Current trends in altitude training

GXT responses in altitude-acclimatized cyclists during sea-level simulation

PURPOSE

This study examined the effects of gender on graded exercise stress test (GXT) response in moderate-altitude (MA)-acclimatized cyclists during sea-level (SL) simulation. It was hypothesized that alterations in arterial saturation would relate to changes in VO2peak.

METHODS

Twenty competitive cyclists (12 males, 8 females) who were residents of MA locations underwent two randomized bicycle GXTs: one under local normoxic hypobaria, and the other under simulated SL conditions.

RESULTS

Under the SL condition, the cyclists demonstrated a significant increase (2-3%) in absolute and relative VO2peak, improved (4%) economy at lactate threshold (LT), and time-adjusted peak power (7%); the range of improvement between individuals varied from -6% to +25%. Simulated SL also resulted in a greater arterial saturation (S(a)O2) at rest and VO2peak, and significantly less desaturation (4 vs 8%) from rest to VO2peak. The individual variability in the change (Delta) in VO2peak was not significantly correlated to SL S(a)O2 or any other S(a)O2 variable analyzed, regardless of whether we examined each gender individually or combined. Significant correlations were found between Delta-peak power and Delta-economy as well as Delta-VO2peak and Delta-GXT time. These correlations as well as degree of improvement varied by gender.

CONCLUSIONS

These data suggest that chronic residence at MA may attenuate the occurrence of exercise-induced arterial hypoxemia and eliminate the relationship between S(a)O2 and Delta-VO2peak that has been reported among SL residents acutely exposed to altitude. Additionally, the improvements that occur in predictors of aerobic performance when MA residents are exposed acutely to SL conditions have a large degree of individual variability, and the mechanism(s) for improvement may vary by gender.

Effect of hypoxic "dose" on physiological responses and sea-level performance

Live high-train low (LH+TL) altitude training was developed in the early 1990s in response to potential training limitations imposed on endurance athletes by traditional live high-train high (LH+TH) altitude training. The essence of LH+TL is that it allows athletes to "live high" for the purpose of facilitating altitude acclimatization, as manifest by a profound and sustained increase in endogenous erythropoietin (EPO) and ultimately an augmented erythrocyte volume, while simultaneously allowing athletes to "train low" for the purpose of replicating sea-level training intensity and oxygen flux, thereby inducing beneficial metabolic and neuromuscular adaptations. In addition to "natural/terrestrial" LH+TL, several simulated LH+TL devices have been developed to conveniently bring the mountain to the athlete, including nitrogen apartments, hypoxic tents, and hypoxicator devices. One of the key questions regarding the practical application of LH+TL is, what is the optimal hypoxic dose needed to facilitate altitude acclimatization and produce the expected beneficial physiological responses and sea-level performance effects? The purpose of this paper is to objectively answer that question, on the basis of an extensive body of research by our group in LH+TL altitude training. We will address three key questions: 1) What is the optimal altitude at which to live? 2) How many days are required at altitude? and 3) How many hours per day are required? On the basis of consistent findings from our research group, we recommend that for athletes to derive the physiological benefits of LH+TL, they need to live at a natural elevation of 2000-2500 m for >or=4 wk for >or=22 h.d(-1).

Introduction to altitude/hypoxic training symposium

Altitude/hypoxic training has traditionally been an intriguing and controversial area of research and sport performance. This controversial aspect was evident recently in the form of scholarly debates in highly regarded professional journals, as well as the World Anti-Doping Agency's (WADA) consideration of placing "artificially-induced hypoxic conditions" on the 2007 Prohibited List of Substances/Methods. In light of the ongoing controversy surrounding altitude/hypoxic training, this symposium was organized with the following objectives in mind: 1) to examine the primary physiological responses and underlying mechanisms associated with altitude/hypoxic training, including the influence of genetic predisposition; 2) to present evidence supporting the effect of altitude/hypoxic acclimatization on both hematological and nonhematological markers, including erythrocyte volume, skeletal muscle-buffering capacity, hypoxic ventilatory response, and physiological efficiency/economy; 3) to evaluate the efficacy of several contemporary simulated altitude modalities and training strategies, including hypoxic tents, nitrogen apartments, and intermittent hypoxic exposure (IHE) or training, and to address the legal and ethical issues associated with the use of simulated altitude; and 4) to describe different altitude/hypoxic training strategies used by elite-level athletes, including Olympians and military special forces. In addressing these objectives, papers will be presented on the topics of: 1) effect of hypoxic "dose" on physiological responses and sea-level performance (Drs. Benjamin Levine and James Stray-Gundersen), 2) nonhematological mechanisms of improved performance after hypoxic exposure (Dr. Christopher Gore), 3) application of altitude/hypoxic training by elite athletes (Dr. Randall Wilber), and 4) military applications of hypoxic training (Dr. Stephen Muza).

Changes in sleep quality of athletes under normobaric hypoxia equivalent to 2,000-m altitude: a polysomnographic study

This study evaluated the sleep quality of athletes in normobaric hypoxia at a simulated altitude of 2,000 m. Eight male athletes slept in normoxic condition (NC) and hypoxic conditions equivalent to those at 2,000-m altitude (HC). Polysomnographic recordings of sleep included the electroencephalogram (EEG), electrooculogram, chin surface electromyogram, and electrocardiogram. Thoracic and abdominal motion, nasal and oral airflow, and arterial blood oxygen saturation (SaO2) were also recorded. Standard visual sleep stage scoring and fast Fourier transformation analyses of the EEG were performed on 30-s epochs. Subjective sleepiness and urinary catecholamines were also monitored. Mean SaO2 decreased and respiratory disturbances increased with HC. The increase in respiratory disturbances was significant, but the increase was small and subclinical. The duration of slow-wave sleep (stage 3 and 4) and total delta power (<3 Hz) of the all-night non-rapid eye movement sleep EEG decreased for HC compared with NC. Subjective sleepiness and amounts of urinary catecholamines did not differ between the conditions. These results indicate that acute exposure to normobaric hypoxia equivalent to that at 2,000-m altitude decreased slow-wave sleep in athletes, but it did not change subjective sleepiness or amounts of urinary catecholamines.

