Randomized controlled trial of intermittent hypoxia in Parkinson's disease: study rationale and protocol

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disease for which no disease-modifying therapies exist. Preclinical and clinical evidence suggest that repeated exposure to intermittent hypoxia might have short- and long-term benefits in PD. In a previous exploratory phase I trial, we demonstrated that in-clinic intermittent hypoxia exposure is safe and feasible with short-term symptomatic effects on PD symptoms. The current study aims to explore the safety, tolerability, feasibility, and net symptomatic effects of a four-week intermittent hypoxia protocol, administered at home, in individuals with PD.

METHODS/DESIGN

This is a two-armed double-blinded randomized controlled trial involving 40 individuals with mild to moderate PD. Participants will receive 45 min of normobaric intermittent hypoxia (fraction of inspired oxygen 0.16 for 5 min interspersed with 5 min normoxia), 3 times a week for 4 weeks. Co-primary endpoints include nature and total number of adverse events, and a feasibility-tolerability questionnaire. Secondary endpoints include Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part II and III scores, gait tests and biomarkers indicative of hypoxic dose and neuroprotective pathway induction.

DISCUSSION

This trial builds on the previous phase I trial and aims to investigate the safety, tolerability, feasibility, and net symptomatic effects of intermittent hypoxia in individuals with PD. Additionally, the study aims to explore induction of relevant neuroprotective pathways as measured in plasma. The results of this trial could provide further insight into the potential of hypoxia-based therapy as a novel treatment approach for PD.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05948761 (registered June 20th, 2023).

Recommendations for Women in Mountain Sports and Hypoxia Training/Conditioning

The (patho-)physiological responses to hypoxia are highly heterogeneous between individuals. In this review, we focused on the roles of sex differences, which emerge as important factors in the regulation of the body's reaction to hypoxia. Several aspects should be considered for future research on hypoxia-related sex differences, particularly altitude training and clinical applications of hypoxia, as these will affect the selection of the optimal dose regarding safety and efficiency. There are several implications, but there are no practical recommendations if/how women should behave differently from men to optimise the benefits or minimise the risks of these hypoxia-related practices. Here, we evaluate the scarce scientific evidence of distinct (patho)physiological responses and adaptations to high altitude/hypoxia, biomechanical/anatomical differences in uphill/downhill locomotion, which is highly relevant for exercising in mountainous environments, and potentially differential effects of altitude training in women. Based on these factors, we derive sex-specific recommendations for mountain sports and intermittent hypoxia conditioning: (1) Although higher vulnerabilities of women to acute mountain sickness have not been unambiguously shown, sex-dependent physiological reactions to hypoxia may contribute to an increased acute mountain sickness vulnerability in some women. Adequate acclimatisation, slow ascent speed and/or preventive medication (e.g. acetazolamide) are solutions. (2) Targeted training of the respiratory musculature could be a valuable preparation for altitude training in women. (3) Sex hormones influence hypoxia responses and hormonal-cycle and/or menstrual-cycle phases therefore may be factors in acclimatisation to altitude and efficiency of altitude training. As many of the recommendations or observations of the present work remain partly speculative, we join previous calls for further quality research on female athletes in sports to be extended to the field of altitude and hypoxia.

Effects of three weeks base training at moderate simulated altitude with or without hypoxic residence on exercise capacity and physiological adaptations in well-trained male runners

Objectives

To test the hypothesis that 'live high-base train high-interval train low' (HiHiLo) altitude training, compared to 'live low-train high' (LoHi), yields greater benefits on performance and physiological adaptations.

Methods

Sixteen young male middle-distance runners (age, 17.0 ± 1.5 y; body mass, 58.8 ± 4.9 kg; body height, 176.3 ± 4.3 cm; training years, 3-5 y; training distance per week, 30-60 km.wk-1) with a peak oxygen uptake averaging ~65 ml.min-1.kg-1 trained in a normobaric hypoxia chamber (simulated altitude of ~2,500 m, monitored by heart rate ~170 bpm; thrice weekly) for 3 weeks. During this period, the HiHiLo group (n = 8) stayed in normobaric hypoxia (at ~2,800 m; 10 h.day-1), while the LoHi group (n = 8) resided near sea level. Before and immediately after the intervention, peak oxygen uptake and exercise-induced arterial hypoxemia responses (incremental cycle test) as well as running performance and time-domain heart rate variability (5-km time trial) were assessed. Hematological variables were monitored at baseline and on days 1, 7, 14 and 21 during the intervention.

Results

Peak oxygen uptake and running performance did not differ before and after the intervention in either group (all P > 0.05). Exercise-induced arterial hypoxemia responses, measured both at submaximal (240 W) and maximal loads during the incremental test, and log-transformed root mean square of successive R-R intervals during the 4-min post-run recovery period, did not change (all P > 0.05). Hematocrit, mean reticulocyte absolute count and reticulocyte percentage increased above baseline levels on day 21 of the intervention (all P < 0.001), irrespective of group.

Conclusions

Well-trained runners undertaking base training at moderate simulated altitude for 3 weeks, with or without hypoxic residence, showed no performance improvement, also with unchanged time-domain heart rate variability and exercise-induced arterial hypoxemia responses.

The Hypoxia Response Pathway: A Potential Intervention Target in Parkinson's Disease?

Parkinson's disease (PD) is a progressive neurodegenerative disorder for which only symptomatic treatments are available. Both preclinical and clinical studies suggest that moderate hypoxia induces evolutionarily conserved adaptive mechanisms that enhance neuronal viability and survival. Therefore, targeting the hypoxia response pathway might provide neuroprotection by ameliorating the deleterious effects of mitochondrial dysfunction and oxidative stress, which underlie neurodegeneration in PD. Here, we review experimental studies regarding the link between PD pathophysiology and neurophysiological adaptations to hypoxia. We highlight the mechanistic differences between the rescuing effects of chronic hypoxia in neurodegeneration and short-term moderate hypoxia to improve neuronal resilience, termed "hypoxic conditioning". Moreover, we interpret these preclinical observations regarding the pharmacological targeting of the hypoxia response pathway. Finally, we discuss controversies with respect to the differential effects of hypoxia response pathway activation across the PD spectrum, as well as intervention dosing in hypoxic conditioning and potential harmful effects of such interventions. We recommend that initial clinical studies in PD should focus on the safety, physiological responses, and mechanisms of hypoxic conditioning, as well as on repurposing of existing pharmacological compounds. © 2023 International Parkinson and Movement Disorder Society.

Potential for using simulated altitude as a means of prehabilitation: a physiology study

The current pandemic of surgical complications necessitates urgent and pragmatic innovation to reduce postoperative morbidity and mortality, which are associated with poor pre-operative fitness and anaemia. Exercise prehabilitation is a compelling strategy, but it has proven difficult to establish that it improves outcomes either in isolation or as part of a multimodal approach. Simulated altitude exposure improves performance in athletes and offers a novel potential means of improving cardiorespiratory and metabolic fitness and alleviating anaemia within the prehabilitation window. We aimed to provide an initial physiological foundation for 'altitude prehabilitation' by determining the physiological effects of one week of simulated altitude (FI O2 15%, equivalent to approximately 2438 m (8000 ft)) in older sedentary volunteers. The study used a randomised, double-blind, sham-controlled crossover design. Eight participants spent counterbalanced normoxic and hypoxic weeks in a residential hypoxia facility and underwent repeated cardiopulmonary exercise tests. Mean (SD) age of participants was 64 (7) y and they were unfit, with mean (SD) baseline anaerobic threshold 12 (2) ml.kg-1 .min-1 and mean (SD) peak V̇O2 15 (3) ml.kg-1 .min-1 . Hypoxia was mild (mean (SD) Sp O2 93 (2) %, p < 0.001) and well-tolerated. Despite some indication of greater peak exercise capacity following hypoxia, overall there was no effect of simulated altitude on anaerobic threshold or peak V̇O2 . However, hypoxia induced a substantial increase in mean (SD) haemoglobin of 1.5 (2.7) g.dl-1 (13% increase, p = 0.028). This study has established the concept and feasibility of 'altitude prehabilitation' and demonstrated specific potential for improving haematological fitness. Physiologically, there is value in exploring a possible role for simulated altitude in pre-operative optimisation.

Physiological and performance effects of live high train low altitude training for elite endurance athletes: A narrative review

Altitude training has become an important training application for athletes due its potential for altering physiology and enhancing performance. This practice is commonly used by athletes, with a popular choice being the live high - train low approach. This model recommends that athletes live at high altitude (1250-3000 m), but train at low altitude or sea-level (0-1200 m). Exposure to altitude often leads to hypoxic stress and in turn stimulates changes in total haemoglobin mass, erythropoietin, and soluble transferrin receptors, which alter further underlying physiology. Through enhanced physiology, improved exercise performance may arise through enhancement of the oxygen transport system which is important for endurance events. Previous investigations into the effects of altitude training on exercise performance have been completed in a range of contexts, including running, cycling, swimming, and triathlon. Often following a LHTL altitude intervention, athletes realise improvements in maximal oxygen consumption capacity, time trial performance and peak power outputs. Although heterogeneity exists among LHTL methodologies, i.e., exposure durations and altitude ranges, we synthesised this data into kilometre hours, and found that the most common hypoxic doses used in LHTL interventions ranged from ∼578-687 km h. As this narrative review demonstrates, there are potential advantages to using altitude training to enhance physiology and improve performance for endurance athletes.

