No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Hypoxic Training Is Beneficial in Elite Athletes
... Many competitive endurance athletes undertake training camps in hypoxic conditions to increase hemoglobin mass (Hb mass ) in order to improve oxygen carrying capacity and endurance performance. 1,2 Training and living at moderate altitude (1800-2500 m) has often been used as a hypoxic stimulus for potential performance benefits. 3 In addition, generators can be used to simulate a normobaric hypoxic environment at sea level, which provides a logistically convenient option for transitioning between normoxic and hypoxic conditions. ...
... Although altitude training theoretically increases endurance performance, scientific evidence is controversial. 2,12,13 In addition, research on normobaric LHTLH is limited, even though it is implemented by athletes. Thus, the aim of this study is to investigate whether 4 weeks of normobaric LHTLH during a preparation season causes different hematological, cardiorespiratory, and sea-level performance changes in national and international level XC skiers compared to the skiers who live and train in normoxia. ...
... Despite several studies having reported the effectiveness of LHTL on endurance performance, results remain controversial. 2,13 Our findings are in line with previous research that suggests that LHTL does not increase exercise performance and should not be recommended for endurance athletes. 12,13,23,24 Nevertheless, other literature describes the performance benefits of LHTL. 2 For example, Hauser et al. 25 found that 3 km running performance increased more in male triathletes F I G U R E 2 Changes in maximal oxygen uptake (VO 2max ) (A) and time to exhaustion (TTE) (B) during 4-week period either in normobaric hypoxia (LHTLH) or in normoxia (CON). ...
Purpose
To investigate whether 4 weeks of normobaric “live high–train low and high” (LHTLH) causes different hematological, cardiorespiratory, and sea‐level performance changes compared to living and training in normoxia during a preparation season.
Methods
Nineteen (13 women, 6 men) cross‐country skiers competing at the national or international level completed a 28‐day period (∼18 h day⁻¹) of LHTLH in normobaric hypoxia of ∼2400 m (LHTLH group) including two 1 h low‐intensity training sessions per week in normobaric hypoxia of 2500 m while continuing their normal training program in normoxia. Hemoglobin mass (Hbmass) was assessed using a carbon monoxide rebreathing method. Time to exhaustion (TTE) and maximal oxygen uptake (VO2max) were measured using an incremental treadmill test. Measurements were completed at baseline and within 3 days after LHTLH. The control group skiers (CON) (seven women, eight men) performed the same tests while living and training in normoxia with ∼4 weeks between the tests.
Results
Hbmass in LHTLH increased 4.2 ± 1.7% from 772 ± 213 g (11.7 ± 1.4 g kg⁻¹) to 805 ± 226 g (12.5 ± 1.6 g kg⁻¹) (p < 0.001) while it was unchanged in CON (p = 0.21). TTE improved during the study regardless of the group (3.3 ± 3.4% in LHTLH; 4.3 ± 4.8% in CON, p < 0.001). VO2max did not increase in LHTLH (61.2 ± 8.7 mL kg⁻¹ min⁻¹ vs. 62.1 ± 7.6 mL kg⁻¹ min⁻¹, p = 0.36) while a significant increase was detected in CON (61.3 ± 8.0–64.0 ± 8.1 mL kg⁻¹ min⁻¹, p < 0.001).
Conclusions
Four‐week normobaric LHTLH was beneficial for increasing Hbmass but did not support the short‐term development of maximal endurance performance and VO2max when compared to the athletes who lived and trained in normoxia.
... There are many benefits of hypoxia, such as helping weight loss, maintaining cardio-metabolic health (Kayser and Verges, 2013;Woolcott et al., 2015;Hobbins et al., 2017), as well as improving exercise performance (Girard et al., 2013a,b;Wang et al., 2019). Exercise training under hypoxic conditions has been widely accepted as a mean to enhance athletic endurance ability in the past few decades (Girard et al., 2013a;Millet and Brocherie, 2020). The predominant mechanisms of hypoxic training on improving sports performance focused on hematological factors such as increased red blood cell (RBC) counts and high hemoglobin (HGB) concentrations, as well as non-hematological factors including running economy, lactate threshold, mitochondrial gene expression, and enhanced muscle buffering capacity (Saunders et al., 2013;Mujika et al., 2019). ...
... Moderate altitude training has emerged as a popular method to improve athletic endurance performance (Girard et al., 2013a;Millet and Brocherie, 2020). However, the underlying mechanisms have not been fully clarified (Girard et al., 2013a;Zhao et al., 2018;Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020). ...
... Moderate altitude training has emerged as a popular method to improve athletic endurance performance (Girard et al., 2013a;Millet and Brocherie, 2020). However, the underlying mechanisms have not been fully clarified (Girard et al., 2013a;Zhao et al., 2018;Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020). Recent evidence indicated that exercise and the gut microbiota were interconnected (Przewłócka et al., 2020;Clauss et al., 2021). ...
Hypoxia environment has been widely used to promote exercise capacity. However, the underlying mechanisms still need to be further elucidated. In this study, mice were exposed to the normoxia environment (21% O 2 ) or hypoxia environment (16.4% O 2 ) for 4 weeks. Hypoxia-induced gut microbiota remodeling characterized by the increased abundance of Akkermansia and Bacteroidetes genera, and their related short-chain fatty acids (SCFAs) production. It was observed that hypoxia markedly improved endurance by significantly prolonging the exhaustive running time, promoting mitochondrial biogenesis, and ameliorating exercise fatigue biochemical parameters, including urea nitrogen, creatine kinase, and lactic acid, which were correlated with the concentrations of SCFAs. Additionally, the antibiotics experiment partially inhibited hypoxia-induced mitochondrial synthesis. The microbiota transplantation experiment demonstrated that the enhancement of endurance capacity induced by hypoxia was transferable, indicating that the beneficial effects of hypoxia on exercise performance were partly dependent on the gut microbiota. We further identified that acetate and butyrate, but not propionate, stimulated mitochondrial biogenesis and promoted endurance performance. Our results suggested that hypoxia exposure promoted endurance capacity partially by the increased production of SCFAs derived from gut microbiota remodeling.
... Different hypoxic training techniques have been developed, aimed at producing these physiological adaptations, by combining varying doses of hypoxia and training. The combination of high-intensity training with hypoxic conditions, to reduce the time required (of training or exposure) to achieve the proposed benefits, has been proposed for athletes across different sporting modalities (Millet & Brocherie, 2020). While some studies report improvements in the haematological status following high-intensity training in hypoxia (Buchheit et al., 2013;Faiss et al., 2014), others have not demonstrated benefits (Morton & Cable, 2005). ...
... In active subjects and team sport players, the large effect sizes observed suggest that the RSH protocol of this study can produce increases in haematological parameters. Current literature indicates that RSH can provoke a haematological response through specific mechanisms, which are not observed with passive hypoxic exposure or with lower training intensities (Millet & Brocherie, 2020). These increases in the active and team sport RSH groups, particularly the post-2 time point, could be due to the transcriptional and vascular responses, which improve the behaviour of fast-twitch fibres. ...
... Based on these results, 4 weeks of RSH combined with routine endurance training could be sufficient to alleviate any adverse effects that endurance athletes may experience from repeated sprint training alone or in normoxia. Furthermore, RSH has been proposed as an effective strategy for improving sport-specific physical performance (Brocherie et al., 2017), with maladaptation to RSH having not been identified yet (Millet & Brocherie, 2020). Therefore, RSH may be recommended to complement the regular training of endurance athletes due to potential improvements in performance, with maintenance of haematological parameters. ...
The aim was to determine the effects of repeated-sprint training in hypoxia on haematocrit and haemoglobin in different sporting modalities. Seventy-two participants were randomly allocated to Active-Repeated sprint in hypoxia (A-RSH, n= 8); Active-Repeated sprint in normoxia (A-RSN, n= 8); Active-Control (A-CON, n= 8); Team Sports-RSH (T-RSH, n= 8); Team Sports-RSN (T-RSN, n= 8); Team Sports-Control (T-CON, n= 8); Endurance-RSH (E-RSH, n= 8); Endurance-RSN (E-RSN, n= 8); Endurance-Control (E-CON, n= 8). Sessions consisted of two sets of five sprints of 10 swith recovery of 20 sbetween sprints and 10 min between sets. Blood samples for haematocrit and haemoglobin concentrations were obtained before and after, and 2 weeks after cessation. Haematocrit and haemoglobin were lower for the E-RSN group following 2 weeks of cessation of protocol compared with E-RSH (p = 0.035) and E-CON (p = 0.045). Haematocrit of the A-RSH group was higher compared with baseline (p = 0.05) and Post (p = 0.05). Similarly, the T-RSH group demonstrated increases in haematocrit following 2 weeks of cessation compared with Post (p = 0.04). Repeated Sprint Training in Hypoxia had different haematological effects depending on sporting modality.
... However, highintensity training under hypoxic conditions (e.g. repeated sprint training in hypoxia) [33][34][35][36] or a combination of hypoxic methods [1,37] seems a promising approach for performance enhancement in moderately to well-trained populations and elite athletes. Nevertheless, it has also been stated that the use of hypoxic training methods (whether at rest or in combination with exercise) has been strongly promoted in elite athletes for many years without any evidence for their justification, which is still under debate [36,38]. ...
... repeated sprint training in hypoxia) [33][34][35][36] or a combination of hypoxic methods [1,37] seems a promising approach for performance enhancement in moderately to well-trained populations and elite athletes. Nevertheless, it has also been stated that the use of hypoxic training methods (whether at rest or in combination with exercise) has been strongly promoted in elite athletes for many years without any evidence for their justification, which is still under debate [36,38]. Studies conducted with healthy non-athletic populations have shown that IH at rest or in combination with physical exercises can be a valuable strategy to improve cognitive functions (e.g. ...
Background
Intermittent hypoxia applied at rest or in combination with exercise promotes multiple beneficial adaptations with regard to performance and health in humans. It was hypothesized that replacing normoxia by moderate hyperoxia can increase the adaptive response to the intermittent hypoxic stimulus.
Objective
Our objective was to systematically review the current state of the literature on the effects of chronic intermittent hypoxia–hyperoxia (IHH) on performance- and health-related outcomes in humans.
Methods
PubMed, Web of Science™, Scopus, and Cochrane Library databases were searched in accordance with PRISMA guidelines (January 2000 to September 2021) using the following inclusion criteria: (1) original research articles involving humans, (2) investigation of the chronic effect of IHH, (3) inclusion of a control group being not exposed to IHH, and (4) articles published in peer-reviewed journals written in English.
Results
Of 1085 articles initially found, eight studies were included. IHH was solely performed at rest in different populations including geriatric patients ( n = 1), older patients with cardiovascular ( n = 3) and metabolic disease ( n = 2) or cognitive impairment ( n = 1), and young athletes with overtraining syndrome ( n = 1). The included studies confirmed the beneficial effects of chronic exposure to IHH, showing improvements in exercise tolerance, peak oxygen uptake, and global cognitive functions, as well as lowered blood glucose levels. A trend was discernible that chronic exposure to IHH can trigger a reduction in systolic and diastolic blood pressure. The evidence of whether IHH exerts beneficial effects on blood lipid levels and haematological parameters is currently inconclusive. A meta-analysis was not possible because the reviewed studies had a considerable heterogeneity concerning the investigated populations and outcome parameters.
Conclusion
Based on the published literature, it can be suggested that chronic exposure to IHH might be a promising non-pharmacological intervention strategy for improving peak oxygen consumption, exercise tolerance, and cognitive performance as well as reducing blood glucose levels, and systolic and diastolic blood pressure in older patients with cardiovascular and metabolic diseases or cognitive impairment. However, further randomized controlled trials with adequate sample sizes are needed to confirm and extend the evidence. This systematic review was registered on the international prospective register of systematic reviews (PROSPERO-ID: CRD42021281248) ( https://www.crd.york.ac.uk/prospero/ ).
... Altitude training is a common strategy employed by elite endurance athletes to induce physiological adaptations, with a potential to improve subsequent performance at altitude and/or sea level. [1][2][3] Thus, elite endurance athletes commonly integrate training camps at low-to-moderate altitudes (eg, » 1400-2500 m) lasting 2À4 weeks into their annual training periodization. 2 The most extensively studied adaptive response linked to altitude training is the erythropoietin-driven increases in red blood cell volume and total hemoglobin mass. 2 Although there are conflicting views, 3,4 these hematological changes are considered to represent the main mechanism for improved endurance performance at sea level following periods of altitude training. 2 Optimization of altitude adaptations depends on various factors, such as the hypoxic dose, training load and recovery, oxygen saturation (SpO 2 ), iron and energy availability and illness status. ...
