group. We measured Hbmass using the optimized carbon monoxide re-breathing technique in 10 high-performing endurance athletes every 0.5 years beginning at age 16 and ending at age 19. At age 25, two athletes were in the NT group and eight athletes in the TC group. Mean absolute, body weight-, and lean body mass (LBM) related Hbmass at age 16 was 833 ± 61 g, 13.7 ± 0.2 g/kg and 14.2 ± 0.2 g/kg LBM in the NT group and 742 ± 83 g, 12.2 ± 0.7 g/kg and 12.8 ± 0.8 g/kg LBM in the TC group. At age 19, Hbmass was 1,042 ± 89 g, 14.6 ± 0.2 g/kg and 15.4 ± 0.2 g/kg LBM in the NT group and 863 ± 109 g, 12.7 ± 1.1 g/kg and 13.5 ± 1.1 g/kg LBM in the TC group. Body weight- and LBM related Hbmass were higher in the NT group than in the TC group at ages 16 and 19 (p < 0.05). These results indicate, that Hbmass at ages 16 and 19 possibly could be an important predictor for later national team membership in endurance disciplines.
Purpose The purpose of this study is to emphasize the need for the establish and the use of altitude training center via examining exercise training method in natural or artificial altitude environment that is applied to various elite athletes in various advanced countries to maximize exercise performance and its effectiveness. Results Altitude training in natural or artificial altitude environment enhances aerobic and anaerobic exercise performance baesd on the hematological and nonhematological adaptations to hypoxic conditions. These altitude training methods can be classified into living high training high (LHTH), living high training low (LHTL), and living low training high (LLTH). LHTH (i.e., developed since the 1968 Mexico Olympics) and LHTL (i.e., developed in the 1990s by Levine and Stray-Gundersen) improve exercise performance via hematologic changes through erythropoiesis such as increased hemoglobin mass and erythrocyte volume. On the other hand, LLTH (i.e., has been developed variously since the 2000s) is composed continuous hypoxic training (CHT), intermittent hypoxic training (IHT) and repeated sprint training in hypoxia (RSH), and the altitude environment is constructed using a vacuum pump and a nitrogen generator. In general, LLTH method dose not induce hematological change in a short time within 3 hours. However, CHT and IHT enhance aerobic exercise capacity by improved exercise economy, supply and utilization of blood to tissues, capillary and mitochondrial densities, and oxidative enzyme activity through various biochemical and structural changes in skeletal muscle and cardiac muscle. RSH enhances anaerobic power and repetitive sprint performance by improving glycolytic enzyme, glucose transport, and pH control. In Korea, however, there are almost no facilities for altitude training that is applied to enhance athletic performance in advanced sports countries and recognition of the need for altitude training is also very poor. Conclusions Therefore, it is very urgent to develop altitude training for maximizing athletic performance in Korea and a lot of support and efforts are needed from the government and local governments.
At the Olympic level, differences in performance are typically less than 0.5%. This helps explain why many contemporary elite endurance athletes in summer and winter sport incorporate some form of altitude/hypoxic training within their year-round training plan, believing that it will provide the "competitive edge" to succeed at the Olympic level. The purpose of this paper is to describe the practical application of altitude/hypoxic training as utilized by elite athletes. Within the general framework of the paper, both anecdotal and scientific evidence will be presented relative to the efficacy of several contemporary altitude/hypoxic training models and devices currently used by Olympic-level athletes for the purpose of legally enhancing performance. These include the three primary altitude/hypoxic training models: 1) live high + train high (LH + TH), 2) live high + train low (LH + TL), and 3) live low + train high (LL + TH). The LH + TL model will be examined in detail and will include its various modifications: natural/terrestrial altitude, simulated altitude via nitrogen dilution or oxygen filtration, and normobaric normoxia via supplemental oxygen. A somewhat opposite approach to LH + TL is the altitude/hypoxic training strategy of LL + TH, and data regarding its efficacy will be presented. Recently, several of these altitude/hypoxic training strategies and devices underwent critical review by the World Anti-Doping Agency (WADA) for the purpose of potentially banning them as illegal performance-enhancing substances/methods. This paper will conclude with an update on the most recent statement from WADA regarding the use of simulated altitude devices.
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 []). 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 (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 for RSH versus RSN was not significantly different.
Purpose: We investigated the changes in physiological and performance parameters after a Live High-Train Low (LHTL) altitude camp in normobaric (NH) or hypobaric hypoxia (HH) to reproduce the actual training practices of endurance athletes using a crossover-designed study.
Methods: Well-trained triathletes (n = 16) were split into two groups and completed two 18-day LTHL camps during which they trained at 1100–1200 m and lived at 2250 m (PiO2 = 111.9 ± 0.6 vs. 111.6 ± 0.6 mmHg) under NH (hypoxic chamber; FiO2 18.05 ± 0.03%) or HH (real altitude; barometric pressure 580.2 ± 2.9 mmHg) conditions. The subjects completed the NH and HH camps with a 1-year washout period. Measurements and protocol were identical for both phases of the crossover study. Oxygen saturation (SpO2) was constantly recorded nightly. PiO2 and training loads were matched daily. Blood samples and VO2max were measured before (Pre-) and 1 day after (Post-1) LHTL. A 3-km running-test was performed near sea level before and 1, 7, and 21 days after training camps.
Results: Total hypoxic exposure was lower for NH than for HH during LHTL (230 vs. 310 h; P < 0.001). Nocturnal SpO2 was higher in NH than in HH (92.4 ± 1.2 vs. 91.3 ± 1.0%, P < 0.001). VO2max increased to the same extent for NH and HH (4.9 ± 5.6 vs. 3.2 ± 5.1%). No difference was found in hematological parameters. The 3-km run time was significantly faster in both conditions 21 days after LHTL (4.5 ± 5.0 vs. 6.2 ± 6.4% for NH and HH), and no difference between conditions was found at any time.
Conclusion: Increases in VO2max and performance enhancement were similar between NH and HH conditions.
Objectives:
To determine the efficacy of live-high train-low on team-sport athlete physical capacity and the time-course for adaptation.
Design:
Pre-post parallel-groups.
Methods:
Fifteen Australian footballers were matched for Yo-Yo Intermittent recovery test level 2 (Yo-YoIR2) performance and assigned to LHTL (n=7) or control (Con; n=8). LHTL spent 19 nights (3×5 nights, 1×4 nights, each block separated by 2 nights at sea level) at 3000-m simulated altitude (FIO2: 0.142). Yo-Yo IR2 was performed pre and post 5, 15, and 19 nights. A 2- and 1-km time-trial (TT) was performed pre and post intervention. Haemoglobin mass (Hbmass) was measured in LHTL after 5, 10, 15, and 19 nights. A contemporary statistical approach using effect size, confidence limits, and magnitude-based inferences was used to measure changes between groups.