Live High + Train Low: Thinking in Terms of an Optimal Hypoxic Dose

“Live high-train low” (LH+TL) altitude training allows athletes to “live high” for the purpose of facilitating altitude acclimatization, as characterized by a significant and sustained increase in endogenous erythropoietin and subsequent increase in erythrocyte volume, while simultaneously enabling them to “train low” for the purpose of replicating sea-level training intensity and oxygen flux, thereby inducing beneficial metabolic and neuromuscular adaptations. In addition to natural/terrestrial LH+TL, several simulated LH+TL devices have been developed including nitrogen apartments, hypoxic tents, and hypoxicator devices. One of the key issues regarding the practical application of LH+TL is what the optimal hypoxic dose is that is needed to facilitate altitude acclimatization and produce the expected beneficial physiological responses and sea-level performance effects. The purpose of this review is to examine this issue from a research-based and applied perspective by addressing the following questions: What is the optimal altitude at which to live, how many days are required at altitude, and how many hours per day are required? It appears that for athletes to derive the hematological benefits of LH+TL while using natural/terrestrial altitude, they need to live at an elevation of 2000 to 2500 m for >4 wk for >22 h/d. For athletes using LH+TL in a simulated altitude environment, fewer hours (12-16 h) of hypoxic exposure might be necessary, but a higher elevation (2500 to 3000 m) is required to achieve similar physiological responses.

Application of Altitude/Hypoxic Training by Elite Athletes

At the Olympic level, differences in performance are typically less than 0.5%. This helps explain why many contemporary elite endurance athletes in summer and winter sport incorporate some form of altitude/hypoxic training within their year-round training plan, believing that it will provide the "competitive edge" to succeed at the Olympic level. The purpose of this paper is to describe the practical application of altitude/hypoxic training as used by elite athletes. Within the general framework of the paper, both anecdotal and scientific evidence will be presented relative to the efficacy of several contemporary altitude/hypoxic training models and devices currently used by Olympic-level athletes for the purpose of legally enhancing performance. These include the three primary altitude/hypoxic training models: 1) live high+train high (LH+TH), 2) live high+train low (LH+TL), and 3) live low+train high (LL+TH). The LH+TL model will be examined in detail and will include its various modifications: natural/terrestrial altitude, simulated altitude via nitrogen dilution or oxygen filtration, and hypobaric normoxia via supplemental oxygen. A somewhat opposite approach to LH+TL is the altitude/hypoxic training strategy of LL+TH, and data regarding its efficacy will be presented. Recently, several of these altitude/hypoxic training strategies and devices underwent critical review by the World Anti-Doping Agency (WADA) for the purpose of potentially banning them as illegal performance-enhancing substances/methods. This paper will conclude with an update on the most recent statement from WADA regarding the use of simulated altitude devices.

Effects of intermittent hypoxic training on cycling performance in well-trained athletes

This study aimed to investigate the effects of a short-term period of intermittent hypoxic training (IHT) on cycling performance in athletes. Nineteen participants were randomly assigned to two groups: normoxic (NT, n = 9) and intermittent hypoxic training group (IHT, n = 10). A 3-week training program (5 x 1 h-1 h 30 min per week) was completed. Training sessions were performed in normoxia (approximately 30 m) or hypoxia (simulated altitude of 3,000 m) for NT and IHT group, respectively. Each subject performed before (W0) and after (W4) the training program, three cycling tests including an incremental test to exhaustion in normoxia and hypoxia for determination of maximal aerobic power (VO2max) and peak power output (PPO) as well as a 10-min cycle time trial in normoxia (TT) to measure the average power output (P(aver)). No significant difference in VO2max was observed between the two training groups before or after the training period. When measured in normoxia, the PPO significantly increased (P < 0.05) by 7.2 and 6.6% in NT and IHT groups, respectively. However, only the IHT group significantly improved (11.3%; P < 0.05) PPO when measured in hypoxia. The NT group improved (P < 0.05) P(aver) in TT by 8.1%, whereas IHT group did not show any significant difference. Intermittent training performed in hypoxia was less efficient for improving endurance performance at sea level than similar training performed in normoxia. However, IHT has the potential to assist athletes in preparation for competition at altitude.

Oxygen breathing may be a cheaper and safer alternative to exogenous erythropoietin (EPO)

Erythropoietin (EPO) is a glycoprotein hormone produced by renal tissue in response to hypoxia; EPO functions as a cytokine to precursor cells produced by the bone marrow, stimulating red blood cell production. Erythropoiesis stimulating agents (ESAs) are manufactured molecules designed to mimic the ability of endogenous EPO to bind to EPO receptors and increase red blood cell production. To achieve desired dosing schedules and avoid the need for blood transfusions, oncologists have become increasingly reliant on ESAs to counter the anemia often experienced during chemotherapy. In recent years, significant concerns have been raised about the safety of ESAs, including the possibility of increased cardiovascular events and even increased tumor growth and accelerated mortality in cancer patients. ESAs also contribute significantly to the expense of chemotherapy, rendering them unavailable to some patients and available to others only upon achieving insurance-mandated levels of anemia. A recently discovered "normobaric oxygen paradox" demonstrates that renal tissue can be stimulated to increase EPO production via a simple pattern of oxygen breathing at normal atmospheric pressures. This leads directly to the hypothesis that oxygen breathing may provide chemotherapy patients with a convenient and inexpensive alternative to ESAs. Stimulating endogenous EPO production eliminates the small risk of immune system reaction associated with ESAs. Further, the endogenous physiological EPO doses provided by this method may be safer, in terms of cancer mortality, than the exogenous pharmacological doses inherent in ESA administration. A single patient test case is presented to support the hypothesis that normobaric oxygen breathing can be an effective replacement for ESAs in treating chemotherapy-induced anemia. In this case, a stage III breast cancer patient undergoing dose-dense AC+T chemotherapy obtained a clear response equivalent to ESA treatment by using a pattern of simple oxygen breathing.