... Altitude training is a common strategy employed by elite endurance athletes to induce physiological adaptations, with a potential to improve subsequent performance at altitude and/or sea level. [1][2][3] Thus, elite endurance athletes commonly integrate training camps at low-to-moderate altitudes (eg, » 1400-2500 m) lasting 2À4 weeks into their annual training periodization. 2 The most extensively studied adaptive response linked to altitude training is the erythropoietin-driven increases in red blood cell volume and total hemoglobin mass. 2 Although there are conflicting views, 3,4 these hematological changes are considered to represent the main mechanism for improved endurance performance at sea level following periods of altitude training. 2 Optimization of altitude adaptations depends on various factors, such as the hypoxic dose, training load and recovery, oxygen saturation (SpO 2 ), iron and energy availability and illness status. ...
Objectives:
To observe changes in sleep from baseline and during an altitude training camp in elite endurance athletes.
Design:
Prospective, observational.
Setting:
Baseline monitoring at <500 m for 2 weeks and altitude monitoring at 1800 m for 17-22 days.
Participants:
Thirty-three senior national-team endurance athletes (mean age 25.8 ± S.D. 2.8 years, 16 women).
Measurements:
Daily measurements of sleep (using a microwave Doppler radar at baseline and altitude), oxygen saturation (SpO2), training load and subjective recovery (at altitude).
Results:
At altitude vs. baseline, sleep duration (P = .036) and light sleep (P < .001) decreased, while deep sleep (P < .001) and respiration rate (P = .020) increased. During the first altitude week vs. baseline, deep sleep increased (P = .001). During the first vs. the second and third altitude weeks, time in bed (P = .005), sleep duration (P = .001), and light sleep (P < .001) decreased. Generally, increased SpO2 was associated with increased deep sleep while increased training load was associated with increased respiration rate.
Conclusion:
This is the first study to document changes in sleep from near-sea-level baseline and during a training camp at 1800 m in elite endurance athletes. Ascending to altitude reduced total sleep time and light sleep, while deep sleep and respiration rate increased. SpO2 and training load at altitude were associated with these responses. This research informs our understanding of the changes in sleep occurring in elite endurance athletes attending training camps at competition altitudes.
... T he main aim of performing altitude training (AT) was to improve the aerobic capacity of athletes at sea level (Suzuki et al., 2014;Rodriguez et al., 2015). However, whether athletes benefit from AT or not is still controversial (Robach and Lundby, 2012;Lundby and Robach, 2016;Diebel et al., 2017;Millet and Brocherie, 2020). The reasons for varied results of AT in different studies are complicated. ...
... Since the 1968 Mexico City Olympics, studies that use AT to enhance the endurance performance of athletes have emerged; currently, these training methods are commonly being applied by many athletes and coaches. In fact, whether athletes' performance improved from AT or not is still controversial (Robach and Lundby, 2012;Lundby and Robach, 2016;Diebel et al., 2017;Millet and Brocherie, 2020). Using meta-analysis, Park et al. (2016) found that AT appears to be more effective than ST for improvement of aerobic capacity (Park et al., 2016). ...
Meng, Zhijun, Huan Gao, Tao Li, Peng Ge, Yixiao Xu, and Binghong Gao. Effects of eight weeks altitude training on the aerobic capacity and microcirculation function in trained rowers. High Alt Med Biol 00:000-000, 2020.
Background:
The mechanism of aerobic improvement after altitude training (AT) has not been resolved yet. Few studies have looked at microcirculation changes after AT in athletes.
Materials and Methods:
Thirty-three male rowers were recruited and divided into either the AT (n = 18, altitude 2,280 m) or the sea level training (ST group, n = 15, altitude 50 m) for 8 weeks training. Microcirculation function was monitored using a laser Doppler flowmeter. VO2peak and ergometer 5 km time trial (Er5k) were conducted.
Results:
Within the AT group there was an 8.8% increment in VO2peak from pre- to post-training (4,708.9 ± 455.2 vs. 5,123.3 ± 391.2 ml/min, p < 0.01), whereas in ST group there was a 3.1% increase of VO2peak from pre- to post-training (4,975.4 ± 501.1 vs. 5,128.0 ± 499.3 m/min, p = 0.125). Er5k performance in AT group was significantly improved (1,040.3 ± 26.3 vs. 1,033.2 ± 27.5 seconds, p = 0.038), whereas in ST group Er5k performance was not improved (1,059.6 ± 30.9 vs. 1,060.4 ± 33.2 seconds, p = 0.819). Postocclusive reactive hyperemia reserve and heat reserve in the forearm of AT subjects increased significantly after 8 weeks. Meanwhile, the AT group's resting blood flow and cutaneous vascular conductance (CVC) of the thigh were higher after AT. For the ST group, resting blood flow and CVC in the thigh decreased significantly at third week post-training. There was a low correlation between the change of VO2peak and blood flow of the thigh (r = 0.45, p = 0.01).
Conclusions:
Trained rowers benefit more from 8 weeks of AT than from 8 weeks ST in terms of aerobic capacity. We have found that 8 weeks of AT increases thigh blood flow and improves endothelial function.
... Although AT has been extensively applied and is trusted by coaches and athletes (Daniels and Oldridge, 1970;Solli et al., 2017), its effectiveness on aerobic performance remains unclear (Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020). In general, the ambiguity originates from two aspects: 1) Potential negative effects of chronic hypoxia exposure (various types of acute altitude sickness) (Imray et al., 2010;Schommer et al., 2012), which outweighs potential benefits and 2) unreasonable hypoxic doses . ...
Objective: This study aimed to compare and rank the effect of hypoxic practices on maximum oxygen consumption (VO 2 max) in athletes and determine the hypoxic dose-response correlation using network meta-analysis.
Methods: The Web of Science, PubMed, EMBASE, and EBSCO databases were systematically search for randomized controlled trials on the effect of hypoxc interventions on the VO 2 max of athletes published from inception until 21 February 2023. Studies that used live-high train-high (LHTH), live-high train-low (LHTL), live-high, train-high/low (HHL), intermittent hypoxic training (IHT), and intermittent hypoxic exposure (IHE) interventions were primarily included. LHTL was further defined according to the type of hypoxic environment (natural and simulated) and the altitude of the training site (low altitude and sea level). A meta-analysis was conducted to determine the standardized mean difference between the effects of various hypoxic interventions on VO 2 max and dose-response correlation. Furthermore, the hypoxic dosage of the different interventions were coordinated using the “kilometer hour” model.
Results: From 2,072 originally identified titles, 59 studies were finally included in this study. After data pooling, LHTL, LHTH, and IHT outperformed normoxic training in improving the VO 2 max of athletes. According to the P-scores, LHTL combined with low altitude training was the most effective intervention for improving VO 2 max (natural: 0.92 and simulated: 0.86) and was better than LHTL combined with sea level training (0.56). A reasonable hypoxic dose range for LHTH (470–1,130 kmh) and HL (500–1,415 kmh) was reported with an inverted U-shaped curve relationship.
Conclusion: Different types of hypoxic training compared with normoxic training serve as significant approaches for improving aerobic capacity in athletes. Regardless of the type of hypoxic training and the residential condition, LHTL with low altitude training was the most effective intervention. The characteristics of the dose-effect correlation of LHTH and LHTL may be associated with the negative effects of chronic hypoxia.
... Importantly, the quality of sleep and recovery is well preserved, as athletes do not sleep in hypoxic conditions [10]. However, published data reported inconclusive effectiveness of IHT in improving VO 2 max and hematological parameters [13,14]. After IHT, improvements in aerobic and anaerobic capacity are reported [15,16], no effects [17] or even negative effects of this training are indicated (reduced speeds and power output, reduced oxygen flux in athletes) [18]. ...
The aim of study was to evaluate the effects of interval training performed in hypoxia on aerobic capacity and second ventilatory threshold in young, untrained men. Participants (n = 48) were randomly divided into a control group and two groups performing the same interval training (three times a week for 4 weeks) in normoxia (200 m asl) (NT) and in hypoxia (IHT) (3000 m asl, FIO2 = 14.4%). In the incremental test, maximal oxygen uptake (VO2max) was measured and the first (VT1) and second (VT2) ventilatory thresholds and the maximal power output (Pmax) were determined for each participant. The training workloads of the efforts corresponded to the workload at VT2 (effort) and VT1 (active recovery). Training in both normoxia and hypoxia significantly increased absolute VO2max (p = 0.02, ES = 0.51 and p = 0.002, ES = 0.47, respectively). In comparison to NT, only IHT significantly (p < 0.001; ES = 0.80) improved Pmax, as well as power at VT2 (p = 0.02; ES = 0.78). The applied IHT was effective in improving Pmax and power at VT2, which was not observed after training in normoxia.
... Despite the activation of HIFs by exercise and although exercise in hypoxic conditions has become an important training modality, as preparation for competitions in high altitude [186], to increase general athletic performance (although this remains debated [187,188]) or as a potential alternative to heavy training for load-compromised individuals [189], the interplay of mitochondria and HIFs during exercise is not well understood yet. ...
Reduced oxygen availability (hypoxia) can lead to cell and organ damage. Therefore, aerobic species depend on efficient mechanisms to counteract detrimental consequences of hypoxia. Hypoxia inducible factors (HIFs) and mitochondria are integral components of the cellular response to hypoxia and coordinate both distinct and highly intertwined adaptations. This leads to reduced dependence on oxygen, improved oxygen supply, maintained energy provision by metabolic remodeling and tapping into alternative pathways and increased resilience to hypoxic injuries. On one hand, many pathologies are associated with hypoxia and hypoxia can drive disease progression, for example in many cancer and neurological diseases. But on the other hand, controlled induction of hypoxia responses via HIFs and mitochondria can elicit profound health benefits and increase resilience. To tackle pathological hypoxia conditions or to apply health-promoting hypoxia exposures efficiently, cellular and systemic responses to hypoxia need to be well understood. Here we first summarize the well-established link between HIFs and mitochondria in orchestrating hypoxia-induced adaptations and then outline major environmental and behavioral modulators of their interaction that remain poorly understood.
... On the other hand, living or training in high altitude or artificial hypoxia are commonly used to improve athlete performance [15,16]. Intermittent hypoxia exposure is also applied to increase human tolerance to high altitude [2,[16][17][18][19][20] and may even have therapeutic value in numerous diseases [4,18,21]. ...
Older individuals represent a growing population, in industrialized countries, particularly those with cardiovascular diseases, which remain the leading cause of death in western societies. Aging constitutes one of the largest risks for cardiovascular diseases. On the other hand, oxygen consumption is the foundation of cardiorespiratory fitness, which in turn is linearly related to mortality, quality of life and numerous morbidities. Therefore, hypoxia is a stressor that induces beneficial or harmful adaptations, depending on the dose. While severe hypoxia can exert detrimental effects, such as high-altitude illnesses, moderate and controlled oxygen exposure can potentially be used therapeutically. It can improve numerous pathological conditions, including vascular abnormalities, and potentially slows down the progression of various age-related disorders. Hypoxia can exert beneficial effects on inflammation, oxidative stress, mitochondrial functions, and cell survival, which are all increased with age and have been discussed as main promotors of aging. This narrative review discusses specificities of the aging cardiovascular system in hypoxia. It draws upon an extensive literature search on the effects of hypoxia/altitude interventions (acute, prolonged, or intermittent exposure) on the cardiovascular system in older individuals (over 50 years old). Special attention is directed toward the use of hypoxia exposure to improve cardiovascular health in older individuals.
... It is concluded that HIIT sessions with different work and recovery intensity and duration induced similar adaptations in highly trained rowers. This suggests that as long as HIIT sessions are performed in the same intensity domain, the exact determination of the interval parameters may be of lesser importance than other well-established influential factors (eg, rate of training volume progression, training intensity distribution, altitude training 12,13 ) for the development of aerobic qualities in endurance athletes. Abbreviations: A 1 , amplitude; τ 1 , time constant of the primary phase of the VO 2 kinetics; A 2 , amplitude of the slow component phase (in percentage of the overall change in VO 2 ); HIIT, high-intensity interval training; ILT, individual lactate threshold; PAP, peak aerobic power; TD 1 , time delay; VO 2 kinetics, oxygen uptake kinetics. ...
Purpose:
Oxygen uptake kinetics (VO2kinetics) is a measure of an athlete's capacity to respond to variations in energy demands. Faster VO2kinetics is associated with better performance in endurance sports, but optimal training methods to improve VO2kinetics remain unclear. This study compared the effects of 2 high-intensity interval-training (HIIT) programs on traditional rowing performance and VO2kinetics.
Methods:
Twelve highly trained rowers performed one of two 6-week HIIT protocols: either 3-minute repetitions at 90% (HIIT90; n = 5) of peak aerobic power (PAP) or 90-second repetitions at 100% (HIIT100; n = 7) of PAP. Before (PRE) and after (POST) the training intervention, they performed an incremental test to exhaustion to determine the individual lactate threshold, onset of blood lactate accumulation and PAP, and two 6-minute rest-to-exercise transitions to determine VO2kinetics.