Results:
Compared to pre, Hbmass was possibly higher after 15 (3.8%, effect size (ES) 0.19, 90% confidence limits 0.05-0.33) and very likely higher after 19 nights (6.7%, 0.35, 0.10; 0.52). For Yo-Yo IR2, LHTL group change was not meaningfully different to Con after 5 nights, possibly greater after 15 (10.2%, 0.37, -0.29; 1.04), and likely greater after 19 nights (13.5%, 0.49, -0.16; 1.14). Both groups improved 2-km TT, with LHTL improvement possibly higher than CON (1.9%, 0.22, -0.18; 0.62). Only LHTL improved 1-km TT, with LHTL improvement likely greater than CON (4.6%, 0.56, -0.08; 1.04).
Conclusions:
Fifteen nights of LHTL was possibly effective, while 19 nights was effective at increasing Hbmass, Yo-Yo IR2 and repeated TT performance more than sea-level training.
Objective
To characterise the time course of changes in haemoglobin mass (Hbmass) in response to altitude exposure.
Methods
This meta-analysis uses raw data from 17 studies that used carbon monoxide rebreathing to determine Hbmass prealtitude, during altitude and postaltitude. Seven studies were classic altitude training, eight were live high train low (LHTL) and two mixed classic and LHTL. Separate linear-mixed models were fitted to the data from the 17 studies and the resultant estimates of the effects of altitude used in a random effects meta-analysis to obtain an overall estimate of the effect of altitude, with separate analyses during altitude and postaltitude. In addition, within-subject differences from the prealtitude phase for altitude participant and all the data on control participants were used to estimate the analytical SD. The ‘true’ between-subject response to altitude was estimated from the within-subject differences on altitude participants, between the prealtitude and during-altitude phases, together with the estimated analytical SD.
Results
During-altitude Hbmass was estimated to increase by ∼1.1%/100 h for LHTL and classic altitude. Postaltitude Hbmass was estimated to be 3.3% higher than prealtitude values for up to 20 days. The within-subject SD was constant at ∼2% for up to 7 days between observations, indicative of analytical error. A 95% prediction interval for the ‘true’ response of an athlete exposed to 300 h of altitude was estimated to be 1.1–6%.
Conclusions
Camps as short as 2 weeks of classic and LHTL altitude will quite likely increase Hbmass and most athletes can expect benefit.
Much hypoxia research has been carried out at high altitude in a hypobaric hypoxia (HH) environment. Many research teams seek to replicate high-altitude conditions at lower altitudes in either hypobaric hypoxic conditions or normobaric hypoxic (NH) laboratories. Implicit in this approach is the assumption that the only relevant condition that differs between these settings is the partial pressure of oxygen (PO2), which is commonly presumed to be the principal physiological stimulus to adaptation at high altitude. This systematic review is the first to present an overview of the current available literature regarding crossover studies relating to the different effects of HH and NH on human physiology. After applying our inclusion and exclusion criteria, 13 studies were deemed eligible for inclusion. Several studies reported a number of variables (e.g. minute ventilation and NO levels) that were different between the two conditions, lending support to the notion that true physiological difference is indeed present. However, the presence of confounding factors such as time spent in hypoxia, temperature, and humidity, and the limited statistical power due to small sample sizes, limit the conclusions that can be drawn from these findings. Standardisation of the study methods and reporting may aid interpretation of future studies and thereby improve the quality of data in this area. This is important to improve the quality of data that is used for improving the understanding of hypoxia tolerance, both at altitude and in the clinical setting.
Objectives
Water polo requires high aerobic power to meet the demands of match play. Live high:train low (LHTL) may enhance aerobic capacity at sea level. Before the Olympics, the Australian women's water polo team utilised LHTL in an attempt to enhance aerobic fitness.
Methods
Over 6 months, 11 players completed three normobaric LHTL exposures (block 1:11 days at 3000 m; block 2+3:9 days at 2500 m, 11 days normoxia, 10 days at 2800 m). Haemoglobin mass (Hbmass) was measured through carbon monoxide-rebreathing. Before each block, the relationship between Hbmass and water polo-specific aerobic fitness was investigated using the Multistage Shuttle Swim Test (MSST). Effect size statistics were adopted with likely, highly likely and almost certainly results being >75%, >95%, >99%, respectively. A Pearson product moment correlation was used to characterise the association between pooled data of Hbmass and MSST.
Results
Hbmass (mean±SD, pre 721±66 g) likely increased after block 1 and almost certainly after block 2+3 (% change; 90% confidence limits: block 1: 3.7%; 1.3–6.2%, block 2+3: 4.5%; 3.8–5.1%) and the net effect was almost certainly higher after block 2+3 than before block 1 (pre) by 8.5%; 7.3–9.7%. There was a very large correlation between Hbmass (g/kg) and MSST score (r=0.73).
Conclusions
LHTL exposures of <2 weeks induced approximately 4% increase in Hbmass of water polo players. Extra Hbmass may increase aerobic power, but since match performance is nuanced by many factors it is impossible to ascertain whether the increased Hbmass contributed to Australia's Bronze medal.
We investigated the changes in both performance and selected physiological parameters following a Live High-Train Low (LHTL) altitude camp in either normobaric hypoxia (NH) or hypobaric hypoxia (HH) replicating current "real" practices of endurance athletes. Well-trained triathletes were split into two groups (NH, n = 14 and HH, n = 13) and completed an 18-d LHTL camp during which they trained at 1100-1200 m and resided at an altitude of 2250 m (PiO2 = 121.7+/-1.2 vs. 121.4+/-0.9 mmHg) under either NH (hypoxic chamber; FiO2 15.8+/-0.8%) or HH (real altitude; barometric pressure 580+/-23 mmHg) conditions. Oxygen saturations (SpO2) were recorded continuously daily overnight. PiO2 and training loads were matched daily. Before (Pre-) and 1 day after (Post-) LHTL, blood samples, VO2max, and total haemoglobin mass (Hbmass) were measured. A 3-km running test was performed near sea level twice before, and 1, 7, and 21 days following LHTL. During LHTL, hypoxic exposure was lower for the NH group than for the HH group (220 vs. 300 h; P<0.001). Night SpO2 was higher (92.1+/-0.3 vs. 90.9+/-0.3%, P<0.001), and breathing frequency was lower in the NH group compared with the HH group (13.9+/-2.1 vs. 15.5+/-1.5 breath.min-1, P<0.05). Immediately following LHTL, similar increases in VO2max (6.1+/-6.8 vs. 5.2+/-4.8%) and Hbmass (2.6+/-1.9 vs. 3.4+/-2.1%) were observed in NH and HH groups, respectively, while 3-km performance was not improved. However, 21 days following the LHTL intervention, 3-km run time was significantly faster in the HH (3.3+/-3.6%; P<0.05) versus the NH (1.2+/-2.9%; ns) group. In conclusion, the greater degree of race performance enhancement by day 21 after an 18-d LHTL camp in the HH group was likely induced by a larger hypoxic dose. However, one cannot rule out other factors including differences in sleeping desaturations and breathing patterns, thus suggesting higher hypoxic stimuli in the HH group.
Aim
To quantify the year-to-year variability of altitude-induced changes in haemoglobin mass (Hbmass) in elite team-sport athletes.