Comparative efficacy of various hypoxic training paradigms on maximal oxygen consumption: A systematic review and network meta-analysis

Background

Enhancement in maximal oxygen consumption (VO2max) induced by hypoxic training is important for both athletes and non-athletes. However, the lack of comparison of multiple paradigms and the exploration of related modulating factors leads to the inability to recommend the optimal regimen in different situations. This study aimed to investigate the efficacy of seven common hypoxic training paradigms on VO2max and associated moderators.

Methods

Electronic (i.e., five databases) and manual searches were performed, and 42 studies involving 1246 healthy adults were included. Pairwise meta-analyses were conducted to compare different hypoxic training paradigms and hypoxic training and control conditions. The Bayesian network meta-analysis model was applied to calculate the standardised mean differences (SMDs) of pre-post VO2max alteration among hypoxic training paradigms in overall, athlete, and non-athlete populations, while meta-regression analyses were employed to explore the relationships between covariates and SMDs.

Results

All seven hypoxic training paradigms were effective to varying degrees, with SMDs ranging from 1.45 to 7.10. Intermittent hypoxia interval training (IHIT) had the highest probability of being the most efficient hypoxic training paradigm in the overall population and athlete subgroup (42%, 44%), whereas intermittent hypoxic training (IHT) was the most promising hypoxic training paradigm among non-athletes (66%). Meta-regression analysis revealed that saturation hours (coefficient, 0.004; P = 0.038; 95% CI [0.0002, 0.0085]) accounted for variations of VO2max improvement induced by IHT.

Conclusion

Efficient hypoxic training paradigms for VO2max gains differed between athletes and non-athletes, with IHIT ranking best for athletes and IHT for non-athletes. The practicability of saturation hours is confirmed with respect to dose-response issues in the future hypoxic training and associated scientific research.

Registration

This study was registered in the PROSPERO international prospective register of systematic reviews (CRD42022333548).

Optimal type and dose of hypoxic training for improving maximal aerobic capacity in athletes: a systematic review and Bayesian model-based network meta-analysis

Objective: This study aimed to compare and rank the effect of hypoxic practices on maximum oxygen consumption (VO2max) 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 VO2max 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 VO2max 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 VO2max of athletes. According to the P-scores, LHTL combined with low altitude training was the most effective intervention for improving VO2max (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.

"Living High-Training Low" for Olympic Medal Performance: What Have We Learned 25 Years After Implementation?

BACKGROUND

Altitude training is often regarded as an indispensable tool for the success of elite endurance athletes. Historically, altitude training emerged as a key strategy to prepare for the 1968 Olympics, held at 2300 m in Mexico City, and was limited to the "Live High-Train High" method for endurance athletes aiming for performance gains through improved oxygen transport. This "classical" intervention was modified in 1997 by the "Live High-Train Low" (LHTL) model wherein athletes supplemented acclimatization to chronic hypoxia with high-intensity training at low altitude.

PURPOSE

This review discusses important considerations for successful implementation of LHTL camps in elite athletes based on experiences, both published and unpublished, of the authors.

APPROACH

The originality of our approach is to discuss 10 key "lessons learned," since the seminal work by Levine and Stray-Gundersen was published in 1997, and focusing on (1) optimal dose, (2) individual responses, (3) iron status, (4) training-load monitoring, (5) wellness and well-being monitoring, (6) timing of the intervention, (7) use of natural versus simulated hypoxia, (8) robustness of adaptative mechanisms versus performance benefits, (9) application for a broad range of athletes, and (10) combination of methods. Successful LHTL strategies implemented by Team USA athletes for podium performance at Olympic Games and/or World Championships are presented.

CONCLUSIONS

The evolution of the LHTL model represents an essential framework for sport science, in which field-driven questions about performance led to critical scientific investigation and subsequent practical implementation of a unique approach to altitude training.

Acute and Chronic Performance Enhancement in Rowing: A Network Meta-analytical Approach on the Effects of Nutrition and Training

INTRODUCTION

This systematic review and network meta-analysis assessed via direct and indirect comparison the occurrence and magnitude of effects following different nutritional supplementation strategies and exercise interventions on acute and chronic rowing performance and its surrogates.

METHODS

PubMed, Web of Science, PsycNET and SPORTDiscus searches were conducted until March 2022 to identify studies  that met the following inclusion criteria: (a) controlled trials, (b) rowing performance and its surrogate parameters as outcomes, and (c) peer-reviewed and published in English. Frequentist network meta-analytical approaches were calculated based on standardized mean differences (SMD) using random effects models.

RESULTS

71 studies with 1229 healthy rowers (aged 21.5 ± 3.0 years) were included and two main networks (acute and chronic) with each two subnetworks for nutrition and exercise have been created. Both networks revealed low heterogeneity and non-significant inconsistency (I² ≤ 35.0% and Q statistics: p ≥ 0.12). Based on P-score rankings, while caffeine (P-score 84%; SMD 0.43) revealed relevantly favorable effects in terms of acute rowing performance enhancement, whilst prior weight reduction (P-score 10%; SMD - 0.48) and extensive preload (P-score 18%; SMD - 0.34) impaired acute rowing performance. Chronic blood flow restriction training (P-score 96%; SMD 1.26) and the combination of β-hydroxy-β-methylbutyrate and creatine (P-score 91%; SMD 1.04) induced remarkably large positive effects, while chronic spirulina (P-score 7%; SMD - 1.05) and black currant (P-score 9%; SMD - 0.88) supplementation revealed impairment effects.

CONCLUSION

Homogeneous and consistent findings from numerous studies indicate that the choice of nutritional supplementation strategy and exercise training regimen are vital for acute and chronic performance enhancement in rowing.

A study of survival strategies for improving acclimatization of lowlanders at high-altitude

Human Acclimatization and therapeutic approaches are the core components for conquering the physiological variations at high altitude (≥2500 m) exposure. The declined atmospheric pressure and reduced partial pressure of oxygen at high altitudes tend to decrease the temperature by several folds. Hypobaric hypoxia is a major threat to humanity at high altitudes, and its potential effects include altitude mountain sickness. On severity, it may lead to the development of conditions like high-altitude cerebral edema (HACE) or high-altitude pulmonary edema (HAPE) and cause unexpected physiological changes in the healthy population of travelers, athletes, soldiers, and low landers while sojourning at high altitude. Previous investigations have been done on long-drawn-out acclimatization strategies such as the staging method to prevent the damage caused by high-altitude hypobaric Hypoxia. Inherent Limitations of this strategy hamper the daily lifestyle and time consuming for people. It is not suitable for the rapid mobilization of people at high altitudes. There is a need to recalibrate acclimatization strategies for improving health protection and adapting to the environmental variations at high altitudes. This narrative review details the geographical changes and physiological changes at high altitudes and presents a framework of acclimatization, pre-acclimatization, and pharmacological aspects of high-altitude survival to enhance the government efficacy and capacity for the strategic planning of acclimatization, use of therapeutics, and safe de-induction from high altitude for minimizing the life loss. It's simply too ambitious for the importance of the present review to reduce life loss, and it can be proved as the most essential aspect of the preparatory phase of high-altitude acclimatization in plateau regions without hampering the daily lifestyle. The application of pre-acclimatization techniques can be a boon for people serving at high altitudes, and it can be a short bridge for the rapid translocation of people at high altitudes by minimizing the acclimatization time.

Living high - training low model applied to C57BL/6J mice: Effects on physiological parameters related to aerobic fitness and acid-base balance

There is a scarcity of data regarding the acclimation to high altitude (hypoxic environment) accompanied by training at low altitude (normoxic conditions), the so-called "living high-training low" (LHTL) model in rodents. We aimed to investigate the effects of aerobic training on C57BL/6J mice living in normoxic (NOR) or hypoxic (HYP) environments on several parameters, including critical velocity (CV), a parameter regarded as a measure of aerobic capacity, on monocarboxylate transporters (MCTs) in muscles and hypothalamus, as well as on hematological parameters and body temperature. In each environment, mice were divided into non-trained (N) and trained (T). Forty rodents were distributed into the following experimental groups (N-NOR; T-NOR; N-HYP and T-HYP). HYP groups were in a normobaric tent where oxygen-depleted air was pumped from a hypoxia generator set an inspired oxygen fraction [FiO₂] of 14.5 %. The HYP-groups were kept (18 h per day) in a normobaric tent for consecutive 8-weeks. Training sessions were conducted in normoxic conditions ([FiO₂] = 19.5 %), 5 times per week (40 min per session) at intensity equivalent to 80 % of CV. In summary, eight weeks of LHTL did not promote a greater improvement in the CV, protein expression of MCTs in different tissues when compared to the application of training alone. The LHTL model increased red blood cells count, but reduced hemoglobin per erythrocyte was found in mice exposed to LHTL. Although the LHTL did not have a major effect on thermographic records, exercise-induced hyperthermia (in the head) was attenuated in HYP groups when compared to NOR groups.