Results:
No significant changes (P > .05) were observed for rowing ergometer power output at individual lactate threshold (HIIT90 PRE 255 [12], POST 264 [13]; HIIT100 247 [24], 266 [28] W), onset of blood lactate accumulation (279 [12], 291 [16]; 269 [23], 284 [32] W), or PAP (359 [13], 381 [15]; 351 [21], 363 [29] W) or for any parameters of VO2kinetics. No differences were observed between HIIT interventions.
Conclusion:
The HIIT interventions did not induce significant performance or VO2kinetics improvements, although mean power output at individual lactate threshold, onset of blood lactate accumulation, and PAP increased by 5.7%, 5.0%, and 4.5%, respectively. This suggests that the exact intensity and duration of HIIT sessions performed in the same intensity domain may be of lesser importance than other well-established influential factors (eg, training volume progression, training intensity distribution, altitude training) to develop aerobic qualities in endurance athletes.
... Altitude hypoxia training has become a popular means to increase endurance athletes' performance for decades (18)(19)(20)(21)(22). What's more, current research indicates that chronic intermittent hypoxic-hyperoxic periods exposure at rest is beneficial for older patients with cardiovascular and metabolic diseases or cognitive impairment to improve physical and cognitive performance and reduce cardiometabolic risk factors (23). Despite much research in this area to date, the results are highly controversial as intraindividual and interindividual variabilities (24,25). More studies are needed to confirm and extend the evidence. ...
Introduction
Musculoskeletal system gradually degenerates with aging, and a hypoxia environment at a high altitude may accelerate this process. However, the comprehensive effects of high-altitude environments on bones and muscles remain unclear. This study aims to compare the differences in bones and muscles at different altitudes, and to explore the mechanism and influencing factors of the high-altitude environment on the skeletal muscle system.
Methods
This is a prospective, multicenter, cohort study, which will recruit a total of 4000 participants over 50 years from 12 research centers with different altitudes (50m~3500m). The study will consist of a baseline assessment and a 5-year follow-up. Participants will undergo assessments of demographic information, anthropomorphic measures, self-reported questionnaires, handgrip muscle strength assessment (HGS), short physical performance battery (SPPB), blood sample analysis, and imaging assessments (QCT and/or DXA, US) within a time frame of 3 days after inclusion. A 5-year follow-up will be conducted to evaluate the changes in muscle size, density, and fat infiltration in different muscles; the muscle function impairment; the decrease in BMD; and the osteoporotic fracture incidence. Statistical analyses will be used to compare the research results between different altitudes. Multiple linear, logistic regression and classification tree analyses will be conducted to calculate the effects of various factors (e.g., altitude, age, and physical activity) on the skeletal muscle system in a high-altitude environment. Finally, a provisional cut-off point for the diagnosis of sarcopenia in adults at different altitudes will be calculated.
Ethics and dissemination
The study has been approved by the institutional research ethics committee of each study center (main center number: KHLL2021-KY056). Results will be disseminated through scientific conferences and peer-reviewed publications, as well as meetings with stakeholders.
Clinical Trial registration number
http://www.chictr.org.cn/index.aspx , identifier ChiCTR2100052153.
... The benefits of altitude training for endurance athletes are still debated in the scientific literature 4,5 ; however, it is a common practice, particularly in professional cycling, 6 with many cyclists undergoing altitude camps (eg, Sierra Nevada, Spain; Teide Volcano, Spain; Tignes, France; Boyacá, Colombia) to prepare for the Grand Tours (ie, Giro d'Italia, Tour de France, and Vuelta Espana) that involve alternating between different hypoxic methods, such as live high-train high or live high-train low, to develop aerobic capacity as a result of increased hemoglobin mass. 7,8 Beyond the well-known variability in responses to hypoxia among athletes, 9 the altitude level of birth and childhood appear as key factors: In a recent study of 33 male professional cyclists, altitude levels influenced anaerobic (30-s and 1-min mean maximal power above 1500 m) and aerobic (5-min; 10-min above 2000 m) performances differently between lowlanders and altitude natives, which might confer a competitive advantage for highlanders at altitudes >1500 m. 6 The highlander professional cyclists come from different locations worldwide (eg, The United States, Ecuador, Colombia, Eritrea), but the Colombian cyclists are the most numerous and have had the best performances during the last decade; that is, several Colombian cyclists have been on the podium in the most important races, including the Vuelta Espana, Giro d'Italia, and Tour de France. ...
Objective: To determine whether the altitude of birth/childhood influences the values in peak power output (PPO) and estimated maximum oxygen uptake (estVO2max) in male Colombian road cyclists of different performance levels. This study also aimed to determine whether cyclists born at high altitudes tend to be more successful. Methods: Eighty riders aged between 17 and 22 years of 3 performance levels (U23 world-class level, WC, n = 8; U23 national level, N23, n = 41; junior national level, J, n = 31) and 3 altitude levels (<800 m, low; 800–2000 m, moderate; >2000 m, high) performed an
ergocycle maximal incremental test to exhaustion at an altitude of 2570 m. Results: Altogether, while cyclists born at an altitude >2000 m represented ∼50% of the analyzed sample, there was a significantly higher proportion (84%) of these cyclists who had participated as professionals in a Grand Tour (χ2[1, N = 80] = 4.58, P < .05). Riders of the low group had lower values of PPO and estVO2max than cyclists of moderate and high altitudes, while no differences were noted between moderate- and high-altitude groups. In N23, PPO and estVO2max were lower in the low- than in the moderate-altitude group, while in the J cyclists, PPO and estVO2max were lower in the low-altitude compared with both moderate- and high-altitude groups. Discussion: Among the cyclists tested at altitude in junior and U23, there is an overrepresentation of individuals who reached an elite level and were born at a high altitude (>2000 m). As no clear differences were observed between moderate- and high-altitude cyclists, the higher prevalence of elite cyclists in the latter group may originate from various—still unclear—mechanisms.
... Indeed, some of the world's most successful endurance athletes have reported multi-year, periodised altitude training camps, spanning over ten years [39,64,72,76]. Altitude training has been recommended to enhance endurance performance in elite athletes [46], provided the evidence-based advice is followed [22,26]. ...
PurposeElite endurance runners frequently utilise live high-train high (LHTH) altitude training to improve endurance performance at sea level (SL). Individual variability in response to the hypoxic exposure have resulted in contradictory findings. In the present case study, changes in total haemoglobin mass (tHbmass) and physiological capacity, in response to 4-weeks of LHTH were documented. We tested if a hypoxic sensitivity test (HST) could predict altitude-induced adaptations to LHTH.Methods
Fifteen elite athletes were selected to complete 4-weeks of LHTH (~ 2400 m). Athletes visited the laboratory for preliminary testing (PRE), to determine lactate threshold (LT), lactate turn point (LTP), maximal oxygen uptake VO2max and tHbmass. During LHTH, athletes completed daily physiological measures [arterial oxygen saturation (SpO2) and body mass] and subjective wellbeing questions. Testing was repeated, for those who completed the full camp, post-LHTH (POST). Additionally, athletes completed the HST prior to LHTH.ResultsA difference (P < 0.05) was found from PRE to POST in average tHbmass (1.8% ± 3.4%), VO2max (2.7% ± 3.4%), LT (6.1% ± 4.6%) and LTP (5.4% ± 3.8%), after 4-weeks LHTH. HST revealed a decrease in oxygen saturation at rest (ΔSpr) and higher hypoxic ventilatory response at rest (HVRr) predicted individual changes tHbmass. Lower hypoxic cardiac response at rest (HCRr) and higher HVRr predicted individual changes VO2max.Conclusion
Four weeks of LHTH at ~ 2400 m increased tHbmass and enhanced physiological capacity in elite endurance runners. There was no observed relationship between these changes and baseline characteristics, pre-LHTH serum ferritin levels, or reported incidents of musculoskeletal injury or illness. The HST did however, estimate changes in tHbmass and VO2max. HST prior to LHTH could allow coaches and practitioners to better inform the acclimatisation strategies and training load application of endurance runners at altitude.
... Altitude training is typically included in the annual training plan as 2-4-week camps at low to moderate altitudes (i.e., ∼ 1,400-2,500 m) (Millet et al., 2010;Mujika et al., 2019). While there are conflicting views on the effects of altitude training on subsequent sea-level performance (Lundby and Robach, 2016;Millet et al., 2019;Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020), there is consensus that acclimatization to altitude is necessary for optimal performance at altitude Burtscher et al., 2018a). Current recommendations suggest that ∼ 14 days of acclimatization at the same altitude as the competition is sufficient at moderate to high altitudes (i.e., 2,000-4,500 m) (Bärtsch et al., 2008;Bergeron et al., 2012;Chapman et al., 2013;Burtscher et al., 2018a). ...
Objective: To monitor the daily variations and time course of changes in selected variables during a 17–21-day altitude training camp at 1,800 m in a group of elite cross-country skiers (9 women, 12 men) and biathletes (7 women, 4 men).
Methods: Among other variables, resting peripheral oxygen saturation (SpO2rest), resting heart rate (HRrest) and urine specific gravity (USG) were monitored daily at altitude, while illness symptoms were monitored weekly. Before and after the camp, body composition (i.e., lean and fat mass) and body mass were assessed in all athletes, while roller-skiing speed at a blood lactate concentration of 4 mmol·L−1 (Speed@4mmol) was assessed in the biathletes only.
Results: Neither SpO2rest, HRrest nor USG changed systematically during the camp (p > 0.05), although some daily time points differed from day one for the latter two variables (p < 0.05). In addition, body composition and body mass were unchanged from before to after the camp (p > 0.05). Eleven out of 15 illness episodes were reported within 4 days of the outbound or homebound flight. The five biathletes who remained free of illness increased their Speed@4mmol by ~ 4% from before to after the camp (p = 0.031).
Conclusions: The present results show that measures typically recommended to monitor acclimatization and responses to altitude in athletes (e.g., SpO2rest and HRrest) did not change systematically over time. Further research is needed to explore the utility of these and other measures in elite endurance athletes at altitudes typical of competition environments
... This clini cal review focuses on the aim of improving sealevel performance through hypoxic training at natural or simulated moderate altitude in highly trained and elite endurance athletes. There is a considerable and growing body of scientific literature on this topic, but the evidence is by no means conclusive [e.g., (19,34)]. Here, we aim to summarize the existing knowledge of altitude training for increasing sealevel perfor mance, to highlight the ambiguities, and to outline guiding principles within the narrow corridors of evidence. ...
Many endurance athletes aim to increase endurance performance at or near sea-level by hypoxic training, which can be realized in natural or artificial altitude via three main concepts: living and training in hypoxia, living in hypoxia and training in normoxia, or living in normoxia and training in hypoxia. The scientific evidence for these concepts is surprisingly unclear, although several ergogenic adaptations to hypoxic training are well described. Hematologic acclimatization through an increase in hemoglobin mass is often considered the most important factor. But hematologic acclimatization does not explain the performance increase found by some studies, indicating other mechanisms and confounders determine successful training adaptation. This clinical review briefly summarizes the current, conflicting knowledge, lists confounders potentially influencing the outcome, and provides some practical guidance to coaches and clinicians for monitoring and optimizing hypoxic training as far as covered by evidence.
... It has been questioned whether altitude training has positive effects on endurance capacity and sea-level performance beyond the effects achieved with similar training performed at sea level. Here, high-quality scientific evidence is limited, and researchers interpret the current scientific data differently [195,196]. Altitude training research is methodologically demanding due to the difficulty of standardizing the intervention, including control groups, and controlling other psychological and physiological confounders during altitude training. Although research provides limited support for a positive effect of altitude training on sea-level performance in endurance sports, these studies remain scarce and underpowered to detect the small adaptations that may be of importance in elite LDR. ...
In this review we integrate the scientific literature and results-proven practice and outline a novel framework for understanding the training and development of elite long-distance performance. Herein, we describe how fundamental training characteristics and well-known training principles are applied. World-leading track runners (i.e., 5000 and 10,000 m) and marathon specialists participate in 9 ± 3 and 6 ± 2 (mean ± SD) annual competitions, respectively. The weekly running distance in the mid-preparation period is in the range 160–220 km for marathoners and 130–190 km for track runners. These differences are mainly explained by more running kilometers on each session for marathon runners. Both groups perform 11–14 sessions per week, and ≥ 80% of the total running volume is performed at low intensity throughout the training year. The training intensity distribution vary across mesocycles and differ between marathon and track runners, but common for both groups is that volume of race-pace running increases as the main competition approaches. The tapering process starts 7–10 days prior to the main competition. While the African runners live and train at high altitude (2000–2500 m above sea level) most of the year, most lowland athletes apply relatively long altitude camps during the preparation period. Overall, this review offers unique insights into the training characteristics of world-class distance runners by integrating scientific literature and results-proven practice, providing a point of departure for future studies related to the training and development in the Olympic long-distance events.