Current anti-doping policy: a critical appraisal

BACKGROUND

Current anti-doping in competitive sports is advocated for reasons of fair-play and concern for the athlete's health. With the inception of the World Anti Doping Agency (WADA), anti-doping effort has been considerably intensified. Resources invested in anti-doping are rising steeply and increasingly involve public funding. Most of the effort concerns elite athletes with much less impact on amateur sports and the general public.

DISCUSSION

We review this recent development of increasingly severe anti-doping control measures and find them based on questionable ethical grounds. The ethical foundation of the war on doping consists of largely unsubstantiated assumptions about fairness in sports and the concept of a "level playing field". Moreover, it relies on dubious claims about the protection of an athlete's health and the value of the essentialist view that sports achievements reflect natural capacities. In addition, costly antidoping efforts in elite competitive sports concern only a small fraction of the population. From a public health perspective this is problematic since the high prevalence of uncontrolled, medically unsupervised doping practiced in amateur sports and doping-like behaviour in the general population (substance use for performance enhancement outside sport) exposes greater numbers of people to potential harm. In addition, anti-doping has pushed doping and doping-like behaviour underground, thus fostering dangerous practices such as sharing needles for injection. Finally, we argue that the involvement of the medical profession in doping and anti-doping challenges the principles of non-maleficience and of privacy protection. As such, current anti-doping measures potentially introduce problems of greater impact than are solved, and place physicians working with athletes or in anti-doping settings in an ethically difficult position. In response, we argue on behalf of enhancement practices in sports within a framework of medical supervision.

SUMMARY

Current anti-doping strategy is aimed at eradication of doping in elite sports by means of all-out repression, buttressed by a war-like ideology similar to the public discourse sustaining international efforts against illicit drugs. Rather than striving for eradication of doping in sports, which appears to be an unattainable goal, a more pragmatic approach aimed at controlled use and harm reduction may be a viable alternative to cope with doping and doping-like behaviour.

Erythropoietin regulations in humans under different environmental and experimental conditions

In the adult human, the kidney is the main organ for the production and release of erythropoietin (EPO). EPO is stimulating erythropoiesis by increasing the proliferation, differentiation and maturation of the erythroid precursors. In the last decades, enormous efforts were made in the purification, molecular encoding and description of the EPO gene. This led to an incredible increase in the understanding of the EPO-feedback-regulation loop at a molecular level, especially the oxygen-dependent EPO gene expression, a key function in the regulation loop. However, studies in humans at a systemic level are still very scanty. Therefore, it is the purpose of the present review to report on the main recent investigations on EPO production and release in humans under different environmental and experimental conditions, including: (i) studies on EPO circadian, monthly and even annual variations, (ii) studies in connection with short-, medium- and long-term exercise at sea-level which will be followed (iii) by studies performed at moderate and high altitude.

Biochemistry, physiology, and complications of blood doping: facts and speculation

Competition is a natural part of human nature. Techniques and substances employed to enhance athletic performance and to achieve unfair success in sport have a long history, and there has been little knowledge or acceptance of potential harmful effects. Among doping practices, blood doping has become an integral part of endurance sport disciplines over the past decade. The definition of blood doping includes methods or substances administered for non-medical reasons to healthy athletes for improving aerobic performance. It includes all means aimed at producing an increased or more efficient mechanism of oxygen transport and delivery to peripheral tissues and muscles. The aim of this review is to discuss the biochemistry, physiology, and complications of blood doping and to provide an update on current antidoping policies.

Effects of intermittent hypoxic training on amino and fatty acid oxidative combustion in human permeabilized muscle fibers

The effects of concurrent hypoxic/endurance training on mitochondrial respiration in permeabilized fibers in trained athletes were investigated. Eighteen endurance athletes were divided into two training groups: normoxic (Nor, n = 8) and hypoxic (H, n = 10). Three weeks (W1-W3) of endurance training (5 sessions of 1 h to 1 h and 30 min per week) were completed. All training sessions were performed under normoxic [160 Torr inspired Po(2) (Pi(O(2)))] or hypoxic conditions ( approximately 100 Torr Pi(O(2)), approximately 3,000 m) for Nor and H group, respectively, at the same relative intensity. Before and after the training period, an incremental test to exhaustion in normoxia was performed, muscle biopsy samples were taken from the vastus lateralis, and mitochondrial respiration in permeabilized fibers was measured. Peak power output (PPO) increased by 7.2% and 6.6% (P < 0.05) for Nor and H, respectively, whereas maximal O(2) uptake (Vo(2 max)) remained unchanged: 58.1 +/- 0.8 vs. 61.0 +/- 1.2 ml.kg(-1).min(-1) and 58.5 +/- 0.7 vs. 58.3 +/- 0.6 ml.kg(-1).min(-1) for Nor and H, respectively, between pretraining (W0) and posttraining (W4). Maximal ADP-stimulated mitochondrial respiration significantly increased for glutamate + malate (6.27 +/- 0.37 vs. 8.51 +/- 0.33 mumol O(2).min(-1).g dry weight(-1)) and significantly decreased for palmitate + malate (3.88 +/- 0.23 vs. 2.77 +/- 0.08 mumol O(2).min(-1).g dry weight(-1)) in the H group. In contrast, no significant differences were found for the Nor group. The findings demonstrate that 1) a 3-wk training period increased the PPO at sea level without any changes in Vo(2 max), and 2) a 3-wk hypoxic exercise training seems to alter the intrinsic properties of mitochondrial function, i.e., substrate preference.

ACE gene polymorphism and erythropoietin in endurance athletes at moderate altitude

PURPOSE

To determine the role of the ACE (I/D) gene polymorphism on erythropoietic response in endurance athletes after natural exposure to moderate altitude.