Monitoring Physiological Performance over 4 Weeks Moderate Altitude Training in Elite Chinese Cross-Country Skiers: An Observational Study

The current observational study aimed to monitor the physiological performance over 4 weeks of living and training at a moderate altitude in elite Chinese cross-country skiers (8 males, mean age 20.83 ± 1.08 years). Lactate threshold, maximal oxygen uptake, blood, and body composition tests were performed at different time points to investigate the changes in physiological performance. The data were analysed by a one-way repeated measures ANOVA and a paired sample T-test between the test results. During the training camp, systematic load monitoring was carried out. Lactate threshold velocity, lactate threshold heart rate, and upper body muscle mass increased significantly (p < 0.01) after moderate altitude training. Maximum oxygen uptake was reduced compared to pre-tests (p < 0.05). Aerobic capacity parameters (maximal oxygen uptake, haemoglobin, red blood cell count) did not significantly increase after athletes returned to sea level (p > 0.05). These findings suggest that 4 weeks of moderate altitude training can significantly improve athletes’ lactate threshold and upper body muscle mass; no significant improvement in other aerobic capacity was seen. Exposure time, training load, and nutritional strategies should be thoroughly planned for optimal training of skiers at moderate altitudes.

Primum non nocere; It's time to consider altitude training as the medical intervention it actually is!

Sleep is one of the most important aspects of recovery, and is known to be severely affected by hypoxia. The present position paper focuses on sleep as a strong moderator of the altitude training-response. Indeed, the response to altitude training is highly variable, it is not a fixed and classifiable trait, rather it is a state that is determined by multiple factors (e.g., iron status, altitude dose, pre-intervention hemoglobin mass, training load, and recovery). We present an overview of evidence showing that sleep, and more specifically the prolonged negative impact of altitude on the nocturnal breathing pattern, affecting mainly deep sleep and thus the core of physiological recovery during sleep, could play an important role in intra- and interindividual variability in the altitude training-associated responses in professional and recreational athletes. We conclude our paper with a set of suggested recommendations to customize the application of altitude training to the specific needs and vulnerabilities of each athlete (i.e., primum non nocere). Several factors have been identified (e.g., sex, polymorphisms in the TASK2/KCNK5, NOTCH4 and CAT genes and pre-term birth) to predict individual vulnerabilities to hypoxia-related sleep-disordered breathing. Currently, polysomnography should be the first choice to evaluate an individual's predisposition to a decrease in deep sleep related to hypoxia. Further interventions, both pharmacological and non-pharmacological, might alleviate the effects of nocturnal hypoxia in those athletes that show most vulnerable.

Training at moderate altitude improves submaximal but not maximal performance-related parameters in elite rowers

Maximal oxygen consumption (V̇O_2max), physiological thresholds, and hemoglobin mass are strong predictors of endurance performance. High values of V̇O_2max, maximal aerobic power (MAP), and power output at anaerobic thresholds are key variables in elite rowers. Endurance athletes often use altitude training as a strategy to improve performance. However, no clear evidence exists that training at natural altitude enhances sea-level performance in elite rowers. This study aimed to evaluate the effect of altitude training on rowing-performance parameters at sea level. The study was conducted on eleven rowers (Six females, five males) from the Chilean National Team during a 3-week moderate altitude training (∼2,900 m. a.s.l.) under the live high-train high (LHTH) model. It included a rowing ergometer maximal incremental test and blood analysis (pre and post-altitude). Gas exchange analysis was performed to measure V̇O_2max, ventilatory thresholds (VTs) and rowing economy/efficiency (ECR/GE%). LHTL training improves performance-related variables at sea level (V̇E_max: 3.3% (95% CI, 1.2–5.5); hemoglobin concentration ([Hb]): 4.3% (95% CI, 1.7–6.9); hematocrit (%): 4.5% (95% CI, 0.9–8.2); RBC (red blood cells) count: 5.3% (95% CI, 2.3–8.2); power at VT2: 6.9% (95% CI, 1.7–12.1), V̇E_VT2: 6.4% (95% CI, 0.4–12.4); power at VT1: 7.3% (95% CI, 1.3–13.3), V̇E_VT1: 8.7% (95% CI, 1.6–15.8)) and economy/efficiency-related variables (ECR_VT2: 5.3% (95% CI, −0.6 to −10.0); GE(%): 5.8% (95% CI, 0.8–10.7)). The LHTH training decreased breathing economy at MAP (−2.8% (95% CI, 0.1–5.6)), pVT2 (−9.3% (95% CI, −5.9 to −12.7)), and pVT1 (−9.3% (95% CI, −4.1 to −14.4)). Non-significant changes were found for V̇O_2max and MAP. This study describes the effects of a 3-week moderate altitude (LHTH training) on performance and economy/efficiency-related variables in elite rowers, suggesting that it is an excellent option to induce positive adaptations related to endurance performance.

Genetics of long-distance runners and road cyclists-A systematic review with meta-analysis

The aim of this systematic review and meta-analysis was to identify the genetic variants of (inter)national competing long-distance runners and road cyclists compared with controls. The Medline and Embase databases were searched until 15 November 2021. Eligible articles included genetic epidemiological studies published in English. A homogenous group of endurance athletes competing at (inter)national level and sedentary controls were included. Pooled odds ratios based on the genotype frequency with corresponding 95% confidence intervals (95%CI) were calculated using random effects models. Heterogeneity was addressed by Q-statistics, and I² . Sources of heterogeneity were examined by meta-regression and risk of bias was assessed with the Clark Baudouin scale. This systematic review comprised of 43 studies including a total of 3938 athletes and 10 752 controls in the pooled analysis. Of the 42 identified genetic variants, 13 were investigated in independent studies. Significant associations were found for five polymorphisms. Pooled odds ratio [95%CI] favoring athletes compared with controls was 1.42 [1.12-1.81] for ACE II (I/D), 1.66 [1.26-2.19] for ACTN3 TT (rs1815739), 1.75 [1.34-2.29] for PPARGC1A GG (rs8192678), 2.23 [1.42-3.51] for AMPD1 CC (rs17602729), and 2.85 [1.27-6.39] for HFE GG + CG (rs1799945). Risk of bias was low in 25 (58%) and unclear in 18 (42%) articles. Heterogeneity of the results was low (0%-20%) except for HFE (71%), GNB3 (80%), and NOS3 (76%). (Inter)national competing runners and cyclists have a higher probability to carry specific genetic variants compared with controls. This study confirms that (inter)national competing endurance athletes constitute a unique genetic make-up, which likely contributes to their performance level.

Remote ischemic preconditioning enhances aerobic performance by accelerating regional oxygenation and improving cardiac function during acute hypobaric hypoxia exposure

Remote ischemic preconditioning (RIPC) may improve exercise performance. However, the influence of RIPC on aerobic performance and underlying physiological mechanisms during hypobaric hypoxia (HH) exposure remains relatively uncertain. Here, we systematically evaluated the potential performance benefits and underlying mechanisms of RIPC during HH exposure. Seventy-nine healthy participants were randomly assigned to receive sham intervention or RIPC (4 × 5 min occlusion 180 mm Hg/reperfusion 0 mm Hg, bilaterally on the upper arms) for 8 consecutive days in phases 1 (24 participants) and phase 2 (55 participants). In the phases 1, we measured the change in maximal oxygen uptake capacity (VO₂max) and muscle oxygenation (SmO₂) on the leg during a graded exercise test. We also measured regional cerebral oxygenation (rSO₂) on the forehead. These measures and physiological variables, such as cardiovascular hemodynamic parameters and heart rate variability index, were used to evaluate the intervention effect of RIPC on the changes in bodily functions caused by HH exposure. In the phase 2, plasma protein mass spectrometry was then performed after RIPC intervention, and the results were further evaluated using ELISA tests to assess possible mechanisms. The results suggested that RIPC intervention improved VO₂max (11.29%) and accelerated both the maximum (18.13%) and minimum (53%) values of SmO₂ and rSO₂ (6.88%) compared to sham intervention in hypobaric hypoxia exposure. Cardiovascular hemodynamic parameters (SV, SVRI, PPV% and SpMet%) and the heart rate variability index (Mean RR, Mean HR, RMSSD, pNN50, Lfnu, Hfnu, SD1, SD2/SD1, ApEn, SampEn, DFA1and DFA2) were evaluated. Protein sequence analysis showed 42 unregulated and six downregulated proteins in the plasma of the RIPC group compared to the sham group after HH exposure. Three proteins, thymosin β4 (Tβ4), heat shock protein-70 (HSP70), and heat shock protein-90 (HSP90), were significantly altered in the plasma of the RIPC group before and after HH exposure. Our data demonstrated that in acute HH exposure, RIPC mitigates the decline in VO₂max and regional oxygenation, as well as physiological variables, such as cardiovascular hemodynamic parameters and the heart rate variability index, by influencing plasma Tβ4, HSP70, and HSP90. These data suggest that RIPC may be beneficial for acute HH exposure.

Multiple N-of-1 trials to investigate hypoxia therapy in Parkinson's disease: study rationale and protocol

Background

Parkinson’s disease (PD) is a neurodegenerative disease, for which no disease-modifying therapies exist. Preclinical and clinical evidence suggest that hypoxia-based therapy might have short- and long-term benefits in PD. We present the contours of the first study to assess the safety, feasibility and physiological and symptomatic impact of hypoxia-based therapy in individuals with PD.