... The live high-train high (LHTH) approach requires prolonged hypobaric exposures, since hemoglobin mass increased by about 1% for every 100 h of altitude exposure at 2200-2500 m (226). LHTH methods are effective, even in elite endurance athletes whose initial blood hemoglobin content exceeds 14 g $ (kg body weight) -1 (87,138). Both LHTH and live high-train low (LHTL) are effective preparations for competitions both at sea level and at high altitude. ...
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.
... Altitude training is an effective method commonly used by elite athletes (Millet and Brocherie, 2020). Prolonged altitude exposure increases erythropoiesis, which is explained by increased plasma erythropoietin concentration (Stray-Gundersen et al., 2001) and leads to an apparent increase in peripheral tissues oxygen delivery. ...
Purpose: This study aimed to investigate the differences between normobaric (NH) and hypobaric hypoxia (HH) on supine heart rate variability (HRV) during a 24-h exposure. We hypothesized a greater decrease in parasympathetic-related parameters in HH than in NH.
Methods: A pooling of original data from forty-one healthy lowland trained men was analyzed. They were exposed to altitude either in NH (F I O 2 = 15.7 ± 2.0%; PB = 698 ± 25 mmHg) or HH (F I O 2 = 20.9%; PB = 534 ± 42 mmHg) in a randomized order. Pulse oximeter oxygen saturation (S p O 2 ), heart rate (HR), and supine HRV were measured during a 7-min rest period three times: before (in normobaric normoxia, NN), after 12 (H12), and 24 h (H24) of either NH or HH exposure. HRV parameters were analyzed for time- and frequency-domains.
Results: S p O 2 was lower in both hypoxic conditions than in NN and was higher in NH than HH at H24. Subjects showed similarly higher HR during both hypoxic conditions than in NN. No difference in HRV parameters was found between NH and HH at any time. The natural logarithm of root mean square of the successive differences (LnRMSSD) and the high frequency spectral power (HF), which reflect parasympathetic activity, decreased similarly in NH and HH when compared to NN.
Conclusion: Despite S p O 2 differences, changes in supine HRV parameters during 24-h exposure were similar between NH and HH conditions indicating a similar decrease in parasympathetic activity. Therefore, HRV can be analyzed similarly in NH and HH conditions.
... (e.g. the "live high-train low" method) . However, there is currently a debate among researchers about whether or not an increased haematological profile translates into enhanced sea-level performance in elite cohorts (Siebenmann and Dempsey 2020; Millet and Brocherie 2020). ...
PurposeThis single-blind, repeated measures study evaluated adaptive and maladaptive responses to continuous and intermittent hypoxic patterns in young adults.Methods
Changes in haematological profile, stress and cardiac damage were measured in ten healthy young participants during three phases: (1) breathing normoxic air (baseline); (2) breathing normoxic air via a mask (Sham-controls); (3) breathing intermittent hypoxia (IH) via a mask, mean peripheral oxygen saturation (SpO2) of 85% ~ 70 min of hypoxia. After a 5-month washout period, participants repeated this three-phase protocol with phase, (4) consisting of continuous hypoxia (CH), mean SpO2 = 85%, ~ 70 min of hypoxia. Measures of the red blood cell count (RBCc), haemoglobin concentration ([Hb]), haematocrit (Hct), percentage of reticulocytes (% Retics), secretory immunoglobulin A (S-IgA), cortisol, cardiac troponin T (cTnT) and the erythropoietic stimulation index (calculated OFF-score) were compared across treatments.ResultsDespite identical hypoxic durations at the same fixed SpO2, no significant effects were observed in either CH or Sham-CH control, compared to baseline. While IH and Sham-IH controls demonstrated significant increases in: RBCc; [Hb]; Hct; and the erythropoietic stimulation index. Notably, the % Retics decreased significantly in response to IH (-31.9%) or Sham-IH control (-23.6%), highlighting the importance of including Sham-controls. No difference was observed in S-IgA, cortisol or cTnT.Conclusion
The IH but not CH pattern significantly increased key adaptive haematological responses, without maladaptive increases in S-IgA, cortisol or cTnT, indicating that the IH hypoxic pattern would be the best method to boost haematological profiles prior to ascent to altitude.
... High-intensity or (repeated-)sprint exercise may induce local tissue hypoxia (with reduced PO 2 ) leading to stabilization of the transcription factor HIF-1α, which increases transcription of genes for capillary growth (Lundby et al., 2009;Egan and Zierath, 2013). Although controversies may exist (e.g., Millet and Brocherie, 2020;Siebenmann and Dempsey, 2020), when performed in hypoxia, high-intensity training also seems effective in increasing transcription of VEGF and Mb (Vogt et al., 2001;Kanatous et al., 2009;Faiss et al., 2013;Brocherie et al., 2018). Importantly, the prolonged low-intensity exercise in polarized training could stimulate muscle protein breakdown via enhanced expression of E3 ligases (Stefanetti et al., 2015), resulting in small muscle fibers that facilitate oxygen diffusion to the mitochondria. ...
In the past decades, researchers have extensively studied (elite) athletes' physiological responses to understand how to maximize their endurance performance. In endurance sports, whole-body measurements such as the maximal oxygen consumption, lactate threshold, and efficiency/economy play a key role in performance. Although these determinants are known to interact, it has also been demonstrated that athletes rarely excel in all three. The leading question is how athletes reach exceptional values in one or all of these determinants to optimize their endurance performance, and how such performance can be explained by (combinations of) underlying physiological determinants. In this review, we advance on Joyner and Coyle's conceptual framework of endurance performance, by integrating a meta-analysis of the interrelationships, and corresponding effect sizes between endurance performance and its key physiological determinants at the macroscopic (whole-body) and the microscopic level (muscle tissue, i.e., muscle fiber oxidative capacity, oxygen supply, muscle fiber size, and fiber type). Moreover, we discuss how these physiological determinants can be improved by training and what potential physiological challenges endurance athletes may face when trying to maximize their performance. This review highlights that integrative assessment of skeletal muscle determinants points toward efficient type-I fibers with a high mitochondrial oxidative capacity and strongly encourages well-adjusted capillarization and myoglobin concentrations to accommodate the required oxygen flux during endurance performance, especially in large muscle fibers. Optimisation of endurance performance requires careful design of training interventions that fine tune modulation of exercise intensity, frequency and duration, and particularly periodisation with respect to the skeletal muscle determinants.
... This training is usually distributed over 2-4 relatively short periods (e.g., ~ 14-18 days) each year, with training at 1500-3000 m, while living at ~ 1800-2000 m [55,63,70]. At the same time, the extent to which altitude training may enhance performance at sea level is widely debated [41,60]. However, the current commentary will primarily discuss training at altitude for optimal acclimatization and performance during competitions at low-to-moderate altitudes (e.g. ...
At the 2022 Winter Olympics in Beijing, the XC skiing, biathlon and nordic combined events will be held at altitudes of ~ 1700 m above sea level, possibly in cold environmental conditions and while requiring adjustment to several time zones. However, the ongoing COVID-19 pandemic may lead to sub-optimal preparations. The current commentary provides the following evidence-based recommendations for the Olympic preparations: make sure to have extensive experience of training (> 60 days annually) and competition at or above the altitude of competition (~ 1700 m), to optimize and individualize your strategies for acclimatization and competition. In preparing for the Olympics, 10–14 days at ~ 1700 m seems to optimize performance at this altitude effectively. An alternative strategy involves two–three weeks of training at > 2000 m, followed by 7–10 days of tapering off at ~ 1700 m. During each of the last 3 or 4 days prior to departure, shift your sleeping and eating schedule by 0.5–1 h towards the time zone in Beijing. In addition, we recommend that you arrive in Beijing one day earlier for each hour change in time zone, followed by appropriate timing of exposure to daylight, meals, social contacts, and naps, in combination with a gradual increase in training load. Optimize your own individual procedures for warming-up, as well as for maintaining body temperature during the period between the warm-up and competition, effective treatment of asthma (if necessary) and pacing at ~ 1700 m with cold ambient temperatures. Although we hope that these recommendations will be helpful in preparing for the Beijing Olympics in 2022, there is a clear need for more solid evidence gained through new sophisticated experiments and observational studies.
... E xercise trainings in real high altitudes or in artificial simulated hypoxic chambers (hypoxic training) are well known as one of the special training strategies for improving various exercise performances, including endurance and repeated exercise performances (Bonetti and Hopkins, 2009;Millet and Brocherie, 2020). These underlying mechanisms remain unknown, the partial oxygen pressure (PO 2 ) is considered to be one of candidates to induce various physiological adaptations by high-altitude and hypoxic exercise training. ...
Takezawa, Toshihiro, Shohei Dobashi, and Katsuhiro Koyama. Cardiorespiratory response and power output during submaximal exercise in normobaric versus hypobaric hypoxia: a pilot study using a specific chamber that controls environmental factors. High Alt Med Biol. 16:000-000, 2021.-Many previous studies have examined hypoxia-induced physiological responses using various conditions, e.g., artificially reduced atmospheric oxygen concentration [normobaric hypoxia (NH) condition] or low barometric pressure at a mountain [hypobaric hypoxia (HH) condition]. However, when comparing the results from these previous studies conducted in artificial NH and HH including real high altitude, we must consider the possibility that environmental factors, such as temperature, humidity, and fraction of inspired carbon dioxide, might affect the physiological responses. Therefore, we examined cardiorespiratory responses and exercise performances during low- to high-intensity exercise at a fixed heart rate (HR) in both NH and HH using a specific chamber where atmospheric oxygen concentration and barometric pressure as well as the abovementioned environmental factors were precisely controlled. Ten well-trained university students (eight males and two females) performed the exercise test consisting of two 20-minute submaximal pedaling at the intensity corresponding to 50% (low) and 70% (high) of their HR reserve, under three conditions [NH (fraction of inspired oxygen, 0.135; barometric pressure, 754 mmHg), HH (fraction of inspired oxygen, 0.209; barometric pressure, 504 mmHg), and normobaric normoxia (NN; fraction of inspired oxygen, 0.209; barometric pressure, 754 mmHg)]. Peripheral oxygen saturation (SpO2) to estimate arterial oxygen saturation and partial pressure of end-tidal carbon dioxide (PETCO2) were monitored throughout the experiment. SpO2, PETCO2, and power output at fixed HRs (i.e., pedaling efficiency) in NH and HH were all significantly lower than those in NN. Moreover, high-intensity exercise in HH induced greater decreases in SpO2 and power output than did high-intensity exercise in NH (NH vs. HH; SpO2, 78.2% ± 5.0% vs. 75.1% ± 7.1%; power output, 120.7 ± 24.9 W vs. 112.4 ± 23.2 W, both p < 0.05). However, high-intensity exercise in HH induced greater increases in PETCO2 than did high-intensity exercise in NH (NH vs. HH; 54.2 ± 5.9 mmHg vs. 57.2 ± 3.4 mmHg, p < 0.01). These results suggest that physiological responses and power output at a fixed HR during hypoxic exposure might depend on the method used to generate the hypoxic condition.
... Recent innovative "live low-train high" methods are now well established for improving repeated-sprint ability in team-sport athletes, 1 but paradoxically the effectiveness of the "most traditional" altitude training methods ("live high-train high" LHTH or "live high-train low" LHTL) in endurance athletes remains a topic highly debated between scientists. 2,3 Among the many points to be further explored in these 2 methods, the mechanisms and time course of postaltitude adaptations (ie, when the athlete returns to sea level) remain under-investigated. [4][5][6] For this period, Chapman et al 6 proposed that the deacclimatization responses of hematological (eg, erythropoietin, plasma volume, hemoglobin mass), ventilatory (eg, ventilation, VO 2 max), and biomechanical/neuromuscular (eg, muscle recruitment, running mechanics) factors would interact to determine the time course of performance capacity in athletes. ...
Aims:
It has been hypothesized that altitude training may alter running mechanics due to several factors such as the slower training velocity with associated alteration in muscle activation and coordination. This would lead to an altered running mechanics attested by an increase in mechanical work for a given intensity and to the need to "re-establish" the neuromuscular coordination and running biomechanics postaltitude. Therefore, the present study aimed to test the hypothesis that "live high-train high" would induce alteration in the running biomechanics (ie, longer contact time, higher vertical oscillations, decreased stiffness, higher external work).
Methods:
Before and 2 to 3 days after 3 weeks of altitude training (1850-2200 m), 9 national-level middle-distance (800-5000 m) male runners performed 2 successive 5-minute bouts of running at moderate intensity on an instrumented treadmill with measured ground reaction forces and gas exchanges. Immediately after the running trials, peak knee extensor torque was assessed during isometric maximal voluntary contraction.
Results:
Except for a slight (-3.0%; P = .04) decrease in vertical stiffness, no mechanical parameters (stride frequency and length, contact and flight times, ground reaction forces, and kinetic and potential work) were modified from prealtitude to postaltitude camp. Running oxygen cost was also unchanged.
Discussion:
The present study is the first one to report that "live high-train high" did not change the main running mechanical parameters, even when measured immediately after the altitude camp. This result has an important practical implication: there is no need for a corrective period at sea level for "normalizing" the running mechanics after an altitude camp.