METHODS

Erythropoietic activity was measured in 63 male endurance athletes following natural exposure to moderate altitude (2200 m) during 48 h. Erythropoietin (EPO) levels and hemoglobin (Hb) concentrations were measured at baseline and 12, 24, and 48 h after reaching the set altitude. Reticulocyte counts were determined at baseline and 48 h thereafter. Subjects were grouped into two groups (responders and nonresponders) based on significant increase in EPO levels (median: > 16.5 ng x m(-1)) after 24 h at altitude. ACE gene polymorphism was ascertained by polymerase chain reaction (DD, 31 (49%); ID, 24 (38%); II, 8 (13%)).

RESULTS

Overall, EPO levels significantly increased at 12 (70%; P = 0.0001) and 24 h (72%; P = 0.0001) above baseline concentration following exposure to 2200 m. Thereafter, EPO concentration decreased at 48 h, but a significant increase in Hb levels (4.6 +/- 4%; P = 0.0001) and reticulocyte count (50.5 +/- 79%; P = 0.0001) was observed at the end of the experiment, suggesting negative feedback. There were no significant differences in EPO and Hb concentration profiles between subjects with DD genotype and those with other genotypes (ID/II). Moreover, responders (N = 42; DD, 50%; ID/II, 50%) and nonresponders (N = 21; DD, 48%; ID/II, 52%) showed a similar erythropoietic profile during the experiment and the ACE gene polymorphism did not influence the time course of the erythropoietic response.

CONCLUSIONS

The ACE gene polymorphism does not influence erythropoietic activity in endurance athletes after short-term exposure to moderate altitude.

[Physiological aspects of altitude training and the use of altitude simulators]

Altitude training in various forms is widely practiced by athletes and coaches in an attempt to improve sea level endurance. Training at high altitude may improve performance at sea level through altitude acclimatisation, which improves oxygen transport and/or utilisation, or through hypoxia, which intensifies the training stimulus. This basic physiological aspect allows three training modalities: live high and train high (classic high-altitude training), live low and train high (training through hypoxia), and live high and train low (the new trend). In an effort to reduce the financial and logistical challenges of travelling to high-altitude training sites, scientists and manufactures have developed artificial high-altitude environments, which simulate the hypoxic conditions of moderate altitude (2000-3000 meters). Endurance athletes from many sports have recently started using nitrogen environments, or hypoxic rooms and tents as part of their altitude training programmes. The results of controlled studies on these modalities of high-altitude training, their practical approach, and ethics are summarised.

Dose-Response of Altitude Training: How Much Altitude is Enough?

Altitude training continues to be a key adjunctive aid for the training of competitive athletes throughout the world. Over the past decade, evidence has accumulated from many groups of investigators that the "living high--training low" approach to altitude training provides the most robust and reliable performance enhancements. The success of this strategy depends on two key features: 1) living high enough, for enough hours per day, for a long enough period of time, to initiate and sustain an erythropoietic effect of high altitude; and 2) training low enough to allow maximal quality of high intensity workouts, requiring high rates of sustained oxidative flux. Because of the relatively limited access to environments where such a strategy can be practically applied, numerous devices have been developed to "bring the mountain to the athlete," which has raised the key issue of the appropriate "dose" of altitude required to stimulate an acclimatization response and performance enhancement. These include devices using molecular sieve technology to provide a normobaric hypoxic living or sleeping environment, approaches using very high altitudes (5,500m) for shorter periods of time during the day, and "intermittent hypoxic training" involving breathing very hypoxic gas mixtures for alternating 5 minutes periods over the course of 60-90 minutes. Unfortunately, objective testing of the strategies employing short term (less than 4 hours) normobaric or hypobaric hypoxia has failed to demonstrate an advantage of these techniques. Moreover individual variability of the response to even the best of living high--training low strategies has been great, and the mechanisms behind this variability remain obscure. Future research efforts will need to focus on defining the optimal dosing strategy for these devices, and determining the underlying mechanisms of the individual variability so as to enable the individualized "prescription" of altitude exposure to optimize the performance of each athlete.

Effects of short-term normobaric hypoxia on haematology, muscle phenotypes and physical performance in highly trained athletes

This study aimed to determine the impact of short-term normobaric hypoxia on physiology and performance in highly trained athletes. Twelve (7 male and 5 female) athletes were randomly assigned into two groups and spent 8 h per night for two consecutive nights a week over 3 weeks under either short-term normobaric hypoxia (simulating 3636 m altitude, inspired O2=13%) or in normobaric normoxia in a single-blind study. Following a 3 week washout period, athletes were then exposed to the other condition. Athletes were tested for maximal oxygen consumption and time to exhaustion on an electromagnetically braked cycle ergometer before and after each treatment in addition to being tested for anaerobic performance (Wingate test) on a modified Monark cycle ergometer. Blood samples were taken throughout the experiment and vastus lateralis muscle biopsies were taken before and after each treatment. Increases in red blood cell count, haematocrit, haemoglobin, platelet number and erythropoietin concentration were observed following short-term normobaric hypoxia. Except for a modest decrease in phosphofructokinase activity following short-term normobaric hypoxia, no changes were observed in muscle enzyme activities, buffer capacity, capillary density or morphology. No performance measures were changed following short-term normobaric hypoxia or normobaric normoxia. Although short-term normobaric hypoxia exposure increased levels of a number of haematological parameters, this was not associated with improved aerobic or anaerobic performance in highly trained athletes.