Methods/Design

In 20 individuals with PD, we will investigate the safety, tolerability and short-term symptomatic efficacy of continuous and intermittent hypoxia using individual, double-blind, randomized placebo-controlled N-of-1 trials. This design allows for dose finding and for including more individualized outcomes, as each individual serves as its own control. A wide range of exploratory outcomes is deployed, including the Movement Disorders Society Unified Parkinson’s Disease Rating scale (MDS-UPDRS) part III, Timed Up & Go Test, Mini Balance Evaluation Systems (MiniBES) test and wrist accelerometry. Also, self-reported impression of overall symptoms, motor and non-motor symptoms and urge to take dopaminergic medication will be assessed on a 10-point Likert scale. As part of a hypothesis-generating part of the study, we also deploy several exploratory outcomes to probe possible underlying mechanisms of action, including cortisol, erythropoietin and platelet-derived growth factor β. Efficacy will be assessed primarily by a Bayesian analysis.

Discussion

This evaluation of hypoxia therapy could provide insight in novel pathways that may be pursued for PD treatment. This trial also serves as a proof of concept for deploying an N-of-1 design and for including individualized outcomes in PD research, as a basis for personalized treatment approaches.

Trial registration

ClinicalTrials.gov Identifier: NCT05214287 (registered January 28, 2022).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02770-7.

Effects of the ketogenic diet on performance and body composition in athletes and trained adults: a systematic review and Bayesian multivariate multilevel meta-analysis and meta-regression

This systematic review with meta-analysis aimed to determine the effects of the ketogenic diet (KD) against carbohydrate (CHO)-rich diets on physical performance and body composition in trained individuals. The MEDLINE, EMBASE, CINAHL, SPORTDiscus, and The Cochrane Library were searched. Randomized and non-randomized controlled trials in athletes/trained adults were included. Meta-analytic models were carried out using Bayesian multilevel models. Eighteen studies were included providing estimates on cyclic exercise modes and strength one-maximum repetition (1-RM) performances and for total, fat, and free-fat masses. There were more favorable effects for CHO-rich than KD on time-trial performance (mode [95% credible interval]; -3.3% [-8.5%, 1.7%]), 1-RM (-5.7% [-14.9%, 2.6%]), and free-fat mass (-0.8 [-3.4, 1.9] kg); effects were more favorable to KD on total (-2.4 [-6.2, 1.8] kg) and fat mass losses (-2.4 [-5.4, 0.2] kg). Likely modifying effects on cyclic performance were the subject's sex and VO2max, intervention and performance durations, and mode of exercise. The intervention duration and subjects' sex were likely to modify effects on total body mass. KD can be a useful strategy for total and fat body losses, but a small negative effect on free-fat mass was observed. KD was not suitable for enhancing strength 1-RM or high-intensity cyclic performances.

The effects of a respiratory training mask on steady-state oxygen consumption at rest and during exercise

No studies have directly measured ventilatory and metabolic responses while wearing a respiratory training mask (RTM) at rest and during exercise. Eleven aerobically fit adults (age: 21 ± 1 years) completed a randomized cross-over study while wearing an RTM or control mask during cycling at 50% Wmax. An RTM was retrofitted with a gas collection tube and set to the manufacturer's "altitude resistance" setting of 6,000 ft (1,800 m). Metabolic gas analysis, ratings of perceived exertion, and oxygen saturation (SpO2) were measured during rest and cycling exercise. The RTM did not affect metabolic, ventilation, and SpO2 at rest compared to the control mask (all, effect of condition: P > 0.05). During exercise, the RTM blunted respiratory rate and minute ventilation (effect of condition: P < 0.05) compared to control. Similar increases in VO2 and VCO2 were observed in both conditions (both, effect of condition: P > 0.05). However, the RTM led to decreased fractional expired O2 and increased fractional expired CO2 (effect of condition: P < 0.05) compared to the control mask. In addition, the RTM decreased SpO2 and increased RPE (both, effect of condition: P < 0.05) during exercise. Despite limited influence on ventilation and metabolism at rest, the RTM reduces ventilation and disrupts gas concentrations during exercise leading to modest hypoxemia.

The Effect of Normobaric Hypoxia in Middle- and/or Long-Distance Runners: Systematic Review

BACKGROUND

The use of normobaric hypoxia can bring benefits to sports performance because it improves haematological parameters and/or physical activity tests. Our objective was to conduct a systematic review so as to analyse the methods used in hypoxia and to detect its effects on middle- and/or long-distance runners.

METHODS

Research was conducted using five electronic databases (PubMed, SportDiscus, Cochrane Library, Scopus and PEDro) until December 2021. The methodological quality of the included studies was assessed using the PEDro scale.

RESULTS

Having analysed 158 studies, 12 were chosen for the qualitative and quantitative synthesis. A significant improvement on time until exhaustion was detected, and oxygen saturation decreased after the intervention. There were no significant changes in the 3000-metre time trial or in the haematocrit percentage. The changes in percentage of reticulocytes, heart rate, maximal heart rate, lactate concentration and erythropoietin were heterogeneous between the different research studies.

CONCLUSION

short exposure (less than 3 h to normobaric hypoxia significantly increases the time to exhaustion). However, longer exposure times are necessary to increase haemoglobin. Altitude and exposure time are highly heterogeneous in the included studies.

Neuromuscular Adaptations in Elite Swimmers During Concurrent Strength and Endurance Training at Low and Moderate Altitudes

ABSTRACT

Tomazin, K, Strojnik, V, Feriche, B, Garcia Ramos, A, Štrumbelj, B, and Stirn, I. Neuromuscular adaptations in elite swimmers during concurrent strength and endurance training at low and moderate altitudes. J Strength Cond Res 36(4): 1111-1119, 2022-This study evaluated neuromuscular adaptations in elite swimmers during concurrent strength and endurance training (SET) at low (295 m) and moderate (2,320 m) altitudes. Sixteen elite swimmers took part in a 3-week SET during a general preparation phase. All neuromuscular tests were performed a week before and after a SET. In posttraining, maximal knee isometric torque (TMVC) and soleus H-reflex remained statistically unchanged for sea-level (SL) and for altitude (AL) training. Rate of torque development (RTD) decreased post-SL (-14.5%; p < 0.01) but not post-AL (-4.7%; p > 0.05) training. Vastus lateralis electromyographic (EMG) activity during RTD decreased post-SL (-17.0%; P = 0.05) but not post-AL (4.8%; p > 0.05) training. Quadriceps twitch torque (TTW) significantly increased post-AL (12.1%; p < 0.01) but not post-SL (-1.0%; p > 0.05; training × altitude: F1,15 = 12.4; p < 0.01) training. Quadriceps twitch contraction time and M-wave amplitude remained statistically unchanged post-SL and post-AL training. After SL training, increment in TMVC was accompanied with increment in vastus lateralis EMG (R = 0.76; p < 0.01) and TTW (R = 0.48; p < 0.06). Posttraining in AL, increment in TMVC was accompanied with increment in TTW (R = 0.54; p < 0.05). Strength and endurance training at altitude seems to prompt adaptations in twitch contractile properties. In contrast, SET performed at SL may hamper the magnitude of neural adaptations to strength training, particularly during rapid voluntary contractions. In conclusion, SET at AL might benefit muscular adaptations in swimmers compared with training at SL.

High Intraindividual Variability in the Response of Serum Erythropoietin to Multiple Simulated Altitude Exposures

Baranauskas, Marissa N., Timothy J. Fulton, Alyce D. Fly, Bruce J. Martin, Timothy D. Mickleborough, and Robert F. Chapman. High intraindividual variability in the response of serum erythropoietin to multiple simulated altitude exposures. High Alt Med Biol. 23:85-89, 2022. Purpose: To evaluate within-subject variability in the serum erythropoietin (EPO) response to multiple simulated altitude exposures. Methods: Seven physically active men and women (age 27 ± 3 years, body mass index = 24.6 ± 4.0 kg/m²) were exposed to normobaric hypoxia (fraction of inspired oxygen [F_iO₂] = 0.14) for 12 hours on three separate occasions. Serum EPO concentrations were measured before exposure (0 hour), after 6 hours, and after 12 hours in hypoxia. The EPO response to hypoxia was calculated as percent change from 0 to 12 hours (ΔEPO_0-12). Results: Exposure time had a significant effect on EPO (p < 0.001) with concentrations increasing 3.2 ± 1.3 mIU/ml from 0 to 6 hours (p = 0.034) and 4.7 ± 1.2 mIU/ml from 0 to 12 hours (p = 0.001). Group mean ΔEPO_0-12 remained unchanged (p = 0.688) between the three exposures; however, there was considerable intraindividual variability in EPO responses. The intrasubject coefficient of variation for ΔEPO_0-12 was 61% ± 28% (range: 17%-103%) with intrasubject associations ranging r = 0.052 to r = 0.651 between repeated exposures. Conclusions: Athletes who routinely supplement training with simulated altitude methods (e.g., hypoxic tents) should expect inconsistent EPO responses to intermittent exposures lasting ≤12 hours.