... In addition to obtaining hematological benefits of altitude acclimatization, one advantage of LHTL is the maintenance of training intensity and oxygen flux comparable to sea level (Levine and Stray-Gundersen 1997). However, despite the widespread use of altitude training among professional athletes, contrasting views exist in the literature regarding LHTL effects on sea-level performance (Millet and Brocherie 2020;Siebenmann and Dempsey, 2020). Because of the natural degradation of the hypoxic adaptations over time (Chapman et al. 2014b), a promising approach would be to include a LHTL training period after a natural altitude sojourn to retain LHTH-induced adaptations. ...
PurposeTo test the hypothesis that hypoxic re-exposure after return from natural altitude training is beneficial in retaining hematological and performance adaptations.Methods
Eighteen mixed martial art fighters completed a 3-weeks natural altitude training camp at 2418 m. Afterwards, participants were randomly assigned to a living high-training low (12 h/d at a simulated altitude of 2800 m) group (LHTL, n = 9) or a living low-training low group (LLTL, n = 9) for a 3-week sea-level training period. At baseline and after return to sea level, hematological [hemoglobin mass (Hbmass) on days 2, 6, 9, 12, 15 and 21] and performance (3000 m time trial and maximal oxygen uptake on days 4, 6, 9, 15 and 21) markers were assessed.ResultsMean Hbmass increased from baseline to day 2 (11.7 ± 0.9 vs. 12.4 ± 1.3 g/kg; + 6.6 ± 7.5%; P < 0.05). While Hbmass remained elevated above baseline in LHTL (P < 0.001), it returned near baseline levels from day 9 in LLTL. Irrespective of groups, mean V̇O2max was only elevated above baseline at day 2 (+ 4.5 ± 0.8%) and day 9 (+ 3.8 ± 8.0%) (both P < 0.05). Compared to baseline, 3000 m running time decreased at day 4 (– 3.1 ± 3.3%; P < 0.05) and day 15 (– 2.8 ± 2.3%; P < 0.05) only.Conclusions
Despite re-exposure to hypoxia allowing a recovery of the hypoxic stimulus to retain Hbmass gains from previous altitude sojourn, there is no performance advantage of this practice above sea level residence. Our results also give support to empirical observations describing alternance of periods of optimal and attenuated performance upon return to sea level.
... In summary, exercise performance in the highly trained athlete during sojourn to what are normally viewed as even "mild" and "moderate" high altitudes is now limited primarily by a pulmonary diffusion capacity, respiratory muscle work and aerobic capacity, neurochemical respiratory control system, and pulmonary vasculature that are underbuilt or excessively sensitive for the combined stresses of hypoxia and high-intensity exercise. In view of these multifaceted negative consequences to endurance performance at high altitude in the athletic sojourner, it appears paradoxical that such large numbers of elite athletes utilize training regimens requiring hypoxic exposure with the intent of enhancing their Hb mass and performance at sea level (131). The efficacy of this practice has recently been questioned (172,184). ...
In the healthy, untrained young adult a case is made for a respiratory system- airways, pulmonary vasculature, lung parenchyma, respiratory muscles and neural ventilatory control system - which is near ideally designed to ensure a highly efficient, homeostatic response to exercise of varying intensities and durations. Our aim was then to consider circumstances in which the intra/extra-thoracic airways, pulmonary vasculature, respiratory muscles and/or blood:gas distribution are underbuilt or inadequately regulated relative to the demands imposed by the cardiovascular system. In these instances, the respiratory system presents a significant limitation to O 2 transport and contributes to the occurrence of locomotor muscle fatigue, inhibition of central locomotor output and exercise performance. Most prominent in these examples of an "underbuilt" respiratory system are highly trained endurance athletes, with additional influences of sex, aging, hypoxic environments and the highly inbred equine. We summarize by evaluating the relative influences of these respiratory system limitations on exercise performance, their impact on pathophysiology and provide recommendations for future investigation.
Background:
Hypoxic and cold environments have been shown to improve the function and performance of athletes. However, it is unclear whether the combination of subalpine conditions and cold temperatures may have a greater effect. The present study aims to investigate the effects of 6 weeks of training in a sub-plateau cold environment on the physical function and athletic ability of elite parallel giant slalom snowboard athletes.
Methods:
Nine elite athletes (four males and five females) participated in the study. The athletes underwent 6 weeks of high intensity ski-specific technical training (150 min/session, six times/week) and medium-intensity physical training (120 min/session, six times/week) prior to the Beijing 2021 Winter Olympic Games test competition. The physiological and biochemical parameters were collected from elbow venous blood samples after each 2-week session to assess the athletes' physical functional status. The athletes' athletic ability was evaluated by measuring their maximal oxygen uptake, Wingate 30 s anaerobic capacity, 30 m sprint run, and race performance. Measurements were taken before and after participating in the training program for six weeks. The repeated measure ANOVA was used to test the overall differences of blood physiological and biochemical indicators. For indicators with significant time main effects, post-hoc tests were conducted using the least significant difference (LSD) method. The paired-samples t-test was used to analyze changes in athletic ability indicators before and after training.
Results:
(1) There was a significant overall time effect for red blood cells (RBC) and white blood cells (WBC) in males; there was also a significant effect on the percentage of lymphocytes (LY%), serum testosterone (T), and testosterone to cortisol ratio (T/C) in females (p < 0.001 - 0.015, η p 2 = 0 . 81 - 0 . 99 ). In addition, a significant time effect was also found for blood urea(BU), serum creatine kinase (CK), and serum cortisol levels in both male and female athletes (p = 0.001 - 0.029, η p 2 = 0 . 52 - 0 . 95 ). (2) BU and CK levels in males and LY% in females were all significantly higher at week 6 (p = 0.001 - 0.038), while WBC in males was significantly lower (p = 0.030). T and T/C were significantly lower in females at week 2 compared to pre-training (p = 0.007, 0.008, respectively), while cortisol (C) was significantly higher in males and females at weeks 2 and 4 (p (male) = 0.015, 0.004, respectively; p (female) = 0.024, 0.030, respectively). (3) There was a noticeable increase in relative maximal oxygen uptake, Wingate 30 s relative average anaerobic power, 30 m sprint run performance, and race performance in comparison to the pre-training measurements (p < 0.001 - 0.027).
Conclusions:
Six weeks of sub-plateau cold environment training may improve physical functioning and promote aerobic and anaerobic capacity for parallel giant slalom snowboard athletes. Furthermore, male athletes had a greater improvement of physical functioning and athletic ability when trained in sub-plateau cold environments.
Objective
To analyze the effect of altitude on hematological and cardiorespiratory variables in adolescent athletes participating in aerobic disciplines.
Methods
21 females and 89 males participated in the study. All were adolescent elite athletes engaged in endurance sports (skating, running and cycling) belonging to two groups: permanent residents in either low altitude (LA, 966 m) or moderate altitude (MA, 2640 m). Hematocrit (Hct), hemoglobin concentration ([Hb]), total hemoglobin mass (Hbt), blood, plasma and erythrocyte volumes (BV, PV and EV), VO2peak and other cardiorespiratory parameters were evaluated.
Results
Sex differences were evident both in LA and HA skating practitioners, the males having higher significant values than the females in oxygen transport-related hematological parameters and VO2peak. The effect of altitude residence was also observed in Hct, [Hb], Hbt and EV with increased (14%–18%) values in the hematological parameters and higher EV (5%–24%). These results matched the significantly higher values of VO2peak measured in MA residents. However, BV and PV did not show differences between LA and MA residents in any case. Sports discipline influenced neither the hematological variables nor most of the cardiorespiratory parameters.
Conclusions
LA and MA adolescent skaters showed sex differences in hematological variables. Endurance-trained male adolescent residents at MA had an increased erythropoietic response and a higher VO2peak compared to their counterparts residing and training at LA. These responses are similar in the three aerobic sports studied, indicating that the variables described are highly sensitive to hypoxia irrespective of the sports discipline.
We aimed to identify potential physiological and performance differences of trained cross-country skiers (V˙o2max=60±4 ml ∙ kg–1 ∙ min–1) following two, 3-week long altitude modalities: 1) training at moderate altitudes (600–1700 m) and living at 1500 m (LMTM;N=8); and 2) training at moderate altitudes (600–1700 m) and living at 1500 m with additional nocturnal normobaric hypoxic exposures (FiO2 =0.17;LHTM; N=8). All participants conducted the same training throughout the altitude training phase and underwent maximal roller ski trials and submaximal cyclo-ergometery before, during and one week after the training camps. No exercise performance or hematological differences were observed between the two modalities. The average roller ski velocities were increased one week after the training camps following both LMTM (p=0.03) and LHTM (p=0.04) with no difference between the two (p=0.68). During the submaximal test, LMTM increased the Tissue Oxygenation Index (11.5±6.5 to 1.0±8.5%; p=0.04), decreased the total hemoglobin concentration (15.1±6.5 to 1.7±12.9 a.u.;p=0.02), and increased blood pH (7.36±0.03 to 7.39±0.03;p=0.03). On the other hand, LHTM augmented minute ventilation (76±14 to 88±10 l·min−1;p=0.04) and systemic blood oxygen saturation by 2±1%; (p=0.02) with no such differences observed following the LMTM. Collectively, despite minor physiological differences observed between the two tested altitude training modalities both induced comparable exercise performance modulation.
Although scientific conclusions remain equivocal, there is evidence-based research, as well as anecdotal support, suggesting that altitude training can enhance performance among Olympic level athletes, particularly in endurance sport. This appears to be due primarily to hypoxia-induced increases in total hemoglobin mass and subsequent improvements in maximal oxygen uptake and other factors contributing to aerobic performance. Although less clear, it is possible that non-hematological adaptations may contribute secondarily to improvements in post-altitude performance. These physiological effects are most likely realized when the altitude exposure is of sufficient “hypoxic dose” to provide the necessary stimuli for performance-affecting changes to occur via hypoxia-inducible factor 1α (HIF-1α) and hypoxia-inducible factor 2α (HIF-2α) pathways and their downstream molecular signaling. Team USA has made a strong commitment over the past 20 years to utilizing altitude training for the enhancement of performance in elite athletes in preparation for the Olympic Games and World Championships. Team USA’s strongest medal-producing Olympic sports—USA Swimming and USA Track and Field—embraced altitude training several years ago, and they continue to be leaders within Team USA in the practical and successful application of altitude training. Whereas USA Swimming utilizes traditional “live high and train high” (LH + TH) altitude training, USA Track and Field tends more toward the use of the altitude training strategy whereby athletes live high (and potentially sleep higher, either naturally or via simulated altitude), while training high during moderate-intensity (< lactate threshold 2) training sessions, and train low during high-intensity (> lactate threshold 2) training sessions (LH + TH[LT]). Although USA Swimming and USA Track and Field have taken different approaches to altitude training, they have been equally successful at the Olympic Games and World Championships, both teams being ranked first in the world based on medals earned in these major international competitions. In addition to USA Swimming and USA Track and Field, several other Team USA sports have had consistently competitive performance results in conjunction with regular and systematic altitude training blocks. The purpose of this paper was to describe select altitude training strategies used by Team USA athletes, and the impact of those strategies on podium performance at major international competitions, specifically the Olympic Games and World Championships.
The aim of the paper was to investigate health aspects of high altitude trekking such as preparation for the physical exertion during trekking at high altitude, the impact of mountaineering on the daily life before and after the expedition, the effect of high-mountain conditions on health and well-being. It was found that in the pre-departure period trekkers commonly train to ensure that they are physically fit for the expedition. They train alone or under the supervision of a trainer. Self-prepared workouts may turn out to be insufficient due to the lack of appropriate training plans. The most challenging aspects of high altitude trekking for the body include carrying too heavy equipment, dealing with illegibly marked routes, wearing inappropriate clothing, having an unbalanced diet, not having enough water, which can lead to dehydration and infections. Misconduct by other people poses a risk. The specific type of effort involved in mountaineering requires balanced nutrition in terms of both micro- and macro-elements. To find the right combination, one has to either experiment or seek advice from a dietitian. However, relatively few people consult a nutrition coach. Among sanitary problems, the most serious one is inappropriate human waste disposal, the resulting lack of drinkable water. Some of the observed problems result from insufficient regulations regarding the conduct in the mountains and from trekkers’ lack of awareness regarding good practices in such extreme conditions.