Sleep disturbance at simulated altitude indicated by stratified respiratory disturbance index but not hypoxic ventilatory response

At high altitudes, the clinically defined respiratory disturbance index (RDI) and high hypoxic ventilatory response (HVR) have been associated with diminished sleep quality. Increased RDI has also been observed in some athletes sleeping at simulated moderate altitude. In this study, we investigated relationships between the HVR of 14 trained male endurance cyclists with variable RDI and sleep quality responses to simulated moderate altitude. Blood oxygen saturation (SpO2%), heart rate, RDI, arousal rate, awakenings, sleep efficiency, rapid eye movement (REM) sleep, non-REM sleep stages 1, 2 and slow wave sleep as percentages of total sleep time (%TST) were measured for two nights at normoxia of 600 m and one night at a simulated altitude of 2,650 m. HVR and RDI were not significantly correlated with sleep stage, arousal rate or awakening response to nocturnal simulated altitude. SpO2 was inversely correlated with total RDI (r = -0.69, P = 0.004) at simulated altitude and with the change in arousal rate from normoxia (r = -0.65, P = 0.02). REM sleep response to simulated altitude correlated with the change, relative to normoxia, in arousal (r = -0.63, P = 0.04) and heart rate (r = -0.61, P = 0.04). When stratified, those athletes at altitude with RDI >20 h(-1) (n = 4) and those with <10 h(-1) (n = 10) exhibited no difference in HVR but the former had larger falls in SpO2 (P = 0.05) and more arousals (P = 0.03). Neither RDI (without stratification) nor HVR were sufficiently sensitive to explain any deterioration in REM sleep or arousal increase. However, the stratified RDI provides a basis for determining potential sleep disturbance in athletes at simulated moderate altitude.

Does intermittent hypoxia increase erythropoiesis in professional cyclists during a 3-week race?

In this study we examined the effects of intermittent hypoxia exposure (IHE) in a group of professional cyclists (n = 6; age 26 +/- 1 yr) competing in the 2001 Vuelta a España. After each daily stage, treated subjects received four 5-min bouts of normobaric IHE (mean O2 concentration of 12.6%, simulating a mean altitude of 4,000 m) interspersed with 5-min bouts of breathing hotel room air (normoxia) until completing a total IHE of 20-min duration. The primary outcome, compared to a control group of similar characteristics not receiving IHE (n = 5; age 25 +/- 1 yr), was the % increase in erythropoietin (Epo) from the beginning to the end of the Vuelta. Statistical analysis showed that Epo increase tended to be higher (p = 0.052) in the IHE group than in controls (37.4 +/- 5.8% vs. -4.4 +/- 19.5%, respectively). However IHE had no effect on reticulocytes or erythrocyte count (p > 0.05).

Living high-training low altitude training: effects on mucosal immunity

Secretory immunoglobulin A (sIgA) is the major immunoglobulin of the mucosal immune system. Whereas the suppressive effect of heavy training on mucosal immunity is well documented, little is known regarding the influence of hypoxia exposure on sIgA during altitude training. This investigation examined the impact of an 18-day Living high-training low (LHTL) training camp on sIgA levels in 11 (six females and five males) elite cross-country skiers. Subjects from the control group (n=5) trained and lived at 1,200 m of altitude, whereas, subjects from the LHTL group (n=6) trained at 1,200 m, but lived at a simulated altitude of 2,500, 3,000 and 3,500 m (3x6-day, 11 h day(-1)) in hypoxic rooms. Saliva samples were collected before, after each 6-day phases and 2 weeks thereafter (POST). Salivary sIgA, protein and cortisol were measured. There was a downward trend in sIgA concentrations over the study, which reached significance in LHTL (P<0.01), but not in control (P=0.08). Salivary IgA concentrations were still lower baseline at POST (P<0.05). Protein concentration increased in LHTL (P<0.05) and was negatively correlated with sIgA concentration after the 3,000 and 3,500 m-phase and at POST (P<0.05 all). Cortisol concentrations were unchanged over the study and no relationship was found between cortisol and sIgA. In summary, data were strongly suggestive of a cumulative negative effect of physical exercise and hypoxia on sIgA levels during LHTL training. Two weeks of active recovery did not allow for proper sIgA recovery. The mechanism underlying this depression of sIgA could be mediated by neural factors.

Simulated hypergravity running increases skeletal and cardiovascular loads

PURPOSE

Eight recreational and eight competitive athletes were studied to determine the cardiovascular and musculoskeletal effects of running in hypergravity conditions simulated by the use of lower body negative pressure (LBNP). Subjects are sealed in a LBNP chamber with the use of a flexible, neoprene waist seal and the chamber pressure is reduced to provide an increased vertical force.

METHODS

Subjects ran on a treadmill at 1.0, 1.1, and 1.2 times body weight (BW) with increased loads provided by LBNP. Heart rate (HR), oxygen consumption (VO(2)), vertical ground reaction force (GRF), dynamic knee range of motion (ROM), and the electrical activities (EMG) of the tibialis anterior, medial gastrocnemius, vastus medialis obliquous, and biceps femoris muscles were measured.

RESULTS

LBNP produced a significant increase in HR at the 1.1-BW and 1.2-BW levels in both recreational and competitive athletes when compared with the 1.0 BW condition. Both VO(2) and GRF were increased significantly at 1.2 BW. No significant changes were observed in knee ROM or peak EMG amplitude with LBNP in either recreational or competitive athletes.

CONCLUSION

Increased HR and VO(2) indicate an increased cardiovascular load whereas increased GRF indicates an increased skeletal load. The lack of change in muscle activation and knee ROM point to a preservation in gait mechanics. Increased cardiovascular and skeletal loads with preservation of gait mechanics suggest that exercise within LBNP may be an effective training modality to improve athletic performance.