Complex networks analysis reinforces centrality hematological role on aerobic-anaerobic performances of the Brazilian Paralympic endurance team after altitude training

This study investigated the 30-days altitude training (2500 m, LHTH-live and training high) on hematological responses and aerobic–anaerobic performances parameters of high-level Paralympic athletes. Aerobic capacity was assessed by 3000 m run, and anaerobic variables (velocity, force and mechanical power) by a maximal 30-s semi-tethered running test (AO30). These assessments were carried out at low altitude before (PRE) and after LHTH (5–6 and 15–16 days, POST1 and POST2, respectively). During LHTH, hematological analyzes were performed on days 1, 12, 20 and 30. After LHTH, aerobic performance decreased 1.7% in POST1, but showed an amazing increase in POST2 (15.4 s reduction in the 3000 m test, 2.8%). Regarding anaerobic parameters, athletes showed a reduction in velocity, force and power in POST1, but velocity and power returned to their initial conditions in POST2. In addition, all participants had higher hemoglobin (Hb) values at the end of LHTH (30 days), but at POST2 these results were close to those of PRE. The centrality metrics obtained by complex networks (pondered degree, pagerank and betweenness) in the PRE and POST2 scenarios highlighted hemoglobin, hematocrit (Hct) and minimum force, velocity and power, suggesting these variables on the way to increasing endurance performance. The Jaccard’s distance metrics showed dissimilarity between the PRE and POST2 graphs, and Hb and Hct as more prominent nodes for all centrality metrics. These results indicate that adaptive process from LHTH was highlighted by the complex networks, which can help understanding the better aerobic performance at low altitude after 16 days in Paralympic athletes.

Physiological Considerations to Support Podium Performance in Para-Athletes

The twenty-first century has seen an increase in para-sport participation and the number of research publications on para-sport and the para-athlete. Unfortunately, the majority of publications are case reports/case series or study single impairment types in isolation. Indeed, an overview of how each International Paralympic Committee classifiable impairment type impact athlete physiology, health, and performance has not been forthcoming in the literature. This can make it challenging for practitioners to appropriately support para-athletes and implement evidence-based research in their daily practice. Moreover, the lack of a cohesive publication that reviews all classifiable impairment types through a physiological lens can make it challenging for researchers new to the field to gain an understanding of unique physiological challenges facing para-athletes and to appreciate the nuances of how various impairment types differentially impact para-athlete physiology. As such, the purpose of this review is to (1) summarize how International Paralympic Committee classifiable impairments alter the normal physiological responses to exercise; (2) provide an overview of "quick win" physiological interventions targeted toward specific para-athlete populations; (3) discuss unique practical considerations for the para-sport practitioner; (4) discuss research gaps and highlight areas for future research and innovation, and (5) provide suggestions for knowledge translation and knowledge sharing strategies to advance the field of para-sport research and its application by para-sport practitioners.

The Modifications of Haemoglobin, Erythropoietin Values and Running Performance While Training at Mountain vs. Hilltop vs. Seaside

Altitude training increases haemoglobin, erythropoietin values among athletes, but may have negative physiological consequences. An alternative, although less explored, that has the potential to positively influence performance while avoiding some of the negative physiological consequences of hypoxia is sand training. Ten endurance-trained athletes (age: 20.8 ± 1.4, body mass: 57.7 ± 8.2 kg, stature: 176 ± 6 cm; 5000 m 14:55.00 ± 0:30 min) performed three 21-day training camps at different locations: at a high altitude (HIGH), at the sea-level (CTRL), at the sea-level on the sand (SAND). Differences in erythropoietin (EPO) and haemoglobin (Hb) concentration, body weight, VO_2max and maximal aerobic velocity (VMA) before and after each training cycle were compared. Data analysis has indicated that training during HIGH elicited a greater increase in VO_2max (2.4 ± 0.2%; p = 0.005 and 1.0 ± 0.2%; p < 0.001) and VMA (2.4 ± 0.2%, p < 0.001 and 1.2 ± 0.2%; p = 0.001) compared with CTRL and SAND. While increases in VO_2max and VMA following SAND were greater (1.3 ± 0.1%; p < 0.001 and 1.2 ± 0.1%; p < 0.001) than those observed after CTRL. Moreover, EPO increased to a greater extent following HIGH (25.3 ± 2.7%) compared with SAND (11.7 ± 1.6%, p = 0.008) and CTRL (0.1 ± 0.3%, p < 0.001) with a greater increase (p < 0.01) following SAND compared with CTRL. Furthermore, HIGH and SAND elicited a greater increase (4.9 ± 0.9%; p = 0.001 and 3.3 ± 1.1%; p = 0.035) in Hb compared with CTRL. There was no difference in Hb changes observed between HIGH and SAND (p = 1.0). Finally, athletes lost 2.1 ± 0.4% (p = 0.001) more weight following HIGH vs. CTRL, while there were no differences in weight changes between HIGH vs. SAND (p = 0.742) and SAND vs. CTRL (p = 0.719). High-altitude training and sea-level training on sand resulted in significant improvements in EPO, Hb, VMA, and VO_2max that exceeded changes in such parameters following traditional sea-level training. While high-altitude training elicited greater relative increases in EPO, VMA, and VO_2max, sand training resulted in comparable increases in Hb and may prevent hypoxia-induced weight loss.

Pitfalls in interpreting red blood cell parameters in elite high-altitude and sea-level athletes: A unique case series

Standard routine hematological measurements are commonly used to investigate differences in blood parameters between high-altitude athletes (HAA) and sea-level athletes (SLA), and to monitor the effect of high-altitude training. In this way, red blood cell (RBC) parameters are usually expressed as relative parameters (concentration) rather than absolute parameters (total amount). In this unique case series of elite HAA and SLA, we describe how different ways of parameter expression can affect the interpretation of blood tests. In a group of 42 elite athletes, relative and absolute RBC parameters were compared between HAA and SLA. Absolute parameters were calculated by multiplying relative values with formula-based estimated blood volume (BV-e). Additionally, in two individual athletes, one HAA and one SLA, absolute parameters were also calculated with blood volume (BV) obtained by measurement with a dilution method (BV-m). In men, HAA had a significantly higher hemoglobin (Hb) concentration (+7.8%; p = 0.001) and total Hb mass per kg body weight (BW) (+12.0%; p = 0.002). When not corrected for BW, HAA had a lower, non-significant, total Hb mass (-7.8%; p = 0.055). In women, no significant differences between HLA and SLA were observed. The two individual athletes showed that, based on BV-m, in the HAA, total Hb mass and total Hb mass per kg BW were respectively 14.1% and 31.0% higher than in the SLA, whereas based on BV-e, in the HAA, total Hb mass was 20.8% lower and total Hb mass per kg BW was only 2.4% higher. Similar inconsistencies were observed for total RBC count. Thus, different ways of parameter expression, and different methods of BV assessment for the calculation of absolute parameter values, influence the interpretation of blood tests in athletes, which may lead to misinterpretation and incorrect conclusions.

Aerobic Continuous and Interval Training under Hypoxia Enhances Endurance Exercise Performance with Hemodynamic and Autonomic Nervous System Function in Amateur Male Swimmers

Hypoxic training is often performed by competitive swimmers to enhance their performance in normoxia. However, the beneficial effects of aerobic continuous and interval training under hypoxia on hemodynamic function, autonomic nervous system (ANS) function, and endurance exercise performance remain controversial. Here we investigated whether six weeks of aerobic continuous and interval training under hypoxia can improve hematological parameters, hemodynamic function, ANS function, and endurance exercise performance versus normoxia in amateur male swimmers. Twenty amateur male swimmers were equally assigned to the hypoxic training group or normoxic training group and evaluated before and after six weeks of training. Aerobic continuous and interval training in the hypoxia showed a more significantly improved hemodynamic function (heart rate, −653.4 vs. −353.7 beats/30 min; oxygen uptake, −62.45 vs. −16.22 mL/kg/30 min; stroke volume index, 197.66 vs. 52.32 mL/30 min) during submaximal exercise, ANS function (root mean square of successive differences, 10.15 vs. 3.32 ms; total power, 0.72 vs. 0.20 ms²; low-frequency/high-frequency ratio, −0.173 vs. 0.054), and endurance exercise performance (maximal oxygen uptake, 5.57 vs. 2.26 mL/kg/min; 400-m time trial record, −20.41 vs. −7.91 s) than in the normoxia. These indicate that hypoxic training composed of aerobic continuous and interval exercise improves the endurance exercise performance of amateur male swimmers with better hemodynamic function and ANS function.

Heat acclimation training with intermittent and self-regulated intensity may be used as an alternative to traditional steady state and power-regulated intensity in endurance cyclists

The study aimed to determine the effects of self-regulated and variable intensities sustained during short-term heat acclimation training on cycling performance. Seventeen competitive-level male athletes performed a 20-km cycling time trial before (TT-PRE), immediately after (TT-POST1) and one week after (TT-POST2) a 5-day acclimation training program, including either RPE-regulated intermittent (HA-HIT, N = 9) or fixed and low-intensity (HA-LOW, N = 8) training sessions in the heat (39 °C; 40% relative humidity). Total training volume was 23% lower in HA-HIT compared to HA-LOW. Physiological responses were evaluated during a 40-min fixed-RPE cycling exercise performed before (HST-PRE) and immediately after (HST-POST) heat acclimation. All participants in HA-LOW group tended to improve mean power output from TT-PRE to TT-POST1 (+8.1 ± 5.2%; ES = 0.55 ± 0.23), as well as eight of the nine athletes in HA-HIT group (+4.3 ± 2.0%; ES = 0.29 ± 0.31) without difference between groups, but TT-POST2 results showed that improvements were dissipated one week after. Similar improvements in thermal sensation and lower elevations of core temperature in HST-POST following HA-LOW and HA-HIT training protocols suggest that high intensity and RPE regulated bouts could be an efficient strategy for short term heat acclimation protocols, for example prior to the competition. Furthermore, the modest impact of lowered thermal sensation on cycling performance confirms that perceptual responses of acclimated athletes are dissociated from physiological stress when exercising in the heat.