Han, J, Liu, M, Shi, J, and Li, Y. Construction of a machine learning model to estimate physiological variables of speed skating athletes under hypoxic training conditions. J Strength Cond Res XX(X): 000-000, 2021-Monitoring changes in athletes' physiological variables is essential to create a safe and effective hypoxic training plan for speed skating athletes. This research aims to develop a machine learning estimation model to estimate physiological variables of athletes under hypoxic training conditions based on their physiological measurements collected at sea level. The research team recruited 64 professional speed skating athletes to participate in a 10-week training program, including 3 weeks of sea-level training, followed by 4 weeks of hypoxic training and then a 3-week sea-level recovery period. We measured several physiological variables that could reflect the athletes' oxygen transport capacity in the first 7 weeks, including red blood cell (RBC) count and hemoglobin (Hb) concentration. The physiological variables were measured once a week and then modeled as a mathematical model to estimate measurements' changes using the maximum likelihood method. The mathematical model was then used to construct a machine learning model. Furthermore, the original data (measured once per week) were used to construct a polynomial model using curve fitting. We calculated and compared the mean absolute error between estimated values of the 2 models and measured values. Our results show that the machine learning model estimated RBC count and Hb concentration accurately. The errors of the estimated values were within 5% of the measured values. Compared with the curve fitting polynomial model, the accuracy of the machine learning model in estimating hypoxic training's physiological variables is higher. This study successfully constructed a machine learning model that used physiological variables measured at the sea level to estimate the physiological variables during hypoxic training.
A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat, by examining the benefits of heat acclimation, cooling strategies and hyperhydration. Finally, contemporary controversies are summarized and future research directions provided.
To know the effect that training with acute exposure to hypoxia has on the recovery of the basal heart rate after exercise, to generate a rationalization of acute exposure to hypoxia through the "train up and sleep down" strategy. A total of 4 high performance triathletes participated in this study, the measurements were recorded according to the Heikki Rusko test, the heart rate was recorded through a Polar Fenix 3 heart rate monitor with a band. The study was carried out over a period of one month, recording the training sessions at 70% of the karvonen formukla in the city of. Oaxaca and at the Ixtepeji summit at 3300 m..s.n.m. There was an increase in the mean and range in training with acute exposure to hypoxia, it was confirmed that recovery was more affected at 90 seconds and there are sufficient reasons to consider that it is necessary not to expose to more than 2 sessions a week in the "train above, live below" mode.
TO THE EDITOR: First, we would like to commend the authors of the Viewpoint (2) for this comprehensive summary of factors of importance for running fast marathons. Then, we would like to comment on their discussion of fast marathon physiology (2).
We follow closely the debate concerning 1) footwear de- signed to improve marathon performance; and 2) nonofficial optimization of the course arrangement, ambient conditions, including headwind, individualized starting times, possibilities for hydration, pacing, etc., that influence running performance.
Although marathon performance has improved more than middle-distance running (4 –5% versus 1–2%), does this reflect optimization of such factors and/or improvements in long-term preparation for fast marathons during the last 30 years? De- scriptions of long-, middle- and short-term preparation by current elite marathon runners (1, 2) lack comprehensive anal- ysis of macro- and mesocycles of exercise intensity, volume, frequency, and sequence and individual monitoring and control of internal and external loads.
Our understanding, in particular, of the distribution of train- ing intensity (5) and technology-assisted monitoring among elite athletes has improved (3), and researchers should describe in detail the preparation for and monitoring of fast marathons. This will advance our knowledge concerning intra-individual variations in the fundamental determinants of fast marathons (i.e., maximal oxygen uptake, running economy, etc.). This reporting should provide a holistic overview (4) of the distri- bution of training intensity and volume, frequency of sessions, recovery procedures, the type and characteristics of strength training, environmental conditions (heat and altitude) and poten- tial nutritional strategies associated with the different macro- and mesocycles and tapering utilized by elite male and female mara- thon runners.
TO THE EDITOR: The Viewpoint by Joyner and colleagues (4) on the physiology of fast marathons comes at a timely crossroads in athletics. The authors discuss the physiological limitations pertaining to two of the primary aerobic performance outcome factors, VO2max and lactate threshold. While athletes like Eliud Kipchoge and Brigid Kosgei are arguably near the limits of these physiological parameters, the athletic world has been remarkably naive regarding technological considerations to improve running economy (RE), until very recently. Improvements in RE via footwear have been claimed by athletic companies for quite some time. In 1980, claims of 2.85% improvement in RE were demonstrated with an air cushion in the midsole of marathon shoes versus still-utilized ethylenevinyl acetate (EVA) foams (2). The minimalist footwear trend also distracted the running media, which were hypersensitized to data supporting the improvement of RE with reductions in shoe mass (1). Eventually, the ergogenic effects of cushioning outweighed the once-prevailing thoughts (5), and the search for novel lightweight foams with high rebound had begun. With new applications of polyether block amide (PEBA) foam with carbon fiber plates reported to exhibit resilience of up to 87% (3), it was only a matter of time before athletic performances caught up to the polymer science. Still, there remains a gap in the true effect of high-cushion, high-energy return marathon shoes. Studies typically measure running economy in short duration circumstances; while these data are useful, it may underestimate the true improvements in running economy over the late stages of the marathon distance.
REFERENCES
1. Frederick EC. Physiological and ergonomics factors in running shoe design. Appl Ergon 15: 281–287, 1984. doi:10.1016/0003-6870(84) 90199-6.
2. Frederick EC, Howley ET, Powers SK. Lower O2 cost while running in air-cushion type shoe. Med Sci Sports Exerc 12: 81–82, 1980.
3. Hoogkamer W, Kipp S, Frank JH, Farina EM, Luo G, Kram R. A comparison of the energetic cost of running in marathon racing shoes. Sports Med 48: 1009–1019, 2018. [An Erratum for this article appears in Sports Med 48: 1521–1522, 2018.] doi:10.1007/s40279-017-0811-2.
4. Joyner MJ, Hunter SK, Lucia A, Jones AM. Physiology and fast marathons. J Appl Physiol (1985). doi:10.1152/japplphysiol.00793.2019.
5. Tung KD, Franz JR, Kram R. A test of the metabolic cost of cushioning
hypothesis during unshod and shod running. Med Sci Sports Exerc 46: 324–329, 2014. doi:10.1249/MSS.0b013e3182a63b81.
TO THE EDITOR: Limited evidence is currently available on the influence that genetics exert on athletic performance (1), which may be due to the multifactorial nature of the latter. A recent systematic review including 10,442 participants, of whom 2,984 were elite marathoners, identified 16 singlenucleotide polymorphisms associated with marathon performance (3). There is, however, a lack of replication studies of most of these genes, and thus it is not possible to identify yet the optimum genotype for endurance running performance (1, 3). Further, about half of world-class endurance athletes do not possess the supposedly “optimum” genetic pool (5), which suggests that having the right genetics might favor but not
determine the odds of achieving elite-level performance, possibly due to the key influence of epigenetics.
Although genetics are commonly considered an important factor to break the 2-h marathon barrier, we still do not possess any genetic tool to identify those runners with greater chances of achieving this feat (4). Future multicenter research involving whole genome sequencing, especially in top level marathoners, is needed to identify the performance-enhancing polymorphisms that would allow athletes to break the limits of human performance.
TO THE EDITOR: Joyner et al. (5) in their Viewpoint left no stone unturned in their search for determinants of Kipchoge’s world record. However, they poorly defined the “mechanical efficiency,” which should be clarified since it is a key parameter of running performance.
The minimum, inevitable, work that Kipchoge et al. did to cross the finish line is given by the external frictional drag times the 42.195 km. The overall efficiency can thus be expressed as the ratio between this minimum work and the chemical energy transformed by the muscles (2). It can be also defined as the product of the “muscular efficiency,” indicating the “propulsive efficiency,” indicating the ability to utilize the muscle work to move the body against the wind resistance. While Kipchoge’s recent performance may be partly explained by lower drag due to his body shape and drafting, the recent improvements of running performances are certainly closely related to an enhancement of muscular efficiency. For instance, trained subjects can exploit better the dynamic coupling between segments to save mechanical energy than untrained (1). Additionally, smaller muscle-tendons (and shoes!) hysteresis in athletes (3) reduces the imbalance between energy dissipation and generation, a major determinant of the running cost (4).
Scientific contributions on fatigue resistance, muscle strengthening, and training intensity have potentially led to biochemical and neuromechanical adaptations, improving efficiency. Even a small enhancement of the role played by elasticity may especially impact long-distance performances, by reducing muscular fatigue over a huge number of steps.
REFERENCES
1. Bianchi L, Angelini D, Lacquaniti F. Individual characteristics of human walking mechanics. Pflugers Arch 436: 343–356, 1998. doi:10.1007/ s004240050642.
2. Cavagna GA. Symmetry and asymmetry in bouncing gaits. Symmetry (Basel) 2: 1270–1321, 2010. doi:10.3390/sym2031270.
3. da Rosa RG, Oliveira HB, Gomeñuka NA, Masiero MPB, da Silva ES, Zanardi APJ, de Carvalho AR, Schons P, Peyré-Tartaruga LA. Landing- takeoff asymmetries applied to running mechanics: a new perspective for performance. Front Physiol 10: 415, 2019. doi:10.3389/fphys.2019. 00415.
4. Dewolf AH, Willems PA. Running on a slope: A collision-based analysis to assess the optimal slope. J Biomech 83: 298–304, 2019. doi:10.1016/j. jbiomech.2018.12.024.
5. Joyner MJ, Hunter SK, Lucia A, Jones AM. Physiology and fast marathons. J Appl Physiol (1985). doi:10.1152/japplphysiol.00793.2019.
Accumulating evidence indicates that the brain can play a role to determine
endurance performance, in addition to classical aerobic parameters (2) . For instance,
induction of positive expectations regarding an intervention can improve endurance
performance of well-trained runners without modifying maximal oxygen consumption,
lactate threshold and running economy (5) . Moreover, application of transcranial direct
current stimulation on the left dorsolateral prefrontal cortex enhanced Stroop task
performance (i.e., a measure of inhibitory control) at rest, as well as reduced perceived
effort and improved endurance performance in healthy individuals (1) . Such findings
are possibly explained by a complex brain regulation of endurance performance. Signals
derived from the brain itself (e.g., corollary discharges) and the periphery (e.g., muscle
afferents) are involved in the formation of exercise-related sensations (e.g., pain,
dyspnea, thermal discomfort, perceived effort) (4) . Thus, the ability to cope with such
sensations, which is known as inhibitory control, likely contribute to determine
endurance performance. In this sense, professional cyclists have been shown to present
better inhibitory control at rest as compared to recreational cyclist (3) . However, few
studies have investigated the brain regulation of endurance performance in elite athletes.
Therefore, many questions remain unanswered. For example, does inhibitory control
during exercise indeed play a role to performance regulation? Do African runners
present better inhibitory control than other runners? Is it possible to improve elite
runners’ inhibitory control to further improve performance? Thus, better understanding
and manipulation of brain physiology may give an extra push to elite marathoners
continue improving their marks.
Doi: 10.1152/japplphysiol.00167.2020.
In their Viewpoint, Joyner et al. (2) proposed that a convergence of factors (physiology, training, technology, and logistics) may explain the recent swift improvement in marathon times. While we agree on the importance of these factors and we acknowledge previous research in elite marathon runners, we believe that masters athletes can add to the discussion for reaching fast marathons. The analysis of recent exceptional performances in masters runners (2:27:52 and 2:54:23 at 59 and 70 yr of age, respectively) reveals a common characteristic among these athletes, which is a very high fraction (91–93%) of VO2max at marathon pace (4, 5). In comparison, elite runners generally sustain 80–85%VO2max on the marathon with a quite similar running economy (1, 2). These data show new limits to human physiological capacities during endurance exercise and raise questions about the determinants of performance in the marathon. We may first wonder if the best marathon runners could sustain >90%VO2max on the marathon, and by how much the current record could be improved. We may also wonder if the higher fractional utilization of VO2max observed in masters could derive from the reduction of VO2max with aging or could result from specific long-term training adaptation. Finally, it reopens the debate about the optimization of training for the marathon; should the fractional utilization of VO2max become a priority with advancing age? Within this context, masters athletes require the continued attention of exercise physiologists, and a better knowledge of their training practices could be valuable for improving performance after 40 yr of age (3).
TO THE EDITOR: Over the last three decades, the improvement in
the marathon world record (WR) has been ~4–5% for elite runners (1). During the same time period, marathon performances of the best master runners have improved at a much greater rate, especially for the older age groups (� 60 yr old) (2, 3). When changes in marathon world record performances are considered with advancing age, the decline in performance is ~10% per decade. For example, the marathon WR for a 60-yr-old male is 02:36:30, which represents a running velocity 22% slower than that of the world’s fastest time, set by Eliud Kipchoge (age 34 yr old). However, this trend of agerelated decline in marathon performance is based on WRs that belong to different runners and thus induces bias in the analysis. Previous studies showed that the age-related decline could be limited to 5–7% per decade at least until 60 yr of age for the same well-trained individual (4). Imagine therefore that Kipchoge remains competitive until 60 yr old. If so, we could predict a 6% decline in velocity per decade which would result in a marathon time of 02:18:15 at 60 yr old i.e., 18 min faster than the current WR for a 60-yr-old. This simulation suggests that marathon WRs in master categories will probably continue to improve in the future if ex-elite runners preserve their motivation to compete as they age. These super master runners will therefore offer valuable information about how lifelong endurance exercise can counteract the age-related decline in integrative physiological function (3, 5).