Factors affecting running economy in trained distance runners

Running economy (RE) is typically defined as the energy demand for a given velocity of submaximal running, and is determined by measuring the steady-state consumption of oxygen (VO2) and the respiratory exchange ratio. Taking body mass (BM) into consideration, runners with good RE use less energy and therefore less oxygen than runners with poor RE at the same velocity. There is a strong association between RE and distance running performance, with RE being a better predictor of performance than maximal oxygen uptake (VO2max) in elite runners who have a similar VO2max). RE is traditionally measured by running on a treadmill in standard laboratory conditions, and, although this is not the same as overground running, it gives a good indication of how economical a runner is and how RE changes over time. In order to determine whether changes in RE are real or not, careful standardisation of footwear, time of test and nutritional status are required to limit typical error of measurement. Under controlled conditions, RE is a stable test capable of detecting relatively small changes elicited by training or other interventions. When tracking RE between or within groups it is important to account for BM. As VO2 during submaximal exercise does not, in general, increase linearly with BM, reporting RE with respect to the 0.75 power of BM has been recommended. A number of physiological and biomechanical factors appear to influence RE in highly trained or elite runners. These include metabolic adaptations within the muscle such as increased mitochondria and oxidative enzymes, the ability of the muscles to store and release elastic energy by increasing the stiffness of the muscles, and more efficient mechanics leading to less energy wasted on braking forces and excessive vertical oscillation. Interventions to improve RE are constantly sought after by athletes, coaches and sport scientists. Two interventions that have received recent widespread attention are strength training and altitude training. Strength training allows the muscles to utilise more elastic energy and reduce the amount of energy wasted in braking forces. Altitude exposure enhances discrete metabolic aspects of skeletal muscle, which facilitate more efficient use of oxygen. The importance of RE to successful distance running is well established, and future research should focus on identifying methods to improve RE. Interventions that are easily incorporated into an athlete's training are desirable.

Effect of FIO2 on Oxidative Stress during Interval Training at Moderate Altitude

PURPOSE

To evaluate the effect of different fractions of inspired oxygen (FIO2) on oxidative stress during a high-intensity interval workout in trained endurance athletes residing at altitude.

METHODS

Subjects (N = 19) were trained male cyclists who were residents of moderate altitude (1800-1900 m). Testing was conducted at 1860 m (PB 610-612 torr, PIO2 approximately 128 torr). Subjects performed three randomized, single-blind trials consisting of a standardized interval workout (6 x 100 kJ) while inspiring a medical-grade gas with FIO2 0.21 (PIO2 approximately 128 torr), FIO2 0.26 (PIO2 approximately 159 torr), and FIO2 0.60 (PIO2 approximately 366 torr). Serum lipid hydroperoxides (LOOH) and whole-blood reduced glutathione (GSH) were measured 60 min preexercise and immediately postexercise, and analyzed using standard colorimetric assays. Urinary malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) were measured 24 h preexercise and 24 h postexercise, and analyzed via HPLC and ELISA, respectively.

RESULTS

Compared with the control trial (FIO2 0.21), total time (min:s) for the 100-kJ work interval was faster (5% in FIO2 0.26; 8% in FIO2 0.60 (P < 0.05)) and power output (W) was higher (5% in FIO2 0.26, 8% in FIO2 0.60 (P < 0.05)) in the supplemental oxygen trials. There was a significant pre- versus postexercise main effect (P < 0.05) for LOOH and GSH; however, there were no significant differences in LOOH or GSH between the FIO2 trials. MDA and 8-OHdG were unaffected by either the interval training session or FIO2.

CONCLUSION

Supplemental oxygen used in conjunction with high-intensity interval training at altitude ("live high + train low via supplemental O2" (LH + TLO2)) results in a significant improvement in exercise performance without inducing additional free radical oxidative stress as reflected in hematological and urinary biomarkers.

Vacation at moderate and low altitude improves perceived health in individuals with metabolic syndrome

BACKGROUND

Recent data suggest that vacation may improve cardiovascular health, an effect possibly moderated by altitude. The aim of the present study was to study the effect of a 3-week vacation at moderate and low altitude on perceived health in individuals with increased cardiovascular risk.

METHODS

Seventy-two overweight males, both occupationally active and retired (mean age=56.6 +/- 7.2 years), with signs of metabolic syndrome were randomly assigned to identical sojourns at either moderate (1,700 m) or low (300 m) altitude and engaged in four 3- to 4-h heart-rate-controlled hiking tours per week. Perceived health was measured 2 weeks before vacation, at the beginning and end of vacation, and 7 weeks after vacation.

RESULTS

Fitness, recreational ability, positive and negative mood and social activities improved during vacation, independent of altitude and occupational status, although the day-to-day improvement in quality of sleep was delayed at moderate altitude. During the follow-up examinations, improvements in all reported aspects of health except for social activities were maintained. In comparison to retired individuals, active individuals showed a greater long-term improvement in social activities.

CONCLUSION

Vacation positively affects perceived health independent of altitude or occupational status in generally inactive overweight males.

Sleep quality responses to atmospheric variation: case studies of two elite female cyclists

Strategies applied during sleep to potentially enhance athlete performance use different atmospheric conditions. High altitude conditions are known to affect sleep adversely but the effects of mild-moderate altitude and O2 enrichment at mild altitude are uncertain. We performed case studies using two elite female road cyclists (mass and maximal aerobic power of 62 kg, 65.8 ml x kg(-1) x min(-1); 57 kg, 62.7 ml x kg(-1) x min(-1)) to examine changes in sleep for different atmospheric conditions applied throughout the preparation for, and during, an International Stage race. Conditions were: i) normoxia (600 m), ii) simulated moderate altitude (2650 m), iii) natural mild altitude (1380 m) and iv) O2 enrichment at mild altitude (30% O2@ 1300-1500 m). We measured respiratory disturbances, arousals, number of awakenings, blood oxygen saturation (SpO2), heart rate (HR), rapid eye movement sleep (REM) and deep sleep. Respiratory disturbances, SpO2 and HR responses were similar for both cyclists for all conditions. Compared with normoxia, both cyclists had somewhat reduced REM at natural mild altitude and moderate simulated altitude but differed in their REM and deep sleep responses to O2 enrichment. Compared with mild altitude, both showed increased awakenings and deep sleep with O2 enrichment. Only one cyclist clearly increased her REM sleep with O2 enrichment compared to mild altitude. Our data highlight two different sleep quality responses to atmospheric variation.