Methods
12 Australian-Footballers completed a 19-day (ALT1) and 18-day (ALT2) moderate altitude (∼2100 m), training camp separated by 12 months. An additional 20 participants completed only one of the two training camps (ALT1 additional n=9, ALT2 additional n=11). Total Hbmass was assessed using carbon monoxide rebreathing before (PRE), after (POST1) and 4 weeks after each camp. The typical error of Hbmass for the pooled data of all 32 participants was 2.6%. A contemporary statistics analysis was used with the smallest worthwhile change set to 2% for Hbmass.
Results
POST1 Hbmass was very likely increased in ALT1 (3.6±1.6%, n=19; mean±∼90 CL) as well as ALT2 (4.4±1.3%, n=23) with an individual responsiveness of 1.3% and 2.2%, respectively. There was a small correlation between ALT1 and ALT2 (R=0.21, p=0.59) for a change in Hbmass, but a moderately inverse relationship between the change in Hbmass and initial relative Hbmass (g/kg (R=−0.51, p=0.04)).
Conclusions
Two preseason moderate altitude camps 1 year apart yielded a similar (4%) mean increase in Hbmass of elite footballers, with an individual responsiveness of approximately half the group mean effect, indicating that most players gained benefit. Nevertheless, the same individuals generally did not change their Hbmass consistently from year to year. Thus, a ‘responder’ or ‘non-responder’ to altitude for Hbmass does not appear to be a fixed trait.
Background/aims:
The week's cycle influences sleep, exercise, and eating habits. An accurate description of weekly weight rhythms has not been reported yet - especially across people who lose weight versus those who maintain or gain weight.
Methods:
The daily weight in 80 adults (BMI 20.0-33.5 kg/m(2); age, 25-62 years) was recorded and analysed to determine if a group-level weekly weight fluctuation exists. This was a retrospective study of 4,657 measurements during 15-330 monitoring days. Semi-parametric regression was used to model the rhythm.
Results:
A pattern of daily weight changes was found (p < 0.05), with higher weight early in the week (Sunday and Monday) and decreasing weight during the week. Increases begin on Saturday and decreases begin on Tuesday. This compensation pattern was strongest for those who lost or maintained weight and weakest for those who slowly gained weight.
Conclusion:
Weight variations between weekends and weekdays should be considered as normal instead of signs of weight gain. Those who compensate the most are most likely to either lose or maintain weight over time. Long-term habits may make more of a difference than short-term splurges. People prone to weight gain could be counselled about the importance of weekday compensation.
Despite the limited research on the effects of altitude (or hypoxic) training interventions on team-sport performance, players from all around the world engaged in these sports are now using altitude training more than ever before. In March 2013, an Altitude Training and Team Sports conference was held in Doha, Qatar, to establish a forum of research and practical insights into this rapidly growing field. A round-table meeting in which the panellists engaged in focused discussions concluded this conference. This has resulted in the present position statement, designed to highlight some key issues raised during the debates and to integrate the ideas into a shared conceptual framework. The present signposting document has been developed for use by support teams (coaches, performance scientists, physicians, strength and conditioning staff) and other professionals who have an interest in the practical application of altitude training for team sports. After more than four decades of research, there is still no consensus on the optimal strategies to elicit the best results from altitude training in a team-sport population. However, there are some recommended strategies discussed in this position statement to adopt for improving the acclimatisation process when training/ competing at altitude and for potentially enhancing sea-level performance. It is our hope that this information will be intriguing, balanced and, more importantly, stimulating to the point that it promotes constructive discussion and serves as a guide for future research aimed at advancing the bourgeoning body of knowledge in the area of altitude training for team sports.
Objectives
The optimal strategy for soccer teams playing at altitude is not known, that is, ‘fly-in, fly-out’ versus short-term acclimatisation. Here, we document changes in blood gas and vascular volumes of sea-level (Australian, n=20) and altitude (Bolivian, n=19) native soccer players at 3600 m.
Methods
Haemoglobin-oxygen saturation (Hb-sO2), arterial oxygen content (CaO2), haemoglobin mass (Hbmass), blood volume (BV) and blood gas concentrations were measured before descent (Bolivians only), together with aerobic fitness (via Yo-YoIR1), near sea-level, after ascent and during 13 days at 3600 m.
Results
At baseline, haemoglobin concentration [Hb] and Hbmass were higher in Bolivians (mean±SD; 18.2±1.0 g/dL, 12.8±0.8 g/kg) than Australians (15.0±0.9 g/dL, 11.6±0.7 g/kg; both p≤0.001). Near sea-level, [Hb] of Bolivians decreased to 16.6±0.9 g/dL, but normalised upon return to 3600 m; Hbmass was constant regardless of altitude. In Australians, [Hb] increased after 12 days at 3600 m to 17.3±1.0 g/dL; Hbmass increased by 3.0±2.7% (p≤0.01). BV decreased in both teams at altitude by ∼400 mL. Arterial partial pressure for oxygen (PaO2), Hb-sO2 and CaO2 of both teams decreased within 2 h of arrival at 3600 m (p≤0.001) but increased over the following days, with CaO2 overcompensated in Australians (+1.7±1.2 mL/100 mL; p≤0.001). Yo-YoIR1 was lower on the 3rd versus 10th day at altitude and was significantly related to CaO2.
Conclusions
The marked drop in PaO2 and CaO2 observed after ascent does not support the ‘fly-in, fly-out’ approach for soccer teams to play immediately after arrival at altitude. Although short-term acclimatisation was sufficient for Australians to stabilise their CaO2 (mostly due to loss of plasma volume), 12 days appears insufficient to reach chronic levels of adaption.
Purpose
To quantify the changes of hemoglobin mass (Hb mass ) and maximum oxygen consumption (VO 2max ) after 22 days training at 1300–1800 m combined with nightly exposure to 3000-m simulated altitude. We hypothesized that with simulated 3000-m altitude, an adequate beneficial dose could be as little as 10 h/24 h.
Methods
Fourteen male collegiate runners were equally divided into 2 groups: altitude (ALT) and control (CON). Both groups spent 22 days at 1300–1800 m. ALT spent 10 h/night for 21 nights in simulated altitude (3000 m), and CON stayed at 1300 m. VO 2max and Hb mass were measured twice before and once after the intervention. Blood was collected for assessment of percent reticulocytes (%retics), serum erythropoietin (EPO), ferritin, and soluble transferrin receptor (sTfR) concentrations.
Results
Compared with CON there was an almost certain increase in absolute VO 2max (8.6%, 90% confidence interval 4.8–12.6%) and a likely increase in absolute Hb mass (3.5%; 0.9–6.2%) at postintervention. The %retics were at least very likely higher in ALT than in CON throughout the 21 nights, and sTfR was also very likely higher in the ALT group until day 17. EPO of ALT was likely higher than that of CON on days 1 and 5 at altitude, whereas serum ferritin was likely lower in ALT than CON for most of the intervention.
Conclusions
Together the combination of the natural and simulated altitude was a sufficient total dose of hypoxia to increase both Hb mass and VO 2max .
