Abstract
High-altitude environments present unique physiological challenges for athletes, particularly in endurance sports. This review synthesizes the current literature on acute and chronic adaptations to hypobaric hypoxia, which collectively influence aerobic exercise performance during competitions at very high altitude. The benefits of acclimatization for improving endurance performance are offset by risks, including altitude sickness, sleep disorders, and muscle loss, if the acclimatization strategy is not properly planned. We evaluate different strategies, highlighting their efficacy in optimizing performance while mitigating drawbacks. Nutritional interventions and psychological techniques can also affect the maintenance of physical performance at high altitudes. Despite individual variability in adaptation, gradual ascent and pre-acclimatization emerge as best practices for minimizing health risks and performance loss. The review highlights the need for tailored preparation protocols, particularly for competitions at very high altitudes, and identifies gaps in knowledge regarding preparation strategies and health effects. By integrating insights from physiology, nutrition, and psychology, this review aims to offer recommendations to help athletes and coaches navigate the complexities of adequate preparation for high-altitude sports competitions.
Introduction
High and very high altitudes, defined as altitudes 2500 to 5800 meters, pose distinct physiological challenges for athletes. 1 Moderate altitude, in contrast, is defined as altitudes between 1500 and 2500 meters, with less demand on athletes. 2 The reduced atmospheric pressure at high elevations results in a lower availability of breathable oxygen, triggering a series of acute and chronic adaptations in the human body. 3 These adaptations can have considerable implications for athletes’ performance, especially in endurance sports performed at high and very high altitudes.4,5 However, the benefits of acclimatization for improving endurance performance can be offset by risks, including altitude sickness, sleep disorders, and muscle loss, if the acclimatization strategy is not properly planned. High-altitude training is increasingly accepted as an elite strategy to gain a competitive advantage by improving aerobic capacity and overall endurance in athletes competing at low to moderate altitudes.6,7 The drawbacks include altitude sickness, reduced training intensity, and individual variability in adaptation. 8
This review aims to evaluate the effectiveness of various acclimatization and high-altitude training strategies for enhancing athletic performance at high and very high altitudes. It also considers potential health-related issues, such as altitude illnesses. Furthermore, by integrating insights from physiology, nutrition, and psychology, this review aims to offer recommendations to help athletes and coaches navigate the complexities of effective preparation for high-altitude sports.
Methods
For this review, athletes have been defined as individuals who participate in organized sports that require systematic or regular physical training and compete regularly against one another.9,10 Athletes can be classified as elite, competitive, or recreational based on their training and competition objectives and the time dedicated to preparing for competitions. 11 From these definitions we can infer high altitude athletes as the athletes competing in activities or sports that involves spending time at high altitude as a part of the competition, which includes but is not limited to high altitude trail/endurance/sky running (e.g., Yading Skyrun with highest point at 4700 m, Khardung la Challenge reaching 5359 m, Ladakh marathon happening between 3000 m and 5370 m, Everest Marathon that starts at 5350 m and ending at 3400 m, etc.), long distance bike races (e.g., Yak Attack Nepal going upto 5416 m, Leadville trail 100 MTB going upto 3840 m) or mountaineering activities.
A structured literature search across major electronic databases was conducted using specific keywords and MeSH terms. The search method used keywords, their combinations, and relevant prepositions and conjunctions. The search terms included “high-altitude”, “altitude”, “athlete”, “acclimatization”, “hypoxia”, and “training”. The search focused on literature published between 1995 and 2025. Studies were included if they met the following criteria: 1. Peer-reviewed scientific articles, 2. published in English, and 3. focused on altitude/hypoxia training strategies to improve competition outcomes for athletes competing at high and very high altitudes, along with psychological training strategies for athletes in general. We excluded animal studies and studies not published in English. We initially identified 2380 papers. After applying the inclusion and exclusion criteria, we reviewed 113 papers in detail to synthesize this paper. The extracted data were then thematically synthesized to provide a coherent overview of the current understanding, highlighting key findings and identifying areas for future research.
High-altitude adaptation and adverse conditions
High-altitude exposure puts significant stress on the human body due to reduced atmospheric pressure and lower oxygen availability. It triggers respiratory, cardiovascular, neurologic, metabolic, and musculoskeletal adaptations aimed at restoring the body to its pre-exposure physiological homeostasis.12–14 For athletes, these conditions trigger acute and chronic physiological changes that can affect performance at high and very high altitudes and may also affect athletes’ health.