Effect of intermittent hypoxia on oxygen uptake during submaximal exercise in endurance athletes

The purpose of the present study was to clarify the following: (1) whether steady state oxygen uptake (VO(2)) during exercise decreases after short-term intermittent hypoxia during a resting state in trained athletes and (2) whether the change in VO(2) during submaximal exercise is correlated to the change in endurance performance after intermittent hypoxia. Fifteen trained male endurance runners volunteered to participate in this study. Each subject was assigned to either a hypoxic group (n=8) or a control group (n=7). The hypoxic group spent 3 h per day for 14 consecutive days in normobaric hypoxia [12.3 (0.2)% inspired oxygen]. The maximal and submaximal exercise tests, a 3,000-m time trial, and resting hematology assessments at sea level were conducted before and after intermittent normobaric hypoxia. The athletes in both groups continued their normal training in normoxia throughout the experiment. VO(2) during submaximal exercise in the hypoxic group decreased significantly (P<0.05) following intermittent hypoxia. In the hypoxic group, the 3,000-m running time tended to improve (P=0.06) after intermittent hypoxia, but not in the control group. Neither peak VO(2) nor resting hematological parameters were changed in either group. There were significant (P<0.05) relationships between the change in the 3,000-m running time and the change in VO(2) during submaximal exercise after intermittent hypoxia. The results from the present study suggest that the enhanced running economy resulting from intermittent hypoxia could, in part, contribute to improved endurance performance in trained athletes.

Intermittent hypoxia improves endurance performance and submaximal exercise efficiency

The purpose of the present study was to elucidate the influence of intermittent hypobaric hypoxia at rest on endurance performance and cardiorespiratory and hematological adaptations in trained endurance athletes. Twelve trained male endurance runners were assigned to either a hypoxic group (n = 6) or a control group (n = 6). The subjects in the hypoxic group were exposed to a simulated altitude of 4500 m for 90 min, three times a week for 3 weeks. The measurements of 3000 m running time, running time to exhaustion, and cardiorespiratory parameters during maximal exercise test and resting hematological status were performed before (Pre) and after 3 weeks of intermittent hypoxic exposure (Post). These measurements were repeated after the cessation of intermittent hypoxia for 3 weeks (Re). In the control group, the same parameters were determined at Pre, Post, and Re for the subjects not exposed to intermittent hypoxia. The athletes in both groups continued their normal training together at sea level throughout the experiment. In the hypoxic group, the 3000 m running time and running time to exhaustion during maximal exercise test improved. Neither cardiorespiratory parameters to maximal exercise nor resting hematological parameters were changed in either group at Post, whereas oxygen uptake (.V(O2)) during submaximal exercise decreased significantly in the hypoxic group. After cessation of intermittent hypoxia for 3 weeks, the improved 3000 m running time and running time to exhaustion tended to decline, and the decreased .V(O2) during submaximal exercise returned to Pre level. These results suggest that intermittent hypoxia at rest could improve endurance performance and submaximal exercise efficiency at sea level in trained endurance athletes, but these improvements are not maintained after the cessation of intermittent hypoxia for 3 weeks.

Intermittent normobaric hypoxia does not alter performance or erythropoietic markers in highly trained distance runners

This study was designed to test the hypothesis that intermittent normobaric hypoxia at rest is a sufficient stimulus to elicit changes in physiological measures associated with improved performance in highly trained distance runners. Fourteen national-class distance runners completed a 4-wk regimen (5:5-min hypoxia-to-normoxia ratio for 70 min, 5 times/wk) of intermittent normobaric hypoxia (Hyp) or placebo control (Norm) at rest. The experimental group was exposed to a graded decline in fraction of inspired O2: 0.12 (week 1), 0.11 (week 2), and 0.10 (weeks 3 and 4). The placebo control group was exposed to the same temporal regimen but breathed fraction of inspired O2 of 0.209 for the entire 4 wk. Subjects were matched for training history, gender, and baseline measures of maximal O2 uptake and 3,000-m time-trial performance in a randomized, balanced, double-blind design. These parameters, along with submaximal treadmill performance (economy, heart rate, lactate, and ventilation), were measured in duplicate before, as well as 1 and 3 wk after, the intervention. Hematologic indexes, including serum concentrations of erythropoietin and soluble transferrin receptor and reticulocyte parameters (flow cytometry), were measured twice before the intervention, on days 1, 5, 10, and 19 of the intervention, and 10 and 25 days after the intervention. There were no significant differences in maximal O2 uptake, 3,000-m time-trial performance, erythropoietin, soluble transferrin receptor, or reticulocyte parameters between groups at any time. Four weeks of a 5:5-min normobaric hypoxia exposure at rest for 70 min, 5 days/wk, is not a sufficient stimulus to elicit improved performance or change the normal level of erythropoiesis in highly trained runners.

Drugs for increasing oxygen and their potential use in doping: a review

Blood oxygenation is a fundamental factor in optimising muscular activity. Enhancement of oxygen delivery to tissues is associated with a substantial improvement in athletic performance, particularly in endurance sports. Progress in medical research has led to the identification of new chemicals for the treatment of severe anaemia. Effective and promising molecules have been created and sometimes used for doping purposes. The aim of this review is to present methods, and drugs, known to be (or that might be) used by athletes to increase oxygen transport in an attempt to improve endurance capacity. These methods and drugs include: (i) blood transfusion; (ii) endogenous stimulation of red blood cell production at altitude, or using hypoxic rooms, erythropoietins (EPOs), EPO gene therapy or EPO mimetics; (iii) allosteric effectors of haemoglobin; and (iv) blood substitutes such as modified haemoglobin solutions and perfluorochemicals. Often, new chemicals are used before safety tests have been completed and athletes are taking great health risks. Such new chemicals have also created the need for new instrumental strategies in doping control laboratories, but not all of these chemicals are detectable. Further progress in analytical research is necessary.