Cejuela-Anta R, Esteve-Lanao J. Training load quantification in triathlon. J. Hum. Sport Exerc. Vol. 6, No. 2, pp. 218-232, 2011. There are different Indices of Training Stress of varying complexity, to quantification Training load. Examples include the training impulse (TRIMP), the session (RPE), Lucia¿s TRIMP or Summated Zone Score. But the triathlon, a sport to be combined where there are interactions between different segments, is a complication when it comes to quantify the training. The aim of this paper is to review current methods of quantification, and to propose a scale to quantify the training load in triathlon simple application.
Aim of the study was to determine the influence of classic altitude training on hemoglobin mass (Hb-mass) in elite swimmers under the following aspects: (1) normal oscillation of Hb-mass at sea level; (2) time course of adaptation and de-adaptation; (3) sex influences; (4) influences of illness and injury; (5) interaction of Hb-mass and competition performance. Hb-mass of 45 top swimmers (male 24; female 21) was repeatedly measured (~6 times) over the course of 2 years using the optimized CO-rebreathing method. Twenty-five athletes trained between one and three times for 3-4 weeks at altitude training camps (ATCs) at 2,320 m (3 ATCs) and 1,360 m (1 ATC). Performance was determined by analyzing 726 competitions according to the German point system. The variation of Hb-mass without hypoxic influence was 3.0 % (m) and 2.7 % (f). At altitude, Hb-mass increased by 7.2 ± 3.3 % (p < 0.001; 2,320 m) and by 3.8 ± 3.4 % (p < 0.05; 1,360 m). The response at 2,320 m was not sex-related, and no increase was found in ill and injured athletes (n = 8). Hb-mass was found increased on day 13 and was still elevated 24 days after return (4.0 ± 2.7 %, p < 0.05). Hb-mass had only a small positive effect on swimming performance; an increase in performance was only observed 25-35 days after return from altitude. In conclusion, the altitude (2,320 m) effect on Hb-mass is still present 3 weeks after return, it decisively depends on the health status, but is not influenced by sex. In healthy subjects it exceeds by far the oscillation occurring at sea level. After return from altitude performance increases after a delay of 3 weeks.
The general practice of altitude training is widely accepted as a means to enhance sport performance despite a lack of rigorous scientific studies. For example, the scientific gold-standard design of a double-blind, placebo-controlled, cross-over trial has never been conducted on altitude training. Given that few studies have utilised appropriate controls, there should be more scepticism concerning the effects of altitude training methodologies. In this brief review we aim to point out weaknesses in theories and methodologies of the various altitude training paradigms and to highlight the few well-designed studies to give athletes, coaches and sports medicine professionals the current scientific state of knowledge on common forms of altitude training. Another aim is to encourage investigators to design well-controlled studies that will enhance our understanding of the mechanisms and potential benefits of altitude training.
We compared changes in performance and total haemoglobin mass (tHb) of elite swimmers in the weeks following either Classic or Live High:Train Low (LHTL) altitude training. Twenty-six elite swimmers (15 male, 11 female, 21.4 ± 2.7 years; mean ± SD) were divided into two groups for 3 weeks of either Classic or LHTL altitude training. Swimming performances over 100 or 200 m were assessed before altitude, then 1, 7, 14 and 28 days after returning to sea-level. Total haemoglobin mass was measured twice before altitude, then 1 and 14 days after return to sea-level. Changes in swimming performance in the first week after Classic and LHTL were compared against those of Race Control (n = 11), a group of elite swimmers who did not complete altitude training. In addition, a season-long comparison of swimming performance between altitude and non-altitude groups was undertaken to compare the progression of performances over the course of a competitive season. Regardless of altitude training modality, swimming performances were substantially slower 1 day (Classic 1.4 ± 1.3% and LHTL 1.6 ± 1.6%; mean ± 90% confidence limits) and 7 days (0.9 ± 1.0% and 1.9 ± 1.1%) after altitude compared to Race Control. In both groups, performances 14 and 28 days after altitude were not different from pre-altitude. The season-long comparison indicated that no clear advantage was obtained by swimmers who completed altitude training. Both Classic and LHTL elicited ~4% increases in tHb. Although altitude training induced erythropoeisis, this physiological adaptation did not transfer directly into improved competitive performance in elite swimmers.
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.
Human endurance performance can be predicted from maximal oxygen consumption (Vo(2max)), lactate threshold, and exercise efficiency. These physiological parameters, however, are not wholly exclusive from one another, and their interplay is complex. Accordingly, we sought to identify more specific measurements explaining the range of performance among athletes. Out of 150 separate variables we identified 10 principal factors responsible for hematological, cardiovascular, respiratory, musculoskeletal, and neurological variation in 16 highly trained cyclists. These principal factors were then correlated with a 26-km time trial and test of maximal incremental power output. Average power output during the 26-km time trial was attributed to, in order of importance, oxidative phosphorylation capacity of the vastus lateralis muscle (P = 0.0005), steady-state submaximal blood lactate concentrations (P = 0.0017), and maximal leg oxygenation (sO(2LEG)) (P = 0.0295), accounting for 78% of the variation in time trial performance. Variability in maximal power output, on the other hand, was attributed to total body hemoglobin mass (Hb(mass); P = 0.0038), Vo(2max) (P = 0.0213), and sO(2LEG) (P = 0.0463). In conclusion, 1) skeletal muscle oxidative capacity is the primary predictor of time trial performance in highly trained cyclists; 2) the strongest predictor for maximal incremental power output is Hb(mass); and 3) overall exercise performance (time trial performance + maximal incremental power output) correlates most strongly to measures regarding the capability for oxygen transport, high Vo(2max) and Hb(mass), in addition to measures of oxygen utilization, maximal oxidative phosphorylation, and electron transport system capacities in the skeletal muscle.
New methods and devices for pursuing performance enhancement through altitude training were developed in Scandinavia and the USA in the early 1990s. At present, several forms of hypoxic training and/or altitude exposure exist: traditional ‘live high-train high’ (LHTH), contemporary ‘live high-train low’ (LHTL), intermittent hypoxic exposure during rest (IHE) and intermittent hypoxic exposure during continuous session (IHT). Although substantial differences exist between these methods of hypoxic training and/ or exposure, all have the same goal: to induce an improvement in athletic performance at sea level. They are also used for preparation for competition at altitude and/or for the acclimatization of mountaineers.
The underlying mechanisms behind the effects of hypoxic training are widely debated. Although the popular view is that altitude training may lead to an increase in haematological capacity, this may not be the main, or the only, factor involved in the improvement of performance. Other central (such as ventilatory, haemodynamic or neural adaptation) or peripheral (such as muscle buffering capacity or economy) factors play an important role.
LHTL was shown to be an efficient method. The optimal altitude for living high has been defined as being 2200–2500 m to provide an optimal erythropoietic effect and up to 3100m for non-haematological parameters. The optimal duration at altitude appears to be 4 weeks for inducing accelerated erythropoiesis whereas <3 weeks (i.e. 18 days) are long enough for beneficial changes in economy, muscle buffering capacity, the hypoxic ventilatory response or Na+/K+-ATPase activity. One critical point is the daily dose of altitude. A natural altitude of 2500 m for 20–22 h/day (in fact, travelling down to the valley only for training) appears sufficient to increase erythropoiesis and improve sea-level performance. ‘Longer is better’ as regards haematological changes since additional benefits have been shown as hypoxic exposure increases beyond 16 h/day. The minimum daily dose for stimulating erythropoiesis seems to be 12 h/day. For non-haematological changes, the implementation of a much shorter duration of exposure seems possible.