Immediately after exposure to high altitude, resting and sub-maximal heart rate and cardiac output increase to compensate for reduced arterial oxygen levels.3,14 However, prolonged exposure to high altitudes can reduce cardiac output driven by reduced stroke volume and increased oxygen content (hemoconcentration and increased red blood cell mass).15,16
In addition to cardiovascular changes, hypobaric hypoxia at high altitudes increases minute ventilation.17,18 This, in turn, leads to a decrease in arterial carbon dioxide, which causes respiratory alkalosis. Hypoxia also triggers pulmonary vasoconstriction. 19 These changes are more marked during exercise due to increased oxygen demand. 20 The reduction in air density with increasing altitude also decreases airway resistance, thereby improving respiratory airflow and forced exhalation.21,22 High-altitude environments are generally cooler and drier, which can trigger bronchospasms and exacerbate asthma during training or competition. 21 However, the low prevalence of allergens in these environments can also reduce the risk of allergen-triggered asthma exacerbations. 17
Immediately after arriving at high altitude, plasma volume constricts to increase oxygen content and improve oxygen delivery.14,23 Hypoxia also increases the stability of hypoxia-inducible factors (HIF), 24 leading to the activation of many genes, including those encoding erythropoietin. 25 This increases erythrocyte production,14,26,27 and the subsequent increase in red blood cells is the primary mechanism proposed to improve endurance capacity in athletes upon returning to sea level. 28 However, when exercising at very high altitudes, these increases seem not to confer benefits, as even blood transfusion did not improve exercise performance above 4000 m.29,30
In addition, athletes may exhibit increased capillary density in skeletal muscles, enabling more effective oxygen extraction and utilization at the tissue level.31,32 Another significant change is the upregulation of mitochondrial enzymes, which increases the muscles’ aerobic energy production, even under hypoxic conditions.33,34
Although the acclimatization process can partially compensate for reduced oxygen levels at high altitude, some losses in exercise performance relative to sea level will remain. 35 Moreover, high-altitude travel and stays can pose some health risks. 36 This is mainly the case when exposure duration extends over several hours and days. Altitude sickness, including acute mountain sickness (AMS), high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema (HACE), can occur in some individuals, particularly during rapid ascents without proper acclimatization.37,38 These illnesses can severely impair one's ability to train or compete and, in the case of HAPE and HACE, can even be life-threatening. 1
Preparing for competitions at high altitudes and possible negative influencing factors
High-altitude acclimatization represents a powerful tool for enhancing athletic performance at altitude, particularly in endurance sports, by leveraging the physiological adaptations triggered by hypoxic environments. Very few studies have examined how to optimize training strategies for high-altitude activities and sports, including mountaineering and high-altitude trail races.
In addition to appropriate altitude acclimatization strategies, health, nutritional, and psychological factors must also be considered to optimize athletic performance at altitude. All these factors are discussed in the following sections.
Altitude acclimatization strategies
Continuous altitude exposure for the improvement of performance at high altitude
Acclimatization to high altitude significantly impacts exercise performance at altitude, with key adaptations occurring within the first two weeks. Upon initial exposure to high altitude, athletes experience a marked decrease in performance due to reduced arterial oxygen content. However, as mentioned before, compensatory physiological changes, such as hyperventilation and hemoconcentration (an increase in hematocrit due to plasma volume loss), gradually improve oxygen delivery. 4
While VO2max remains significantly depressed upon initial ascent and shows only marginal recovery over time, submaximal endurance capacity, the primary determinant for long-distance performance, improves substantially with acclimatization. Studies demonstrate that time to exhaustion at a fixed submaximal workload can increase by 31% to 59% within the first two weeks of exposure.39,40 This endurance enhancement typically plateaus after 14 days, suggesting that at least 2 weeks is necessary to optimize performance prior to competition.39–41 When such extended periods are not feasible, even brief interventions, such as spending two nights at a moderate altitude of 3200 m, have been shown to partially restore aerobic and anaerobic exercise capacity. 42 Additionally, “staging” at intermediate altitudes (e.g., 6 days at 2200 m) before ascent to 4300 m has been shown to reduce the severity of acute mountain sickness and may slightly induce ventilatory acclimatization, which may help maintain functional performance at higher elevations. 43
Exposure beyond three weeks may yield additional performance benefits due to factors such as erythropoiesis; however, these effects vary and are not consistently observed across individuals, particularly among well-trained athletes.44–46
Intermittent altitude exposure for the improvement of performance at altitude