Effect of F(I)O(2) on physiological responses and cycling performance at moderate altitude

PURPOSE

To evaluate physiological responses and exercise performance during a "live high-train low via supplemental oxygen" (LH + TLO(2)) interval workout in trained endurance athletes.

METHODS

Subjects (N = 19) were trained male cyclists who were permanent residents of moderate altitude (1800-1900 m). Testing was conducted at 1860 m (P(B) 610-612 Torr, P(I)O(2) approximately 128 Torr). Subjects completed three randomized, single-blind trials in which they performed a standardized interval workout while inspiring a medical-grade gas with F(I)O(2) 0.21 (P(I)O(2) approximately 128 Torr), F(I)O(2) 0.26 (P(I)O(2) approximately 159 Torr), and F(I)O(2) 0.60 (P(I)O(2) approximately 366 Torr). The standardized interval workout consisted of 6 x 100 kJ performed on a dynamically calibrated cycle ergometer at a self-selected workload and pedaling cadence with a work:recovery ratio of 1:1.5.

RESULTS

Compared with the control trial (21% O(2)), average total time (min:s) for the 100-kJ work interval was 5% and 8% (P < 0.05) faster in the 26% O(2) and 60% O(2) trials, respectively. Consistent with the improvements in total time were increments in power output (W) equivalent to 5% (26% O(2) trial) and 9% (60% O(2) trial; P < 0.05). Whole-body [VO](2) (L.min-1) was higher by 7% and 14% (P < 0.05) in the 26% O(2) and 60% O(2) trials, respectively, and was highly correlated to the improvement in power output (r = 0.85, P < 0.05). Arterial oxyhemoglobin saturation (S(p)O(2)) was significantly higher by 5% (26% O(2)) and 8% (60% O(2)) in the supplemental oxygen trials.

CONCLUSION

We concluded that a typical LH + TLO(2) training session results in significant increases in arterial oxyhemoglobin saturation, [V02] and average power output contributing to a significant improvement in exercise performance.

Effect of high-intensity hypoxic training on sea-level swimming performances

The objective of this study was to test the hypothesis that high-intensity hypoxic training improves sea-level performances more than equivalent training in normoxia. Sixteen well-trained collegiate and Masters swimmers (10 women, 6 men) completed a 5-wk training program, consisting of three high-intensity training sessions in a flume and supplemental low- or moderate-intensity sessions in a pool each week. Subjects were matched for gender, performance level, and training history, and they were assigned to either hypoxic [Hypo; inspired O2 fraction (Fi(O(2))) = 15.3%, equivalent to a simulated altitude of 2,500 m] or normoxic (Norm; Fi(O(2)) = 20.9%) interval training in a randomized, double-blind, placebo-controlled design. All pool training occurred under Norm conditions. The primary performance measures were 100- and 400-m freestyle time trials. Laboratory outcomes included maximal O(2) uptake (Vo(2 max)), anaerobic capacity (accumulated O(2) deficit), and swimming economy. Significant (P = 0.02 and <0.001 for 100- and 400-m trials, respectively) improvements were found in performance on both the 100- [Norm: -0.7 s (95% confidence limits: +0.2 to -1.7 s), -1.2%; Hypo: -0.8 s (95% confidence limits: -0.1 to -1.5 s), -1.1%] and 400-m freestyle [Norm: -3.6 s (-1.8 to -5.5 s), -1.2%; Hypo: -5.3 s (-2.3 to -8.3 s), -1.7%]. There was no significant difference between groups for either distance (ANOVA interaction, P = 0.91 and 0.36 for 100- and 400-m trials, respectively). Vo(2 max) was improved significantly (Norm: 0.16 +/- 0.23 l/min, 6.4 +/-8.1%; Hypo: 0.11 +/- 0.18 l/min, 4.2 +/- 7.0%). There was no significant difference between groups (P = 0.58). We conclude that 5 wk of high-intensity training in a flume improves sea-level swimming performances and Vo(2 max) in well-trained swimmers, with no additive effect of hypoxic training.

Intermittent hypoxia research in the former soviet union and the commonwealth of independent States: history and review of the concept and selected applications

This review aims to summarize the basic research in the field of intermittent hypoxia in the Soviet Union and the Commonwealth of Independent States (CIS) that scientists in other Western countries may not be familiar with, since Soviet scientists were essentially cut off from the global scientific community for about 60 years. In the 1930s the concept of repeated hypoxic training was developed and the following induction methods were utilized: repeated stays at high-mountain camps for several weeks, regular high altitude flights by plane, training in altitude chambers, and training by inhalation of low-oxygen-gas mixtures. To the present day, intermittent hypoxic training (IHT) has been used extensively for altitude preacclimatization; for the treatment of a variety of clinical disorders, including chronic lung diseases, bronchial asthma, hypertension, diabetes mellitus, Parkinson's disease, emotional disorders, and radiation toxicity, in prophylaxis of certain occupational diseases; and in sports. The basic mechanisms underlying the beneficial effects of IHT are mainly in three areas: regulation of respiration, free-radical production, and mitochondrial respiration. It was found that IHT induces increased ventilatory sensitivity to hypoxia, as well as other hypoxia-related physiological changes, such as increased hematopoiesis, alveolar ventilation and lung diffusion capacity, and alterations in the autonomic nervous system. Due to IHT, antioxidant defense mechanisms are stimulated, cellular membranes become more stable, Ca(2+) elimination from the cytoplasm is increased, and O(2) transport in tissues is improved. IHT induces changes within mitochondria, involving NAD-dependent metabolism, that increase the efficiency of oxygen utilization in ATP production. These effects are mediated partly by NO-dependent reactions. The marked individual variability both in animals and humans in the response to, and tolerance of, hypoxia is described. Studies from the Soviet Union and the CIS significantly contributed to the understanding of intermittent hypoxia and its possible beneficial effects and should stimulate further research in this direction in other countries.