Athletes could take advantage of IHT, which seems more beneficial than IHE in performance enhancement. The intensity of hypoxic exercise might play a role on adaptations at the molecular level in skeletal muscle tissue. There is clear evidence that intense exercise at high altitude stimulates to a greater extent muscle adaptations for both aerobic and anaerobic exercises and limits the decrease in power. So although IHT induces no increase in V̇O2max due to the low‘altitude dose’, improvement in athletic performance is likely to happenwith high-intensity exercise (i.e. above the ventilatory threshold) due to an increase in mitochondrial efficiency and pH/lactate regulation. We propose a new combination of hypoxic method (which we suggest naming Living High-Training Low and High, interspersed; LHTLHi) combining LHTL (five nights at 3000 m and two nights at sea level) with training at sea level except for a few (2.3 per week) IHT sessions of supra-threshold training. This review also provides a rationale on how to combine the different hypoxic methods and suggests advances in both their implementation and their periodization during the yearly training programme of athletes competing in endurance, glycolytic or intermittent sports.
The aim of this study was to determine the time course of changes in haemoglobin mass (Hb(mass)) in well-trained cyclists in response to live high:train low (LHTL). Twelve well-trained male cyclists participated in a 3-week LHTL protocol comprising 3,000 m simulated altitude for ~14 h/day. Prior to LHTL duplicate baseline measurements were made of Hb(mass), maximal oxygen consumption (VO(2max)) and serum erythropoietin (sEPO). Hb(mass) was measured weekly during LHTL and twice in the week thereafter. There was a 3.3% increase in Hb(mass) and no change in VO(2max) after LHTL. The mean Hb(mass) increased at a rate of ~1% per week and this was maintained in the week after cessation of LHTL. The sEPO concentration peaked after two nights of LHTL but there was only a trivial correlation (r = 0.04, P = 0.89) between the increase in sEPO and the increase in Hb(mass). Athletes seeking to gain erythropoietic benefits from moderate altitude need to spend >12 h/day in hypoxia.
Adaptation to living or training in hypoxic environments (altitude training) continues to gain interest from sport scientists and endurance athletes. Here we present the first meta-analytic review of the effects on performance and related physiological measures following adaptation to six protocols of natural or artificial hypoxia: live-high train-high (LHTH), live-high train-low (LHTL), artificial LHTL with daily exposure to long (8–18 hours) continuous, brief (1.5–5 hours) continuous or brief (<1.5 hours) intermittent periods of hypoxia, and artificial live-low train-high (LLTH).
The 51 qualifying studies provided 11–33 estimates for effects on power output with each protocol and up to 20 estimates for effects on maximal oxygen uptake (V̇O2max) and other potential mediators. The meta-analytic random-effect models included covariates to adjust for and estimate moderating effects of study characteristics such as altitude level and days of exposure. Poor reporting of inferential statistics limited the weighting factor in the models to sample size. Probabilistic inferences were derived using a smallest worthwhile effect on performance of 1%. Substantial enhancement of maximal endurance power output in controlled studies of subelite athletes was very likely with artificial brief intermittent LHTL (2.6%; 90% confidence limits ±1.2%), likely with LHTL (4.2%; ±2.9%), possible with artificial long continuous LHTL (1.4; ±2.0%), but unclear with LHTH (0.9; ±3.4%), artificial brief continuous LHTL (0.7%; ±2.5%) and LLTH (0.9%; ±2.4%). In elite athletes, enhancement was possible with natural LHTL (4.0%; ±3.7%), but unclear with other protocols. There was evidence that these effects were mediated at least partly by substantial placebo, nocebo and training-camp effects with some protocols. Enhancing protocols by appropriate manipulation of study characteristics produced clear effects with all protocols (3.5–6.8%) in subelite athletes, but only with LHTH (5.2%) and LHTL (4.3%) in elite athletes. For V̇O2max, increases were very likely with LHTH (4.3%; ±2.6%) in subelite athletes, whereas in elite athletes a ‘reduction’ was possible with LHTH (-1.5%; ±2.0%); changes with other protocols were unclear. Effects on erythropoietic and other physiological mediators provided little additional insight into mechanisms.
In summary, natural LHTL currently provides the best protocol for enhancing endurance performance in elite and subelite athletes, while some artificial protocols are effective in subelite athletes. Likely mediators include V̇O2max and the placebo, nocebo and training-camp effects. Modification of the protocols presents the possibility of further enhancements, which should be the focus of future research.
Acclimatization to moderate high altitude accompanied by training at low altitude (living high-training low) has been shown to improve sea level endurance performance in accomplished, but not elite, runners. Whether elite athletes, who may be closer to the maximal structural and functional adaptive capacity of the respiratory (i.e., oxygen transport from environment to mitochondria) system, may achieve similar performance gains is unclear. To answer this question, we studied 14 elite men and 8 elite women before and after 27 days of living at 2,500 m while performing high-intensity training at 1,250 m. The altitude sojourn began 1 wk after the USA Track and Field National Championships, when the athletes were close to their season's fitness peak. Sea level 3,000-m time trial performance was significantly improved by 1.1% (95% confidence limits 0.3–1.9%). One-third of the athletes achieved personal best times for the distance after the altitude training camp. The improvement in running performance was accompanied by a 3% improvement in maximal oxygen uptake (72.1 ± 1.5 to 74.4 ± 1.5 ml · kg ⁻¹ · min ⁻¹ ). Circulating erythropoietin levels were near double initial sea level values 20 h after ascent (8.5 ± 0.5 to 16.2 ± 1.0 IU/ml). Soluble transferrin receptor levels were significantly elevated on the 19th day at altitude, confirming a stimulation of erythropoiesis (2.1 ± 0.7 to 2.5 ± 0.6 μg/ml). Hb concentration measured at sea level increased 1 g/dl over the course of the camp (13.3 ± 0.2 to 14.3 ± 0.2 g/dl). We conclude that 4 wk of acclimatization to moderate altitude, accompanied by high-intensity training at low altitude, improves sea level endurance performance even in elite runners. Both the mechanism and magnitude of the effect appear similar to that observed in less accomplished runners, even for athletes who may have achieved near maximal oxygen transport capacity for humans.