TO THE EDITOR: While the viewpoint (3) superbly summarizes key factors underlining marathon running physiology and potential reasons for recent records surge, the inherently dynamic physiological nature of marathon running might have been understated. To comprehensively interpret marathon performance, one also needs to consider the time-dependent physiological alterations during both, the actual marathon run and the preceding training. In particular, the average elite marathon running velocities can be explained by regression calculations using “static” values of maximal oxygen uptake, lactate threshold (LT) and running economy (RE) (2). However, given the dynamic nature of long-distance running, the contribution of these determinants to subsequent physiological responses and actual running performance significantly varies and cannot be precisely predicted by static values modeling. The variation can relate to both, the relative contribution/importance of each factor and the duration-related dynamic differences. Indeed, LT can be altered due to potential glycogen-depletion related reduction in lactate production while RE is known to decrease as a function of running duration (4). Training also represents a complex dynamical system comprised of numerous fluctuating determinants (i.e. intensity/duration/frequency, hypoxic/heat training, tapering) further complicated by the distinct individual (5) and daily (1) variability in training-induced responses. It, thus, seems crucial to constantly monitor the corresponding training-related physiological fluctuations. Given our currently scarce understanding, further exploration of time-dependent dynamics of physiological determinants during both, the marathon running and training seems warranted. It will provide important insight into the often omitted “dynamic” aspect of the marathon performance puzzle and, ultimately, limits of marathon running.
References
1. Cappaert TA. Time of Day Effect on Athletic Performance: An Update. The Journal of Strength & Conditioning Research 13: 412-421, 1999.
2. Joyner MJ. Modeling: optimal marathon performance on the basis of physiological factors. J Appl Physiol (1985) 70: 683-687, 1991.
3. Joyner MJ, Hunter SK, Lucia A, and Jones AM. Physiology and Fast Marathons. J Appl Physiol (1985) 2020.
4. Lazzer S, Salvadego D, Rejc E, Buglione A, Antonutto G, and di Prampero PE. The energetics of ultra-endurance running. Eur J Appl Physiol 112: 1709-1715, 2012.
5. Ross R, Goodpaster BH, Koch LG, Sarzynski MA, Kohrt WM, Johannsen NM, Skinner JS, Castro A, Irving BA, Noland RC, Sparks LM, Spielmann G, Day AG, Pitsch W, Hopkins WG, and Bouchard C. Precision exercise medicine: understanding exercise response variability. Br J Sports Med 53: 1141-1153, 2019.
TO THE EDITOR: With interest we read the Viewpoint by Joyner
et al. (2) addressing the physiology of fast marathons. In
addition to the prerequisite of a high VO2max, the ability to
sustain a high % of VO2max, and excellent running economy
(2), we consider a role for cerebral oxygenation. A reduction in
cerebral oxygenation has been implicated in the development
of central fatigue as a limitation for exercise performance (4).
Among elite Kenyan (Kalenjin) runners (mean half-marathon
time 62.2 1.0 min), the top performers in a 5-km trial are
those who best maintain their cerebral oxygenation (3). Although a reduced ventilatory drive during exercise would
attenuate reduction in PaCO2 and in turn cerebral blood flow and
oxygenation, Hansen et al. (1) found, by clamping PETCO2
during high-intensity exercise (~90% VO2max), that despite
preventing the hyperventilation-induced reduction in PaCO2 and
the concomitant decrease in cerebral flow velocity, cerebral
oxygenation was reduced at exhaustion. We take reduction in
cerebral oxygenation to indicate that during maximal exercise the cerebral demand exceeds the O2 delivery even under
conditions of maintained cerebral blood flow (1), suggesting
that not only O2 delivery but also the magnitude of cerebral
O2 demand is important for exercise tolerance. It may be
that Kenyan runners due to both excellent genetically endowed mechanical efficiency (2) and training (5) are better
in attenuating the cerebral O2 demand for running and thus
maintain cerebral oxygenation that contributes to the astonishing middle- and long-distance performances in this population (2)
The main determinants of performance during
the marathon are 1) maximal oxygen uptake (VO2max), 2)
ability to sustain high percentages of VO2max during long
periods of time, and 3) running economy (RE). The fractional use of VO2max is related to the ability to sustain high
workloads before lactate begins to accumulate in the blood,
i.e., the so-called lactate threshold (LT). Another important
concept is the critical speed (CS) considered the boundary
between fatigue and performance during endurance exercises. Typically, LT occurs at 75–90% VO2max while CS
occurs at higher absolute and relative intensities. Thus,
physiologically, LT demarcates the transition between moderate- and heavy-intensity domains while CS demarcates the
transition between heavy- and severe-intensity domains.
Consequently, workloads above CS promote an increase in
oxygen consumption, blood lactate accumulation, and a worsening in RE, causing a decrease in performance. In a literature
review, Jones and Vanhatalo showed that elite long-distance runners complete the marathon distance, on average, at
96% of their CS. In this way, considering that currently,
CS is the main landmark for separating the physiological limit
at which physiological homeostasis can be maintained during
prolonged exercises, we believe that CS can be an attractive
tool to guide the prescription of training intensity, as well as
the race-pace strategy for the marathon. Furthermore, future
studies should verify CS as a method to quantify the training
intensity distribution, similar to other studies that used blood
lactate accumulation as a reference.
Purpose:
To analyze if live high-train low (LHTL) effectiveness is improved when daily training is guided by heart rate variability (HRV).
Methods:
Twenty-four elite Nordic skiers took part in a 15-day LHTL study and were randomized into a HRV-guided training hypoxic group (H-HRV, n = 9, sleeping in normobaric hypoxia, FiO2 = 15.0%) and two predefined training groups sleeping either in hypoxia (H, n = 9, FiO2 = 15.0%) or normoxia (N, n = 6). HRV and training loads (TL) were recorded daily. Prior (Pre), one (Post-1), and 21 days (Post-21) following LHTL, athletes performed a 10-km roller-ski test, and a treadmill test for determination of [Formula: see text] was performed at Pre and Post-1.
Results:
Some HRV parameters measured in supine position were different between H-HRV and H: low and high (HF) frequency power in absolute (ms2) (16.0 ± 35.1 vs. 137.0 ± 54.9%, p = 0.05) and normalized units (- 3.8 ± 10.1 vs. 53.0 ± 19.5%, p = 0.02), HF(nu) (6.3 ± 6.8 vs. - 13.7 ± 8.0%, p = 0.03) as well as heart rate (3.7 ± 6.3 vs. 12.3 ± 4.1%, p = 0.008). At Post-1, [Formula: see text] was improved in H-HRV and H (3.8 ± 3.1%; p = 0.02 vs. 3.0 ± 4.4%; p = 0.08) but not in N (0.9 ± 5.1%; p = 0.7). Only H-HRV improved the roller-ski performance at Post-21 (- 2.7 ± 3.6%, p = 0.05).
Conclusion:
The daily individualization of TL reduced the decrease in autonomic nervous system parasympathetic activity commonly associated with LHTL. The improved performance and oxygen consumption in the two LHTL groups confirm the effectiveness of LHTL even in elite endurance athletes.
Constantini, Keren, Daniel P. Wilhite, and Robert F. Chapman. A clinician guide to altitude training for optimal endurance exercise performance at sea level. High Alt Med Biol 00:000-000, 2017.-For well over 50 years, endurance athletes have been utilizing altitude training in an effort to enhance performance in sea level competition. This brief review will offer the clinician a series of evidence-based best-practice guidelines on prealtitude and altitude training considerations, which can ultimately maximize performance improvement outcomes.
Many sport competitions, typically involving the completion of single- (e.g. track-and-field or track cycling events) and multiple-sprint exercises (e.g. team and racquet sports, cycling races), are staged at terrestrial altitudes ranging from 1000 to 2500 m. Our aim was to comprehensively review the current knowledge on the responses to either acute or chronic altitude exposure relevant to single and multiple sprints. Performance of a single sprint is generally not negatively affected by acute exposure to simulated altitude (i.e. normobaric hypoxia) because an enhanced anaerobic energy release compensates for the reduced aerobic adenosine triphosphate production. Conversely, the reduction in air density in terrestrial altitude (i.e. hypobaric hypoxia) leads to an improved sprinting performance when aerodynamic drag is a limiting factor. With the repetition of maximal efforts, however, repeated-sprint ability is more altered (i.e. with earlier and larger performance decrements) at high altitudes (>3000–3600 m or inspired fraction of oxygen <14.4–13.3%) compared with either normoxia or low-to-moderate altitudes (<3000 m or inspired fraction of oxygen >14.4%). Traditionally, altitude training camps involve chronic exposure to low-to-moderate terrestrial altitudes (<3000 m or inspired fraction of oxygen >14.4%) for inducing haematological adaptations. However, beneficial effects on sprint performance after such altitude interventions are still debated. Recently, innovative ‘live low-train high’ methods, in isolation or in combination with hypoxic residence, have emerged with the belief that up-regulated non-haematological peripheral adaptations may further improve performance of multiple sprints compared with similar normoxic interventions.
Background
Repeated-sprint training in hypoxia (RSH) is a recent intervention regarding which numerous studies have reported effects on sea-level physical performance outcomes that are debated. No previous study has performed a meta-analysis of the effects of RSH. Objective
We systematically reviewed the literature and meta-analyzed the effects of RSH versus repeated-sprint training in normoxia (RSN) on key components of sea-level physical performance, i.e., best and mean (all sprint) performance during repeated-sprint exercise and aerobic capacity (i.e., maximal oxygen uptake [\(\dot{V}{\text{O}}_{2\hbox{max} }\)]). Methods
The PubMed/MEDLINE, SportDiscus®, ProQuest, and Web of Science online databases were searched for original articles—published up to July 2016—assessing changes in physical performance following RSH and RSN. The meta-analysis was conducted to determine the standardized mean difference (SMD) between the effects of RSH and RSN on sea-level performance outcomes. ResultsAfter systematic review, nine controlled studies were selected, including a total of 202 individuals (mean age 22.6 ± 6.1 years; 180 males). After data pooling, mean performance during repeated sprints (SMD = 0.46, 95% confidence interval [CI] −0.02 to 0.93; P = 0.05) was further enhanced with RSH when compared with RSN. Although non-significant, additional benefits were also observed for best repeated-sprint performance (SMD = 0.31, 95% CI −0.03 to 0.89; P = 0.30) and \(\dot{V}{\text{O}}_{2\hbox{max} }\) (SMD = 0.18, 95% CI −0.25 to 0.61; P = 0.41). Conclusion
Based on current scientific literature, RSH induces greater improvement for mean repeated-sprint performance during sea-level repeated sprinting than RSN. The additional benefit observed for best repeated-sprint performance and \(\dot{V}{\text{O}}_{2\hbox{max} }\) for RSH versus RSN was not significantly different.
Saugy, Jonas J., Laurent Schmitt, Sibylle Fallet, Raphael Faiss, Jean-Marc Vesin, Mattia Bertschi, Raphael Heinzer, and Gregoire P. Millet. Sleep disordered breathing during live high-train low in normobaric versus hypobaric hypoxia. High Alt Med Biol. 16:000-000, 2016.-The present study aimed to compare sleep disordered breathing during live high-train low (LHTL) altitude camp using normobaric hypoxia (NH) and hypobaric hypoxia (HH). Sixteen highly trained triathletes completed two 18-day LHTL camps in a crossover designed study. They trained at 1100-1200 m while they slept either in NH at a simulated altitude of 2250 m or in HH. Breathing frequency and oxygen saturation (SpO2) were recorded continuously during all nights and oxygen desaturation index (ODI 3%) calculated. Breathing frequency was lower for NH than HH during the camps (14.6 +/- 3.1 breath x min-1 vs. 17.2 +/- 3.4 breath x min-1, p < 0.001). SpO2 was lower for HH than NH (90.8 +/- 0.3 vs. 91.9 +/- 0.2, p < 0.001) and ODI 3% was higher for HH than NH (15.1 +/- 3.5 vs. 9.9 +/- 1.6, p < 0.001). Sleep in moderate HH is more altered than in NH during a LHTL camp.
Fore more than a decade, the live high–train low (LHTL) approach, developed by Levine and Stray-Gundersen, has been widely used by elite endurance athletes. Originally, it was pointed out, that by living at moderate altitude, athletes should benefit from an increased red cell volume (RCV) and hemoglobin mass (Hbmass), while the training at low altitudes should prevent the disadvantage of reduced training intensity at moderate altitude. VO2max is reduced linearly by about 6–8 % per 1000 m increasing altitude in elite athletes from sea level to 3000 m, with corresponding higher relative training intensities for the same absolute work load. With 2 weeks of acclimatization, this initial deficit can be reduced by about one half. It has been debated during the last years whether sea-level training or exposure to moderate altitude increases RCV and Hbmass in elite endurance athletes. Studies which directly measured Hbmass with the optimized CO-rebreathing technique demonstrated that Hbmass in endurance athletes is not influenced by sea-level training. We documented that Hbmass is not increased after 3 years of training in national team cross-country skiers. When athletes are exposed to moderate altitude, new studies support the argument that it is possible to increase Hbmass temporarily by 5–6 %, provided that athletes spend >400 h at altitudes above 2300–2500 m. However, this effect size is smaller than the reported 10–14 % higher Hbmass values of endurance athletes living permanently at 2600 m. It remains to be investigated whether endurance athletes reach these values with a series of LHTL camps.