[Into thin air - Altitude training and hypoxic conditioning: From athlete to patient]

INTRODUCTION

Hypoxic exposure should be considered as a continuum, the effects of which depend on the dose and individual response to hypoxia. Hypoxic conditioning (HC) represents an innovative and promising strategy, ranging from improved human performance to therapeutic applications.

STATE OF THE ART

With the aim of improving sports performance, the effectiveness of hypoxic exposure, whether natural or simulated, is difficult to demonstrate because of the large variability of the protocols used. In therapeutics, the benefits of HC are described in many pathological conditions such as obesity or cardiovascular pathologies. If the HC benefits from a strong preclinical rationale, its application to humans remains limited.

PERSPECTIVES

Advances in training and acclimation will require greater personalization and precise periodization of hypoxic exposures. For patients, the harmonization of HC protocols, the identification of biomarkers and the development and subsequent validation of devices allowing a precise control of the hypoxic stimulus are necessary steps for the development of HC.

CONCLUSIONS

From the athlete to the patient, HC represents an innovative and promising field of research, ranging from the improvement of human performance to the prevention and treatment of certain pathologies.

Four weeks of high-intensity training in moderate, but not mild hypoxia improves performance and running economy more than normoxic training in horses

We investigated whether horses trained in moderate and mild hypoxia demonstrate greater improvement in performance and aerobic capacity compared to horses trained in normoxia and whether the acquired training effects are maintained after 2 weeks of post‐hypoxic training in normoxia. Seven untrained Thoroughbred horses completed 4 weeks (3 sessions/week) of three training protocols, consisting of 2‐min cantering at 95% maximal oxygen consumption V˙O2max under two hypoxic conditions (H16, F_IO₂ = 16%; H18, F_IO₂ = 18%) and in normoxia (N21, F_IO₂ = 21%), followed by 2 weeks of post‐hypoxic training in normoxia, using a randomized crossover study design with a 3‐month washout period. Incremental treadmill tests (IET) were conducted at week 0, 4, and 6. The effects of time and groups were analyzed using mixed models. Run time at IET increased in H16 and H18 compared to N21, while speed at V˙O2max was increased significantly only in H16. V˙O2max in all groups and cardiac output at exhaustion in H16 and H18 increased after 4 weeks of training, but were not significantly different between the three groups. In all groups, run time, V˙O2max, VV˙O2max, Q˙max, and lactate threshold did not decrease after 2 weeks of post‐hypoxic training in normoxia. These results suggest that 4 weeks of training in moderate (H16), but not mild (H18) hypoxia elicits greater improvements in performance and running economy than normoxic training and that these effects are maintained for 2 weeks of post‐hypoxic training in normoxia.

Cardiorespiratory Response and Power Output During Submaximal Exercise in Normobaric Versus Hypobaric Hypoxia: A Pilot Study Using a Specific Chamber that Controls Environmental Factors

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. 22: 201-208, 2021. Background: 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. Methods: 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 (P_ETCO₂) were monitored throughout the experiment. Results: SpO₂, P_ETCO₂, 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 P_ETCO₂ than did high-intensity exercise in NH (NH vs. HH; 54.2 ± 5.9 mmHg vs. 57.2 ± 3.4 mmHg, p < 0.01). Conclusions: 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.

Heat Versus Altitude Training for Endurance Performance at Sea Level

Environmental stressors, such as heat or altitude, elicit dissimilar physiological adaptations to endurance training programs. Whether these differences (i.e., increased hemoglobin mass vs plasma volume) differentially influence performance is debated. We review data in support of our novel hypothesis, which proposes altitude as the preferred environmental training stimulus for elite endurance athletes preparing to compete in temperate, sea-level climates (5°C-18°C).

Effect of a 16-Day Altitude Training Camp on 3,000-m Steeplechase Running Energetics and Biomechanics: A Case Study

The purpose of this study was to investigate the effect of a 16-day training camp at moderate altitude on running energetics and biomechanics in an elite female 3,000-m steeplechase athlete (personal best: 9 min 36.15 s). The 16-day intervention included living and training at 1,600 m altitude. A maximal incremental test was performed at sea level to determine the maximal oxygen uptake (V∙O2max). Before (pre-) and after (post-) intervention, the participant performed a specific training session consisting of 10 × 400 m with 5 hurdles with oxygen uptake (V∙O2), blood lactate, stride length and stride rate being measured. A video analysis determined take-off distance and landing around the hurdle (DT_H and DL_H), take-off velocity and landing around the hurdle (VT_H and VL_H), and the maximal height over the hurdle (M_H). The results demonstrated that the mean V∙O2 maintained during the ten 400 m trials represented 84–86% of V∙O2max and did not change from pre- to post-intervention (p = 0.22). Mean blood lactate measured on the 6 last 400-m efforts increased significantly (12.0 ± 2.2 vs. 17.0 ± 1.6 mmol.l⁻¹; p < 0.05). On the other hand, post-intervention maximal lactate decreased from 20.1 to 16.0 mmol.l⁻¹. Biomechanical analysis revealed that running velocity increased from 5.12 ± 0.16 to 5.49 ± 0.19 m.s⁻¹ (p < 0.001), concomitantly with stride length (1.63 ± 0.05 vs. 1.73 ± 0.06 m; p < 0.001). However, stride rate did not change (3.15 ± 0.03 vs. 3.16 ± 0.02 Hz; p = 0.14). While DT_H was not significantly different from pre- to post- (1.34 ± 0.08 vs. 1.40 ± 0.07 m; p = 0.09), DL_H was significantly longer (1.17 ± 0.07 vs. 1.36 ± 0.05 m; p < 0.01). VT_H and VL_H significantly improved after intervention (5.00 ± 0.14 vs. 5.33 ± 0.16 m.s⁻1 and 5.18 ± 0.13 vs. 5.51 ± 0.22 m.s⁻¹, respectively; both p < 0.01). Finally, M_H increased from pre- to post- (52.5 ± 3.8 vs. 54.9 ± 2.1 cm; p < 0.05). A 16-day moderate altitude training camp allowed an elite female 3,000-m steeplechase athlete to improve running velocity through a greater glycolytic—but not aerobic—metabolism.

Concurrent Heat and Intermittent Hypoxic Training: No Additional Performance Benefit Over Temperate Training

PURPOSE

To examine whether concurrent heat and intermittent hypoxic training can improve endurance performance and physiological responses relative to independent heat or temperate interval training.

METHODS

Well-trained male cyclists (N = 29) completed 3 weeks of moderate- to high-intensity interval training (4 × 60 min·wk-1) in 1 of 3 conditions: (1) heat (HOT: 32°C, 50% relative humidity, 20.8% fraction of inspired oxygen, (2) heat + hypoxia (H+H: 32°C, 50% relative humidity, 16.2% fraction of inspired oxygen), or (3) temperate environment (CONT: 22°C, 50% relative humidity, 20.8% fraction of inspired oxygen). Performance 20-km time trials (TTs) were conducted in both temperate (TTtemperate) and assigned condition (TTenvironment) before (base), immediately after (mid), and after a 3-week taper (end). Measures of hemoglobin mass, plasma volume, and blood volume were also assessed.

RESULTS

There was improved 20-km TT performance to a similar extent across all groups in both TTtemperate (mean ±90% confidence interval HOT, -2.8% ±1.8%; H+H, -2.0% ±1.5%; CONT, -2.0% ±1.8%) and TTenvironment (HOT, -3.3% ±1.7%; H+H, -3.1% ±1.6%; CONT, -3.2% ±1.1%). Plasma volume (HOT, 3.8% ±4.7%; H+H, 3.3% ±4.7%) and blood volume (HOT, 3.0% ±4.1%; H+H, 4.6% ±3.9%) were both increased at mid in HOT and H+H over CONT. Increased hemoglobin mass was observed in H+H only (3.0% ±1.8%).

CONCLUSION

Three weeks of interval training in heat, concurrent heat and hypoxia, or temperate environments improve 20-km TT performance to the same extent. Despite indications of physiological adaptations, the addition of independent heat or concurrent heat and hypoxia provided no greater performance benefits in a temperate environment than temperate training alone.

Variability in hemoglobin mass response to altitude training camps

The present study investigated whether athletes can be classified as responders or non-responders based on their individual change in total hemoglobin mass (tHb-mass) following altitude training while also identifying the potential factors that may affect responsiveness to altitude exposure. Measurements were completed with 59 elite endurance athletes who participated in national team altitude training camps. Fifteen athletes participated in the altitude training camp at least twice. Total Hb-mass using a CO rebreathing method and other blood markers were measured before and after a total of 82 altitude training camps (1350-2500 m) in 59 athletes. In 46 (56%) altitude training camps, tHb-mass increased. The amount of positive responses increased to 65% when only camps above 2000 m were considered. From the fifteen athletes who participated in altitude training camps at least twice, 27% always had positive tHb-mass responses, 13% only negative responses, and 60% both positive and negative responses. Logistic regression analysis showed that altitude was the most significant factor explaining positive tHb-mass response. Furthermore, male athletes had greater tHb-mass response than female athletes. In endurance athletes, tHb-mass is likely to increase after altitude training given that hypoxic stimulus is appropriate. However, great inter- and intra-individual variability in tHb-mass response does not support classification of an athlete permanently as a responder or non-responder. This variability warrants efforts to control numerous factors affecting an athlete's response to each altitude training camp.