PURPOSE: Slight physiological differences between acute exposure in normobaric hypoxia (NH) and hypobaric hypoxia (HH) have been reported. Taken together, these differences suggest different physiological responses to hypoxic exposure to a simulated altitude (NH) versus a terrestrial altitude (HH). For this purpose, in the present study, we aimed to directly compare the time-trial performance after acute hypoxia exposure (26 h, 3450 min) by the same subjects under three different conditions: NH, HH, and normobaric normoxia (NN). Based on all of the preceding studies examining the differences among these hypoxic conditions, we hypothesized greater performance impairment in HH than in NH. METHODS: The experimental design consisted of three sessions: NN (Sion: FiO2, 20.93), NH (Sion, hypoxic room: FiO2, 13.6%; barometric pressure, 716 mm Hg), and HH (Jungfraujoch: FiO2, 20.93; barometric pressure, 481 mm Hg). The performance was evaluated at the end of each session with a cycle time trial of 250 kJ. RESULTS: The mean time trial duration in NN was significantly shorter than under the two hypoxic conditions (P < 0.001). In addition, the mean duration in NH was significantly shorter than that in HH (P < 0.01). The mean pulse oxygen saturation during the time trial was significantly lower for HH than for NH (P < 0.05), and it was significantly higher in NN than for the two other sessions (P < 0.001). CONCLUSION: As previously suggested, HH seems to be a more stressful stimulus, and NH and HH should not be used interchangeability when endurance performance is the main objective. The principal factor in this performance difference between hypoxic conditions seemed to be the lower peripheral oxygen saturation in HH at rest, as well as during exercise.
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.
The overall "hypoxic dose" associated with altitude training for athletes is typically reported in the literature as hours of exposure. Current recommendations for altitude training are based around the need to acquire a given number of hours within a specific altitude range (typically 1800-3000 m); with the expected erythropoietic change proportional to the hours accumulated. We propose that elevation should also be incorporated when calculating the total dose of altitude exposure and introduce a new metric termed "kilometer hours" to define overall hypoxic dose.
To investigate physical performance and hematological changes in 32 elite male team-sport players after 14 days of 'live high-train low' (LHTL) in normobaric hypoxia (≥14 h.day at 2800-3000 m) combined with repeated-sprint training (6 sessions of 4 sets of 5 x 5-s sprints with 25 s of passive recovery) either in normobaric hypoxia at 3000 m (LHTL+RSH, namely LHTLH; n = 11) or in normoxia (LHTL+RSN, namely LHTL; n = 12) compared to controlled 'live low-train low' (LLTL; n = 9).
Prior to (Pre-), immediately (Post-1) and 3 weeks (Post-2) after the intervention, hemoglobin mass (Hbmass) was measured in duplicate (optimized carbon monoxide rebreathing method) and vertical jump, repeated-sprint (8 x 20 m - 20 s recovery) and Yo-Yo Intermittent Recovery level 2 (YYIR2) performances were tested.
Both hypoxic groups increased similarly Hbmass at Post-1 and Post-2 in reference to Pre- (LHTLH: +4.0%, P<0.001 and +2.7%, P<0.01; LHTL: +3.0% and +3.0%, both P<0.001), while no change occurred in LLTL. Compared to Pre-, YYIR2 performance increased by ∼21% at Post-1 (P<0.01) and by ∼45% at Post-2 (P<0.001) with no difference between the two intervention groups (vs. no change in LLTL). From Pre- to Post-1 cumulated sprint time decreased in LHTLH (-3.6%, P<0.001) and in LHTL (-1.9%, P<0.01), but not in LLTL (-0.7%), and remained significantly reduced at Post-2 (-3.5% P<0.001) in LHTLH only. Vertical jump performance did not change.
'Live high-train low and high' hypoxic training interspersed with repeated sprints in hypoxia for 14 days (in-season) increases Hbmass, YYIR2 performance and repeated-sprint ability of elite field team-sport players with the benefits lasting for at least three weeks post-intervention.
Background and objective:
Hypoxic training techniques are increasingly used by athletes in an attempt to improve performance in normoxic environments. The 'live low-train high (LLTH)' model of hypoxic training may be of particular interest to athletes because LLTH protocols generally involve shorter hypoxic exposures (approximately two to five sessions per week of <3 h) than other traditional hypoxic training techniques (e.g., live high-train high or live high-train low). However, the methods employed in LLTH studies to date vary greatly with respect to exposure times, training intensities, training modalities, degrees of hypoxia and performance outcomes assessed. Whilst recent reviews provide some insight into how LLTH may be applied to enhance performance, little attention has been given to how training intensity/modality may specifically influence subsequent performance in normoxia. Therefore, this systematic review aims to evaluate the normoxic performance outcomes of the available LLTH literature, with a particular focus on training intensity and modality.
Data sources and study selection:
A systematic search was conducted to capture all LLTH studies with a matched normoxic (control) training group and the assessment of performance under normoxic conditions. Studies were excluded if no training was completed during the hypoxic exposures, or if these exposures exceeded 3 h per day. Four electronic databases were searched (PubMed, SPORTDiscus, EMBASE and Web of Science) during August 2013, and these searches were supplemented by additional manual searches until December 2013.
Results:
After the electronic and manual searches, 40 papers were deemed to meet the inclusion criteria, representing 31 separate studies. Within these 31 studies, four types of LLTH were identified: (1) continuous low-intensity training in hypoxia (CHT, n = 16), (2) interval hypoxic training (IHT, n = 4), (3) repeated sprint training in hypoxia (RSH, n = 3) and (4) resistance training in hypoxia (RTH, n = 4). Four studies also used a combination of CHT and IHT. The majority of studies reported no difference in normoxic performance between the hypoxic and normoxic training groups (n = 19), while nine reported greater improvements in the hypoxic group and three reported poorer outcomes compared with the control group. Selection of training intensity (including matching relative or absolute intensity between normoxic and hypoxic groups) was identified as a key factor in mediating the subsequent normoxic performance outcomes. Five studies included some form of normoxic training for the hypoxic group and 14 studies assessed performance outcomes not specific to the training intensity/modality completed during the training intervention.
Conclusion:
Four modes of LLTH are identified in the current literature (CHT, IHT, RSH and RTH), with training mode and intensity appearing to be key factors in mediating subsequent performance responses in normoxia. Improvements in normoxic performance appear most likely following high-intensity, short-term and intermittent training (e.g., IHT, RSH). LLTH programmes should carefully apply the principles of training and testing specificity and include some high-intensity training in normoxia. For RTH, it is unclear whether the associated adaptations are greater than those of traditional (maximal) resistance training programmes.
Live High: Train Low (LHTL) altitude training is a popular ergogenic aid amongst athletes. An alternative hypoxia protocol, acute (60-90 min daily) Intermittent Hypoxic Exposure (IHE), has shown potential for improving athletic performance. The aim of this study was to compare directly the effects of LHTL and IHE on the running and blood characteristics of elite triathletes. Changes in total haemoglobin mass (Hbmass), maximal oxygen consumption (VO2max), velocity at VO2max(vVO2max), time to exhaustion (TTE), running economy, maximal blood lactate concentration ([La]) and 3 mM [La] running speed were compared following 17 days of LHTL (240 h of hypoxia), IHE (10.2 h of hypoxia) or Placebo treatment in 24 Australian National Team triathletes (7 female, 17 male). There was a clear 3.2 ± 4.8% (mean ± 90% confidence limits) increase in Hbmassfollowing LHTL compared with Placebo, whereas the corresponding change of -1.4 ± 4.5% in IHE was unclear. Following LHTL, running economy was 2.8 ± 4.4% improved compared to IHE and 3mM [La] running speed was 4.4 ± 4.5% improved compared to Placebo. After IHE, there were no beneficial changes in running economy or 3mM [La] running speed compared to Placebo. There were no clear changes in VO2max, vVO2maxand TTE following either method of hypoxia. The clear difference in Hbmassresponse between LHTL and IHE indicated that the dose of hypoxia in IHE was insufficient to induce accelerated erythropoiesis. Improved running economy and 3mM [La] running speed following LHTL suggested that this method of hypoxic exposure may enhance performance at submaximal running speeds. Overall, there was no evidence to support the use of IHE in elite triathletes.