This study determined the effect of repeated sprint training in hypoxia (RSH) in female athletes.
Thirty-two college female athletes performed repeated cycling sprints of two sets of 10 × 7-s sprints with a 30-s rest between sprints twice per week for 4 weeks under either normoxic conditions (RSN group; FiO2, 20.9%; n = 16) or hypoxic conditions (RSH group; FiO2, 14.5%; n = 16). The repeated sprint ability (10 × 7-s sprints) and maximal oxygen uptake ([Formula: see text]) were determined before and after the training period.
After training, when compared to pre-values, the mean power output was higher in all sprints during the repeated sprint test in the RSH group but only for the second half of the sprints in the RSN group (P ≤ 0.05). The percentage increases in peak and mean power output between before and after the training period were significantly greater in the RSH group than in the RSN group (peak power output, 5.0 ± 0.7% vs. 1.5 ± 0.9%, respectively; mean power output, 9.7 ± 0.9% vs. 6.0 ± 0.8%, respectively; P < 0.05). [Formula: see text] did not change significantly after the training period in either group.
Four weeks of RSH further enhanced the peak and mean power output during repeated sprint test compared with RSN.
We address adaptive vs. maladaptive responses to hypoxemia in healthy humans and hypoxic-tolerant species during wakefulness, sleep, and exercise. Types of hypoxemia discussed include short-term and life-long residence at high altitudes, the intermittent hypoxemia attending sleep apnea, or training regimens prescribed for endurance athletes. We propose that hypoxia presents an insult to O2 transport, which is poorly tolerated in most humans because of the physiological cost.
©2015 Int. Union Physiol. Sci./Am. Physiol. Soc.
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.
High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally-trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV estimated by carbon monoxide re-breathing at SL, on every fourth day at HA, and one and two weeks upon return to SL. Four weeks at HA increased Hbmass by 5.26 % (range 2.5 - 11.1 %; p<0.001). The individual Hbmass increases commenced with up to 12 days delay and reached a maximal rate of 4.04 ± 1.02 g.d(-1) after 14.9 ± 5.2 days. The probability for Hbmass to plateau increased steeply after 20-24 days. Upon return to SL Hbmass decayed by -2.46 ± 2.3 g.d(-1), reaching values similar to baseline after two weeks. PV, aldosterone concentration and renin activity were reduced at HA (p<0.001) while the total circulating protein mass remained unaffected. In summary the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ~3 weeks. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data supports that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure.
Copyright © 2014, Journal of Applied Physiology.
Introduction:
This controlled, nonrandomized, parallel-groups trial investigated the effects on performance, V˙O2 and hemoglobin mass (tHbmass) of four preparatory in-season training interventions: living and training at moderate altitude for 3 and 4 wk (Hi-Hi3, Hi-Hi), living high and training high and low (Hi-HiLo, 4 wk), and living and training at sea level (SL) (Lo-Lo, 4 wk).
Methods:
From 61 elite swimmers, 54 met all inclusion criteria and completed time trials over 50- and 400-m crawl (TT50, TT400), and 100 (sprinters) or 200 m (nonsprinters) at best stroke (TT100/TT200). Maximal oxygen uptake (V˙O2max) and HR were measured with an incremental 4 × 200 m test. Training load was estimated using cumulative training impulse method and session RPE. Initial measures (PRE) were repeated immediately (POST) and once weekly on return to SL (PostW1 to PostW4). tHbmass was measured in duplicate at PRE and once weekly during the camp with CO rebreathing. Effects were analyzed using mixed linear modeling.
Results:
TT100 or TT200 was worse or unchanged immediately at POST, but improved by approximately 3.5% regardless of living or training at SL or altitude after at least 1 wk of SL recovery. Hi-HiLo achieved greater improvement 2 (5.3%) and 4 wk (6.3%) after the camp. Hi-HiLo also improved more in TT400 and TT50 2 (4.2% and 5.2%, respectively) and 4 wk (4.7% and 5.5%) from return. This performance improvement was not linked linearly to changes in V˙O2max or tHbmass.
Conclusions:
A well-implemented 3- or 4-wk training camp may impair performance immediately but clearly improves performance even in elite swimmers after a period of SL recovery. Hi-HiLo for 4 wk improves performance in swimming above and beyond altitude and SL controls through complex mechanisms involving altitude living and SL training effects.
In 2007, Wilber1 presented the main altitude/hypoxic training methods used by elite athletes: ‘live high—train high’ (LHTH) and ‘live high—train low’ (LHTL); sleeping at altitude to gain the haematological adaptations (increased erythrocyte volume) but training at sea level to maximise performance (maintenance of sea-level training intensity and oxygen flux). The LHTL method can be accomplished through a number of methods and devices: natural/terrestrial altitude, nitrogen dilution, oxygen filtration and supplemental oxygen. Another method is the ‘live low—train high’ (LLTH) method including intermittent hypoxic exposure at rest (IHE) or during intermittent hypoxic training sessions (IHT). Noteworthy, all supporting references were conducted with endurance elite athletes (ie, cyclists, triathletes, cross-country skiers, runners, swimmers, kayakers and rowers) and there is an extensive literature relative to LHTH as well as LHTL. However, there is a lack of evidence for the applicability of these methods in team-sport athletes.
In recent times, media reports have provided us with coverage of some high-profile clubs or national squads in various team-sport disciplines undertaking fitness programmes at altitude during the early preseason or in preparation of a major competition. Despite the evident observation that athletes from different team sports and from all around the world are using altitude training more than ever before, it is …
Over the past two decades, intermittent hypoxic training (IHT), that is, a method where athletes live at or near sea level but train under hypoxic conditions, has gained unprecedented popularity. By adding the stress of hypoxia during 'aerobic' or 'anaerobic' interval training, it is believed that IHT would potentiate greater performance improvements compared to similar training at sea level. A thorough analysis of studies including IHT, however, leads to strikingly poor benefits for sea-level performance improvement, compared to the same training method performed in normoxia. Despite the positive molecular adaptations observed after various IHT modalities, the characteristics of optimal training stimulus in hypoxia are still unclear and their functional translation in terms of whole-body performance enhancement is minimal. To overcome some of the inherent limitations of IHT (lower training stimulus due to hypoxia), recent studies have successfully investigated a new training method based on the repetition of short (<30 s) 'all-out' sprints with incomplete recoveries in hypoxia, the so-called repeated sprint training in hypoxia (RSH). The aims of the present review are therefore threefold: first, to summarise the main mechanisms for interval training and repeated sprint training in normoxia. Second, to critically analyse the results of the studies involving high-intensity exercises performed in hypoxia for sea-level performance enhancement by differentiating IHT and RSH. Third, to discuss the potential mechanisms underpinning the effectiveness of those methods, and their inherent limitations, along with the new research avenues surrounding this topic.
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 .
A 45-year-old healthy man wishes to climb Mount Kilimanjaro (5895 m) in a 5-day period, starting at 1800 m. The results of a recent exercise stress test were normal; he runs 10 km 4 or 5 times per week and finished a marathon in less than 4 hours last year. He wants to know how he can prevent becoming ill at high altitude and whether training or sleeping under normobaric hypoxic conditions in the weeks before the ascent would be helpful. What would you advise?
While intermittent hypoxic training (IHT) has been reported to evoke cellular responses via hypoxia inducible factors (HIFs) but without substantial performance benefits in endurance athletes, we hypothesized that repeated sprint training in hypoxia could enhance repeated sprint ability (RSA) performed in normoxia via improved glycolysis and O(2) utilization. 40 trained subjects completed 8 cycling repeated sprint sessions in hypoxia (RSH, 3000 m) or normoxia (RSN, 485 m). Before (Pre-) and after (Post-) training, muscular levels of selected mRNAs were analyzed from resting muscle biopsies and RSA tested until exhaustion (10-s sprint, work-to-rest ratio 1∶2) with muscle perfusion assessed by near-infrared spectroscopy. From Pre- to Post-, the average power output of all sprints in RSA was increased (p<0.01) to the same extent (6% vs 7%, NS) in RSH and in RSN but the number of sprints to exhaustion was increased in RSH (9.4±4.8 vs. 13.0±6.2 sprints, p<0.01) but not in RSN (9.3±4.2 vs. 8.9±3.5). mRNA concentrations of HIF-1α (+55%), carbonic anhydrase III (+35%) and monocarboxylate transporter-4 (+20%) were augmented (p<0.05) whereas mitochondrial transcription factor A (-40%), peroxisome proliferator-activated receptor gamma coactivator 1α (-23%) and monocarboxylate transporter-1 (-36%) were decreased (p<0.01) in RSH only. Besides, the changes in total hemoglobin variations (Δ[tHb]) during sprints throughout RSA test increased to a greater extent (p<0.01) in RSH. Our findings show larger improvement in repeated sprint performance in RSH than in RSN with significant molecular adaptations and larger blood perfusion variations in active muscles.
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.
to the editor: Siebenmann and colleagues ([13][1]) found that 4 wk of simulated altitude (16 hr/day, 3,000 m) failed to increase Hbmass. We believe their methodology to quantify Hbmass was suboptimal, which confounds interpretation.
In the mid-1990s, Finnish scientists reported increased red cell
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.
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.
Elite distance runners participated in one of two studies designed to investigate the effects of moderate altitude training (inspiratory partial pressure of oxygen approximately 115-125 mmHg) on submaximal, maximal and supramaximal exercise performance following return to sea-level. Study 1 (New Mexico, USA) involved 14 subjects who were assigned to a 4-week altitude training camp (1500-2000 m) whilst 9 performance-matched subjects continued with an identical training programme at sea-level (CON). Ten EXP subjects who trained at 1640 m and 19 CON subjects also participated in study 2 (Krugersdorp, South Africa). Selected metabolic and cardiorespiratory parameters were determined with the subjects at rest and during exercise 21 days prior to (PRE) and 10 and 20 days following their return to sea-level (POST). Whole blood lactate decreased by 23% (P < 0.05 vs PRE) during submaximal exercise in the EXP group only after 20 days at sea-level (study 1). However, the lactate threshold and other measures of running economy remained unchanged. Similarly, supramaximal performance during a standardised track session did not change. Study 2 demonstrated that hypoxia per se did not alter performance. In contrast, in the EXP group supramaximal running velocity decreased by 2% (P < 0.05) after 20 days at sea-level. Both studies were characterised by a 50% increase in the frequency of upper respiratory and gastrointestinal tract infections during the altitude sojourns, and two male subjects were diagnosed with infectious mononucleosis following their return to sea-level (study 1). Group mean plasma glutamine concentrations at rest decreased by 19% or 143 (74) microM (P < 0.001) after 3 weeks at altitude, which may have been implicated in the increased incidence of infectious illness.
The efficiency of "living high, training low" (LHTL) remains controversial, despite its wide utilization. This study aimed to verify whether maximal and/or submaximal aerobic performance were modified by LHTL and whether these effects persist for 15 days after returning to normoxia. Last, we tried to elucidate whether the mechanisms involved were only related to changes in oxygen-carrying capacity. Eleven elite middle-distance runners were tested before (Pre), at the end (Post1), and 15 days after the end (Post2) of an 18-day LHTL session. Hypoxic group (LHTL, n = 5) spent 14 h/day in hypoxia (6 nights at 2,500 m and 12 nights at 3,000 m), whereas the control group (CON, n = 6) slept in normoxia (1,200 m). Both LHTL and CON trained at 1,200 m. Maximal oxygen uptake and maximal aerobic power were improved at Post1 and Post2 for LHTL only (+7.1 and +3.4% for maximal oxygen uptake, +8.4 and +4.7% for maximal aerobic power, respectively). Similarly oxygen uptake and ventilation at ventilatory threshold increased in LHTL only (+18.1 and +12.2% at Post1, +15.9 and +15.4% at Post2, respectively). Heart rate during a 10-min run at 19.5 km/h decreased for LHTL at Post2 (-4.4%). Despite the stimulation of erythropoiesis in LHTL shown by the 27.4% increase in serum transferrin receptor and the 10.1% increase in total hemoglobin mass, red cell volume was not significantly increased at Post1 (+9.2%, not significant). Therefore, both maximal and submaximal aerobic performance in elite runners were increased by LHTL mainly linked to an improvement in oxygen transport in early return to normoxia and probably to other process at Post2.