The Molecular Adaptive Responses of Skeletal Muscle to High-Intensity Exercise/Training and Hypoxia

High-intensity exercise/training, especially interval exercise/training, has gained popularity in recent years. Hypoxic training was introduced to elite athletes half a century ago and has recently been adopted by the general public. In the current review, we have summarised the molecular adaptive responses of skeletal muscle to high-intensity exercise/training, focusing on mitochondrial biogenesis, angiogenesis, and muscle fibre composition. The literature suggests that (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) PGC-1α, vascular endothelial growth factor (VEGF), and hypoxia-inducible factor 1-alpha (HIF1-α) might be the main mediators of skeletal muscle adaptations to high-intensity exercises in hypoxia. Exercise is known to be anti-inflammatory, while the effects of hypoxia on inflammatory signalling are more complex. The anti-inflammatory effects of a single session of exercise might result from the release of anti-inflammatory myokines and other cytokines, as well as the downregulation of Toll-like receptor signalling, while training-induced anti-inflammatory effects may be due to reductions in abdominal and visceral fat (which are main sources of pro-inflammatory cytokines). Hypoxia can lead to inflammation, and inflammation can result in tissue hypoxia. However, the hypoxic factor HIF1-α is essential for preventing excessive inflammation. Disease-induced hypoxia is related to an upregulation of inflammatory signalling, but the effects of exercise-induced hypoxia on inflammation are less conclusive. The effects of high-intensity exercise under hypoxia on skeletal muscle molecular adaptations and inflammatory signalling have not been fully explored and are worth investigating in future studies. Understanding these effects will lead to a more comprehensive scientific basis for maximising the benefits of high-intensity exercise.

Nutrition and Altitude: Strategies to Enhance Adaptation, Improve Performance and Maintain Health: A Narrative Review

Training at low to moderate altitudes (~ 1600-2400 m) is a common approach used by endurance athletes to provide a distinctive environmental stressor to augment training stimulus in the anticipation of increasing subsequent altitude- and sea-level-based performance. Despite some scientific progress being made on the impact of various nutrition-related changes in physiology and associated interventions at mountaineering altitudes (> 3000 m), the impact of nutrition and/or supplements on further optimization of these hypoxic adaptations at low-moderate altitudes is only an emerging topic. Within this narrative review we have highlighted six major themes involving nutrition: altered energy availability, iron, carbohydrate, hydration, antioxidant requirements and various performance supplements. Of these issues, emerging data suggest that particular attention be given to the potential risk for poor energy availability and increased iron requirements at the altitudes typical of elite athlete training (~ 1600-2400 m) to interfere with optimal adaptations. Furthermore, the safest way to address the possible increase in oxidative stress associated with altitude exposure is via the consumption of antioxidant-rich foods rather than high-dose antioxidant supplements. Meanwhile, many other important questions regarding nutrition and altitude training remain to be answered. At the elite level of sport where the differences between winning and losing are incredibly small, the strategic use of nutritional interventions to enhance the adaptations to altitude training provides an important consideration in the search for optimal performance.

Contemporary Periodization of Altitude Training for Elite Endurance Athletes: A Narrative Review

Since the 1960s there has been an escalation in the purposeful utilization of altitude to enhance endurance athletic performance. This has been mirrored by a parallel intensification in research pursuits to elucidate hypoxia-induced adaptive mechanisms and substantiate optimal altitude protocols (e.g., hypoxic dose, duration, timing, and confounding factors such as training load periodization, health status, individual response, and nutritional considerations). The majority of the research and the field-based rationale for altitude has focused on hematological outcomes, where hypoxia causes an increased erythropoietic response resulting in augmented hemoglobin mass. Hypoxia-induced non-hematological adaptations, such as mitochondrial gene expression and enhanced muscle buffering capacity may also impact athletic performance, but research in elite endurance athletes is limited. However, despite significant scientific progress in our understanding of hypobaric hypoxia (natural altitude) and normobaric hypoxia (simulated altitude), elite endurance athletes and coaches still tend to be trailblazers at the coal face of cutting-edge altitude application to optimize individual performance, and they already implement novel altitude training interventions and progressive periodization and monitoring approaches. Published and field-based data strongly suggest that altitude training in elite endurance athletes should follow a long- and short-term periodized approach, integrating exercise training and recovery manipulation, performance peaking, adaptation monitoring, nutritional approaches, and the use of normobaric hypoxia in conjunction with terrestrial altitude. Future research should focus on the long-term effects of accumulated altitude training through repeated exposures, the interactions between altitude and other components of a periodized approach to elite athletic preparation, and the time course of non-hematological hypoxic adaptation and de-adaptation, and the potential differences in exercise-induced altitude adaptations between different modes of exercise.

Effect of an Eleven-Day Altitude Training Program on Aerobic and Anaerobic Performance in Adolescent Runners

Background and Objectives: We evaluated the effect of an eleven-day altitude training camp on aerobic and anaerobic fitness in trained adolescent runners. Materials and Methods: Twenty adolescent (14–18 yrs) middle- and long-distance runners (11 males and 9 females; 16.7 ± 0.8 yrs), with at least two years of self-reported consistent run training, participated in this study. Eight of the subjects (4 females/4 males) constituted the control group, whereas twelve subjects (5 females/7 males) took part in a structured eleven-day altitude training camp, and training load was matched between groups. Primary variables of interest included changes in aerobic (VO₂max) and anaerobic (30 s Wingate test) power. We also explored the relationships between running velocity and blood lactate levels before and after the altitude training camp. Results: Following 11 days of altitude training, desirable changes (p < 0.01) in VO₂max (+13.6%), peak relative work rate (+9.6%), and running velocity at various blood lactate concentrations (+5.9%–9.6%) were observed. Meanwhile, changes in Wingate anaerobic power (+5.1%) were statistically insignificant (p > 0.05). Conclusions: Short duration altitude appears to yield meaningful improvements in aerobic but not anaerobic power in trained adolescent endurance runners.

An Updated Panorama of "Living Low-Training High" Altitude/Hypoxic Methods

With minimal costs and travel constraints for athletes, the “living low-training high” (LLTH) approach is becoming an important intervention for modern sport. The popularity of the LLTH model of altitude training is also associated with the fact that it only causes a slight disturbance to athletes' usual daily routine, allowing them to maintain their regular lifestyle in their home environment. In this perspective article, we discuss the evolving boundaries of the LLTH paradigm and its practical applications for athletes. Passive modalities include intermittent hypoxic exposure at rest (IHE) and Ischemic preconditioning (IPC). Active modalities use either local [blood flow restricted (BFR) exercise] and/or systemic hypoxia [continuous low-intensity training in hypoxia (CHT), interval hypoxic training (IHT), repeated-sprint training in hypoxia (RSH), sprint interval training in hypoxia (SIH) and resistance training in hypoxia (RTH)]. A combination of hypoxic methods targeting different attributes also represents an attractive solution. In conclusion, a growing number of LLTH altitude training methods exists that include the application of systemic and local hypoxia stimuli, or a combination of both, for performance enhancement in many disciplines.

Understanding placebo and nocebo effects in the context of sport: A psychological perspective

Research over the past 15 years on the placebo effect has substantiated its contribution to the efficacy of established treatments for a range of clinical conditions and identified its underlying mechanisms. There is also evidence that placebo effects contribute to the performance benefits of many ergogenic aids, and that performance can worsen when dummy treatments are associated with expectations of a harmful outcome (i.e. nocebo effect). Unfortunately, the bulk of sport research involving placebos and nocebos continues to be hampered by outdated definitions and conceptualizations of placebo effects and their mechanisms. This has implications not only for research but also application, as nearly 50% of athletes report experiencing a beneficial placebo effect, and a similar proportion of coaches report providing placebos to their athletes. The objective of this paper is to attempt to stimulate research by presenting updated definitions of placebo and nocebo effects in the context of sport, describing their major mechanisms and, highlighting the importance of the psychosocial context on placebo effects in the sport setting.

Hematological status and endurance performance predictors after low altitude training supported by normobaric hypoxia: a double-blind, placebo controlled study

The benefits of altitude/hypoxic training for sea level performance are still under debate. This study examined the effects of low altitude training supported by normobaric hypoxia on hematological status and endurance performance predictors in elite female cyclists. Twenty-two female cyclists trained for 3 weeks at low altitude (<1100 m) and 2 weeks near sea level. During the first 3 weeks, 15 subjects stayed in hypoxic rooms simulating an altitude of 2200 m (+NH group, n = 8) or 1000 m (placebo group, n = 7), and 7 (control group) stayed in regular rooms. Significant increases in total hemoglobin mass (tHb-mass: p = 0.008, p = 0.025), power at 4 mmol·l^-1 lactate (PAT4: p = 0.004, p = 0.005) (in absolute and relative values, respectively) and maximal power (PF: p = 0.034) (in absolute values) were observed. However, these effects were not associated with normobaric hypoxia. Changes in tHb-mass were not associated with initial concentrations of ferritin or transferrin receptor, whereas changes in relative tHb-mass (r = -0.53, p = 0.012), PF (r = -0.53, p = 0.01) and PAT4 (r = -0.65, p = 0.001) were inversely correlated with initial values. Changes in tHb-mass and PAT4 were positively correlated (r = 0.50, p = 0.017; r = 0.47, p = 0.028). Regardless of normobaric hypoxia application, low altitude training followed by sea-level training might improve hematological status in elite female cyclists, especially with relatively low initial values of tHb-mass, which could translate into enhanced endurance performance.