It is unclear if hemoglobin mass (Hbmass) and red cell volume (RCV) increase in endurance athletes with several years of endurance training from adolescence to adulthood. The aim of this study, therefore, was to determine with a controlled cross-sectional approach whether endurance athletes at the ages of 16, 21, and 28 yr are characterized by different Hbmass, RCV, plasma volume (PV), and blood volume (BV).
BV parameters (CO rebreathing), VO(2max) and other blood, iron, training, and anthropometric parameters were measured in three endurance athlete groups AG16 (n = 14), AG21 (n = 14), and AG28 (n = 16) as well as in three age-matched control groups (<2 h endurance training per week): CG16 (n = 16), CG21 (n = 15), and CG28 (n = 16).
In AG16, body weight-related Hbmass (12.4 ± 0.7 g·kg(-1)), RCV, BV, and VO(2max) (66.1 ± 3.8 mL·kg·(-1)min(-1)) were lower (P < 0.001) than those in AG21 (14.2 ± 1.1 g·kg(-1), 72.9 ± 3.6 mL·kg·(-1)min(-1)) and AG28 (14.6 ± 1.1 g·kg(-1), 73.4 ± 6.0 mL·kg·(-1)min(-1)). Results for these parameters did not differ between AG21 and AG28 and among the control groups. VO(2max), PV, and BV were higher for AG16 than for CG16 (12.0 ± 1.0 g·kg(-1), 58.9 ± 5.0 mL·kg·(-1)min(-1)) but not Hbmass and RCV.
Our results suggest that endurance training has major effects on Hbmass and RCV from ages 16 to 21 yr, although there is no further increase from ages 21 to 28 yr in top endurance athletes. On the basis of our findings, an early detection of the aptitude for endurance sports at age 16 yr, solely based on levels of Hbmass, does not seem to be possible.
We sought to determine whether improved cycling performance following ‘Live High-Train Low’ (LHTL) occurs if increases in haemoglobin mass (Hbmass) are prevented via periodic phlebotomy during hypoxic exposure. Eleven, highly trained, female cyclists completed 26 nights of simulated LHTL (16 h day−1, 3000 m). Hbmass was determined in quadruplicate before LHTL and in duplicate weekly thereafter. After 14 nights, cyclists were pair-matched, based on their Hbmass response (ΔHbmass) from baseline, to form a response group (Response, n = 5) in which Hbmass was free to adapt, and a Clamp group (Clamp, n = 6) in which ΔHbmass was negated via weekly phlebotomy. All cyclists were blinded to the blood volume removed. Cycling performance was assessed in duplicate before and after LHTL using a maximal 4-min effort (MMP4min) followed by a ride time to exhaustion test at peak power output (T
lim). VO2peak was established during the MMP4min. Following LHTL, Hbmass increased in Response (mean ± SD, 5.5 ± 2.9%). Due to repeated phlebotomy, there was no ΔHbmass in Clamp (−0.4 ± 0.6%). VO2peak increased in Response (3.5 ± 2.3%) but not in Clamp (0.3 ± 2.6%). MMP4min improved in both the groups (Response 4.5 ± 1.1%, Clamp 3.6 ± 1.4%) and was not different between groups (p = 0.58). T
lim increased only in Response, with Clamp substantially worse than Response (−37.6%; 90% CL −58.9 to −5.0, p = 0.07). Our novel findings, showing an ~4% increase in MMP4min despite blocking an ~5% increase in Hbmass, suggest that accelerated erythropoiesis is not the sole mechanism by which LHTL improves performance. However, increases in Hbmass appear to influence the aerobic contribution to high-intensity exercise which may be important for subsequent high-intensity efforts.
To determine the time course of hemoglobin mass (Hb(mass)) to natural altitude training, Hb(mass), erythropoietin [EPO], reticulocytes, ferritin and soluble transferrin receptor (sTfR) were measured in 13 elite cyclists during, and 10 days after, 3 weeks of sea level (n=5) or altitude (n=8, 2760 m) training. Mean Hb(mass), with a typical error of ∼2%, increased during the first 11 days at altitude (mean ± standard deviation 2.9 ± 2.0%) and was 3.5 ± 2.5% higher than baseline after 19 days. [EPO] increased 64.2 ± 18.8% after 2 nights at altitude but was not different from baseline after 12 nights. Hb(mass) and [EPO] did not increase in sea level. Reticulocytes (%) were slightly elevated in altitude at Days 5 and 12 (18.9 ± 17.7% and 20.4 ± 25.3%), sTfR was elevated at Day 12 (18.9 ± 15.0%), but both returned to baseline by Day 20. Hb(mass) and [EPO] decreased on descent to sea level while ferritin increased. The mean increase in Hb(mass) observed after 11 days (∼300 h) of altitude training was beyond the measurement error and consitent with the mean increase after 300 h of simulated live high:train low altitude. Our results suggest that in elite cyclists, Hb(mass) increases progressively with 3 weeks of natural altitude exposure, with greater increases expected as exposure persists.
SCHMIDT, W. and N. PROMMER. Impact of alterations in total hemoglobin mass on (V) over dotO(2max). Exerc. Sport Sci. Rev., Vol. 38, No. 2, pp. 68-75, 2010. Training and hypoxia-associated changes in maximal oxygen uptake are mediated by different blood adaptations. Training increases blood volume because of plasma and red cell volume expansion, resulting in increased cardiac output, whereas hypoxia increases only red cell volume, leading to increased hemoglobin concentration and oxygen transport capacity. Blood doping mimics the altitude effects, however, by far exceeding its magnitude.
The effect of repeated exposures to natural and simulated moderate altitude on physiology and competitive performance of elite athletes warrants further investigation. This study quantified changes in hemoglobin mass, performance tests, and competitive performance of elite swimmers undertaking a coach-prescribed program of natural and simulated altitude training. Nine swimmers (age 21.1 +/- 1.4 years, mean +/- SD) completed up to four 2-week blocks of combined living and training at moderate natural altitude (1,350 m) and simulated live high-train low (2,600-600 m) altitude exposure between 2 National Championships. Changes in hemoglobin mass (Hbmass), 4-mM lactate threshold velocity, and 2,000 m time trial were measured. Competition performance of these swimmers was compared with that of 9 similarly trained swimmers (21.1 +/- 4.1 years) who undertook no altitude training. Each 2-week altitude block on average produced the following improvements: Hbmass, 0.9% (90% confidence limits, +/-0.8%); 4-mM lactate threshold velocity, 0.9% (+/-0.8%); and 2,000 m time trial performance, 1.2% (+/-1.6%). The increases in Hbmass had a moderate correlation with time trial performance (r = 0.47; +/-0.41) but an unclear correlation with lactate threshold velocity (r = -0.23; +/-0.48). The altitude group did not swim faster at National Championships compared with swimmers who did not receive any altitude exposure, the difference between the groups was not substantial (-0.5%; +/-1.0%). A coach-prescribed program of repeated altitude training and exposure elicited modest changes in physiology but did not substantially improve competition performance of elite swimmers. Sports should investigate the efficacy of their altitude training program to justify the investment.