Single versus Split Dose of Iron Optimizes Hemoglobin Mass Gains at 2106 m Altitude

PURPOSE

To determine if a single versus a split equivalent daily dose of elemental iron was superior for hemoglobin mass (Hbmass) gains at altitude while minimizing gastrointestinal (GI) discomfort.

METHODS

Twenty-four elite runners attended a 3.1 ± 0.3 wk training camp (Flagstaff, AZ; 2106 m). A two-group design, randomized and stratified to baseline Hbmass, sex, and ferritin (>30 μ·L), was implemented daily as: 1) single dose of 1 × 200 mg (PM only, SINGLE) versus 2) split dose of 2 × 100 mg (AM and PM; SPLIT) elemental iron (ferrous fumarate). The Hbmass and venipuncture assessments were completed upon arrival and departure (±2 d) from camp for ferritin, hepcidin, and erythroferrone (ERFE) concentrations. Validated food frequency, GI distress, menstrual blood loss (MBL) and training questionnaires were implemented throughout. Univariate analysis was used to compare Hbmass, with baseline ferritin, dietary iron intake, MBL, and training volume used as covariates.

RESULTS

Both conditions increased Hbmass from baseline (P < 0.05), with SINGLE (867.3 ± 47.9 g) significantly higher than SPLIT (828.9 ± 48.9 g) (P = 0.048). The GI scores were worse in SINGLE for weeks 1 and 2 combined (SINGLE, 18.0 ± 6.7 points; SPLIT, 11.3 ± 6.9 points; P = 0.025); however, GI scores improved by week 3, resulting in no between-group differences (P = 0.335). Hepcidin significantly decreased over time (P = 0.043) in SINGLE, with a nonsignificant decrease evident in SPLIT (~22%). ERFE significantly decreased in both groups (~28.5%; P < 0.05). No between-group differences existed for ERFE, hepcidin, food frequency, MBL, or daily training outcomes (P > 0.05).

CONCLUSIONS

A single nightly 200-mg dose of elemental iron was superior to a split dose for optimizing Hbmass changes at altitude in runners over an approximately 3-wk training camp.

Intermittent Hypoxic Training at Lactate Threshold Intensity Improves Aiming Performance in Well-Trained Biathletes with Little Change of Cardiovascular Variables

The main objective of this research was to evaluate the efficacy of intermittent hypoxic training (IHT) on aiming performance and aerobic capacity in biathletes. Fourteen male biathletes were randomly divided into a hypoxia group (H) (n = 7), which trained three times per week in a normobaric hypoxic environment (FiO₂ = 16.5%, 2000 m a.s.l.) with lactate threshold intensity (LT) determined in hypoxia, and a control group (C) (n = 7), which exercised under normoxic conditions with LT intensity determined in normoxia. The training program included three weekly microcycles, followed by three days of recovery. The main part of the interval workout consisted of four 7 min (1^st week), 8 min (2^nd week), or 9 min (3^rd week) running bouts at treadmill separated by 2 minutes of active recovery. After the warm-up and during the rest between the bouts, the athletes performed aiming to the target in the standing position with a sporting rifle (20 s). The results showed that the IHT caused a significant (p < 0.05) increase in retention time in the target at rest (RT9_rest) by 14.4% in hypoxia, whereas RT postincremental test (RT9_post) increased by 27.4% in normoxia and 26.7% in hypoxia. No significant changes in this variable were found in group C. Additionally, the capillary oxygen saturation at the end of the maximal effort (SO_{2capillary max}) in hypoxia increased significantly (p < 0.001) by ∼4% after IHT. The maximal workload during the incremental test (WR_max) in normoxia also increased significantly (p < 0.001) by 6.3% after IHT. Furthermore, in absolute and relative values of VO_2max in normoxia, there was a propensity (p < 0.07) for increasing this value by 5% in group H. In conclusion, the main findings of this study showed a significant improvement in resting and postexercise aiming performance in normoxia and hypoxia. Furthermore, the results demonstrated beneficial effects of the IHT protocol on aerobic capacity of biathletes.

Comparison of the Effectiveness of High-Intensity Interval Training in Hypoxia and Normoxia in Healthy Male Volunteers: A Pilot Study

Aims

The study investigated the effect of high-intensity interval training in hypoxia and normoxia on serum concentrations of proangiogenic factors, nitric oxide, and inflammatory responses in healthy male volunteers.

Methods

Twelve physically active male subjects completed a high-intensity interval training (HIIT) in normoxia (NorTr) and in normobaric hypoxia (HypTr) (FiO₂ = 15.2%). The effects of HIIT in hypoxia and normoxia on maximal oxygen uptake, hypoxia-inducible factor-1-alpha, vascular endothelial growth factor, nitric oxide, and cytokines were analyzed.

Results

HIIT in hypoxia significantly increases maximal oxygen uptake (p=0.01) levels compared to pretraining levels. Serum hypoxia-inducible factor-1 (p=0.01) and nitric oxide levels (p=0.05), vascular endothelial growth factor (p=0.04), and transforming growth factor-β (p=0.01) levels were increased in response to exercise test after hypoxic training. There was no effect of training conditions for serum baseline angiogenic factors and cytokines (p > 0.05) with higher HIF-1α and NO levels after hypoxic training compared to normoxic training (F = 9.1; p < 0.01 and F = 5.7; p < 0.05, respectively).

Conclusions

High-intensity interval training in hypoxia seems to induce beneficial adaptations to exercise mediated via a significant increase in the serum concentrations of proangiogenic factors and serum nitric oxide levels compared to the same training regimen in normoxia.

Effects of Repetitive Altitude Training on Salivary Immunoglobulin A Secretion in Collegiate Swimmers

Background

Altitude training has often been conducted just before main competition games in many sports. An increase in the frequency of upper respiratory tract infections and gastrointestinal infections due to an altitude-induced suppression of the immune system has been reported after altitude training. Salivary secretory immunoglobulin A (SIgA) is the major immunoglobulin of the mucosal immune system. A suppressive effect of heavy training on SIgA has been reported. However, little is known regarding the effects of repetitive altitude training and hypoxic exposure on SIgA. The objective of this study was to evaluate the changes in SIgA in swimmers undergoing repetitive altitude training at 1,900 m.

Methods

Nine collegiate swimmers who experienced their first altitude training experience (FT group) were compared to nine swimmers who experienced repetitive training (RT group) and non-training subjects (Con group). Saliva was collected before ascent and eight times every 2 days during altitude training. SIgA levels were measured by enzyme-linked immunosorbent assays.

Results

Compared to the Con group, SIgA levels and the secretion velocity were decreased after ascent and were slowly restored in both the FT and RT groups. The chronological trends in SIgA levels were similar, even though the decline in SIgA levels in the FT group was larger than that in the RT group.

Conclusion

Altitude training and experience with altitude training may be one of the factors influencing SIgA.

Altitude Training and Recombinant Human Erythropoietin: Considerations for Doping Detection

The benefit of training at altitude to enhance exercise performance remains equivocal although the most widely accepted approach is one where the athletes live and perform lower-intensity running at approximately 2300 m with high-intensity training at approximately 1250 m. The idea is that this method maintains maximal augmentations in total hemoglobin mass while reducing the performance impairment of high-intensity sessions performed at moderate altitude and thus preventing any detraining that can occur when athletes live and train at moderate altitude. This training regimen, however, is not universally accepted and some argue that the performance enhancement is due to placebo and training camp effects. Altitude training may affect an athlete's hematological parameters in ways similar to those observed following blood doping. Current methods of detection appear insufficient to differentiate between altitude training and blood doping making the interpretation of an athlete's biological passport difficult. Further research is required to determine the optimal method for altitude training and to enhance current detection methods to be able to differentiate better blood doping and altitude exposure.

Training to Compete at Altitude:Natural Altitude or Simulated Live High:Train Low?

PURPOSE

To compare the effects of natural altitude training (NAT) and simulated (SIM) live high:train low altitude training on road-race walking performance (min), as well as treadmill threshold walking speed (km·h^-1) at 4 mmol·L^-1 and maximal oxygen consumption, at 1380 m.

METHODS

Twenty-two elite-level male (n = 15) and female (n = 7) race walkers completed 14 d of NAT at 1380 m (n = 7), SIM live high:train low at 3000:600 m (n = 7), or control conditions (600-m altitude; CON, n = 8). All preintervention and postintervention testing procedures were conducted at 1380 m and consisted of an incremental treadmill test, completed prior to a 5 × 2-km road-race walking performance test. Differences between groups were analyzed via mixed-model analysis of variance and magnitude-based inferences, with a substantial change detected with >75% likelihood of exceeding the smallest worthwhile change.

RESULTS

The improvement in total performance time for the 5 × 2-km test in NAT was not substantially different from SIM but was substantially greater (85% likely) than CON. The improvement in percentage decrement in the 5 × 2-km performance test in NAT was greater than in both SIM (93% likely) and CON (93% likely). The increase in maximal oxygen consumption was substantially greater (91% likely) in NAT than in SIM. Improvement in threshold walking speed was substantially greater than CON for both SIM (91% likely) and NAT (90% likely).

CONCLUSIONS

Both NAT and SIM may allow athletes to achieve reasonable acclimation prior to competition at low altitude.