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.
Statistical guidelines and expert statements are now available to assist in the analysis and reporting of studies in some biomedical disciplines. We present here a more progressive resource for sample-based studies, meta-analyses, and case studies in sports medicine and exercise science. We offer forthright advice on the following controversial or novel issues: using precision of estimation for inferences about population effects in preference to null-hypothesis testing, which is inadequate for assessing clinical or practical importance; justifying sample size via acceptable precision or confidence for clinical decisions rather than via adequate power for statistical significance; showing SD rather than SEM, to better communicate the magnitude of differences in means and nonuniformity of error; avoiding purely nonparametric analyses, which cannot provide inferences about magnitude and are unnecessary; using regression statistics in validity studies, in preference to the impractical and biased limits of agreement; making greater use of qualitative methods to enrich sample-based quantitative projects; and seeking ethics approval for public access to the depersonalized raw data of a study, to address the need for more scrutiny of research and better meta-analyses. Advice on less contentious issues includes the following: using covariates in linear models to adjust for confounders, to account for individual differences, and to identify potential mechanisms of an effect; using log transformation to deal with nonuniformity of effects and error; identifying and deleting outliers; presenting descriptive, effect, and inferential statistics in appropriate formats; and contending with bias arising from problems with sampling, assignment, blinding, measurement error, and researchers' prejudices. This article should advance the field by stimulating debate, promoting innovative approaches, and serving as a useful checklist for authors, reviewers, and editors.
It is controversially discussed whether soccer games should be played at moderate (2001-3000 m) and high altitudes (3001-5500 m) or should be restricted to near sea level and low altitude (501-2000 m) conditions. Athletes living at altitude are assumed to have a performance advantage compared with lowlanders. One advantage of altitude adaptation concerns the expansion of total hemoglobin mass (tHb-mass), which is strongly related to endurance performance at sea level. Cross-sectional studies show that elite athletes posses approximately 35% higher tHb-mass than the normal population, which is further elevated by 14% in athletes native to altitude of 2600 m. Although the impact of this huge tHb-mass expansion on performance is not yet investigated for altitude conditions, lowland athletes seek for possibilities to increase tHb-mass to similar levels. At sea level tHb-mass is only moderately influenced by training and depends more on genetic predisposition. Altitude training in contrast, using either the conventional altitude training or the live high-train low (>14 h/day in hypoxia) protocol for 3-4 weeks above 2500 m leads to mean increases in tHb-mass of 6.5%. This increase is, however, not sufficient to close the gap in tHb-mass to elite athletes native to altitude, which may be in advantage when tHb-mass has the same strong influence on aerobic performance at altitude as it has on sea level.
For decades altitude training has been used by endurance athletes and coaches to enhance sea-level performance. Whether altitude training does, in fact, enhance sea level performance and, if so, by what means has been the subject of a number of investigations. Data produced principally by Levine and Stray-Gundersen have shown that living for 4 weeks at 2500 m, while performing the more intense training sessions near sea level will provide an average improvement in sea level endurance performance (duration of competition: 7-20 min) of approximately 1.5%, ranging from no improvement to 6% improvement. This benefit lasts for at least 3 weeks on return to sea level. Two mechanisms have been shown to be associated with improvement in performance. One is an increase in red cell mass ( approximately 8%) that results in an improved maximal oxygen uptake ( approximately 5%). That must be combined with maintenance of training velocities and oxygen flux to realize the improvement in subsequent sea level performance. We find no evidence of changes in running economy or markers of anaerobic energy utilization. Our results have been obtained in runners ranging from collegiate to elite. Wehrlin et al. have recently confirmed these results in elite orienteers. While there are no specific studies addressing the use of living high, training low in football players, it is likely that an improvement in maximal oxygen uptake, all other factors equal, would enhance football performance. This benefit must be weighed against the time away (4 weeks) from home and competition necessary to gain these benefits.
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.
Haemoglobin mass (Hb mass), maximum oxygen consumption (VO2max), simulated 4000 m individual pursuit cycling performance (IP4000), and haematological markers of red blood cell (RBC) turnover were measured in 8 male cyclists before and after (A) 31 d of altitude training at 2690 m. The dependent variables were measured serially after altitude on d A3-4, A8-9 and A20-21. There was no significant change in Hb mass over the course of the study and VO2max at d A9 was significantly lower than the baseline value (79.3 +/- 0.7 versus 81.4 +/- 0.6 ml x kg(-1) x min(-1), respectively). No increase in Hb mass or VO2max was probably due to initial values being close to the natural physiological limit with little scope for further change. When the IP4000 was analysed as a function of the best score on any of the three test days after altitude training there was a 4% improvement that was not reflected in a corresponding change in VO2max or Hb mass. RBC creatine concentration was significantly reduced after altitude training, suggesting a decrease in the average age of the RBC population. However, measurement of reticulocyte number and serum concentrations of erythropoietin, haptoglobin and bilirubin before and after altitude provided no evidence of increased RBC turnover. The data suggest that for these elite cyclists any benefit of altitude training was not from changes in VO2max or Hb mass, although this does not exclude the possibility of improved anaerobic capacity.
Reliability refers to the reproducibility of values of a test, assay or other measurement in repeated trials on the same individuals. Better reliability implies better precision of single measurements and better tracking of changes in measurements in research or practical settings. The main measures of reliability are within-subject random variation, systematic change in the mean, and retest correlation. A simple, adaptable form of within-subject variation is the typical (standard) error of measurement: the standard deviation of an individual's repeated measurements. For many measurements in sports medicine and science, the typical error is best expressed as a coefficient of variation (percentage of the mean). A biased, more limited form of within-subject variation is the limits of agreement: the 95% likely range of change of an individual's measurements between 2 trials. Systematic changes in the mean of a measure between consecutive trials represent such effects as learning, motivation or fatigue; these changes need to be eliminated from estimates of within-subject variation. Retest correlation is difficult to interpret, mainly because its value is sensitive to the heterogeneity of the sample of participants. Uses of reliability include decision-making when monitoring individuals, comparison of tests or equipment, estimation of sample size in experiments and estimation of the magnitude of individual differences in the response to a treatment. Reasonable precision for estimates of reliability requires approximately 50 study participants and at least 3 trials. Studies aimed at assessing variation in reliability between tests or equipment require complex designs and analyses that researchers seldom perform correctly. A wider understanding of reliability and adoption of the typical error as the standard measure of reliability would improve the assessment of tests and equipment in our disciplines.