Short-term Intermittent Hypoxic Exposure (IHE), typically involving 1–4 h of daily exposure for one week, induces ventilatory acclimatization but yields inconsistent results regarding exercise performance at altitude. Although normobaric and hypobaric hypoxia can produce similar reductions in inspired oxygen availability, evidence suggests they are not physiologically equivalent, with hypobaric hypoxia generally producing greater ventilatory stress and altitude-related symptom burden.47,48 Research indicates that brief daily normobaric hypoxia exposure of 1–2 h is insufficient to enhance endurance performance in well-trained athletes during subsequent altitude sojourns.49,50 In contrast, a more substantial dose of 4 h of hypobaric hypoxia per day over seven consecutive days has been shown to significantly improve time-trial performance and increase arterial oxygen saturation at 4300 m. 51 This suggests that a threshold of daily exposure duration may be necessary for IHE to confer a functional competitive advantage. Furthermore, structured IHT protocol utilizing normobaric hypoxic environments for high-intensity sessions (2–3 times per week for 4–6 weeks) at simulated altitudes of 2500 m and 3000 m has demonstrated clear performance benefits. Studies indicate that while training in these normobaric conditions significantly enhances submaximal endurance and power output at altitude, the resulting impact on VO2max appears specific to hypoxic testing rather than translating to sea-level performance.52,53 Specifically, these normobaric protocols have been shown to improve time to exhaustion and cycling efficiency at moderate altitude, suggesting that localized muscular or metabolic adaptations occur even without the reduced barometric pressure found in natural high-altitude settings.52,53 To stimulate erythropoesis, longer daily hypoxic exposure times over several weeks, with models like live high train low (LHTL) are required. Athletes must achieve a cumulative hypoxic dose of at least 300 to 400 h at altitudes between 2000 m and 3000 m to see a statistically significant increase in red cell mass. 54 Most supporting data derive from LHTL studies performed in both hypobaric hypoxia and normobaric hypoxia, even though the hypoxic stimulus might be higher in hypobaric hypoxia, erythropoietic responses may be similar if adequate doses of normobaric hypoxia are applied. The importance of this threshold is evident in comparative studies: elite swimmers who underwent 13 days of normobaric LHTH (living at 2500 m for 11 h/day, totalling 150 h) showed no change in hemoglobin mass or aerobic performance. 55 In contrast, elite runners who extended the normobaric hypoxia protocol to 18 days (living at 2500–3000 m for 14 h/day, totaling 250–300 h) achieved a 5% increase in hemoglobin mass and a significant increase in VO2max. 56 This suggests that while 12–14 h per day is a functional minimum, the total duration of the sojourn must extend beyond the 18 days to consistently elicit systematic hematological benefits. Important to note that, for hematological adaptation, the human body needs adequate iron levels and storage before exposure to high altitude and/or hypoxia.57,58 Monitoring of iron profile is essential as insufficient stores can blunt the erythropoietic response to hypoxia. Stellingwarf et al. recommended achieving an optimal serum ferritin level of >100 ng/ml and transferrin saturation of >20% before departure. 59 These targets are significantly higher than the general clinical normal of >30 ng/ml, to ensure adequate iron bioavailability during the stress of altitude. Sex-related differences are a key factor as female athletes face a higher risk of deficiency due to menstrual loss and elevated hepcidin levels, which further inhibit iron absorption during the inflammatory response to hypoxia. 59 The effect of increased red blood cell mass on exercise performance at high altitude, however, appears limited, as neither erythropoietin administration 60 nor blood transfusion improved performance above 4000 m.29,30
Beyond hematological shifts, prolonged intermittent hypoxic exposure, specifically through the normobaric LHTL model, induces significant non-hematological adaptations in metabolic efficiency, muscular buffering, and ventilatory drive. Research indicates that living at simulated altitudes of 2500 m to 3000 m for 8 to 11 h per day over a period of 20 to 23 days 9totaling 160–250 h) can improve running economy by approximately 3% and enhance cycling efficiency.61–63 These improvements in energy economy are often observed without a corresponding increase in hemoglobin mass, suggesting that the stimulus of normobaric hypoxia triggers peripheral adaptations such as increased mitochondrial efficiency or glucose transport.62,64 Furthermore, similar LHTL protocols (living at 3000 m for 9 to 11 h/day for 20 + days) have been shown to increase muscle buffering capacity by up to 18%, allowing athletes to better manage metabolic acidosis during high-intensity efforts.63,64 Additionally, these specific exposure parameters (20 days at 2650 m for 9 to 11 h/day) significantly increased the hypoxic ventilatory response in well-trained endurance athletes, which may contribute to improved ventilatory acclimatization and potentially better maintenance of arterial oxygen saturation during subsequent exercise at altitude. 65 To achieve this effect, athletes can use intermittent hypoxia during exercise, which appears more beneficial than intermittent hypoxia exposure at rest. The intensity of hypoxic exercise influences molecular adaptations in skeletal muscle by activating the HIF gene. 66 There is also evidence that intense exercise at high altitudes stimulates muscle adaptations for both aerobic and anaerobic exercise and limits the decrease in power at sea level.67,68
As the landscape of altitude training evolves, a more integrated approach known as “Living high, Training Low and High” (LHTLH) has emerged as a potent strategy for peak performance. This model seeks to synergize the hematological benefits of chronic altitude exposure (erythropoiesis) with peripheral, non-hematological adaptations triggered by hypoxic exercise, such as improved mitochondrial efficiency and muscle buffering capacity.69,70 By sleeping at moderate altitudes of around 2500 m (hypobaric hypoxia), while alternating between high intensity training at or near sea level and specific interval sessions performed in simulated normobaric hypoxia equivalent to approximately 3000 m, athletes may achieve a dual-adaptation stimulus. 69 However, the cumulative internal load of the LHTLH model is significant. Recent longitudinal data in elite athletes indicates a decrease in heart rate variability and increased sleep fragmentation during the first term, which is the first 7 days, and the second term, which is 7 to 14 days of the acclimatization phases.71,72 While these autonomic and psychological markers, including perceived fatigue and mood tension, tend to stabilize after the second week, the protocol requires diligent monitoring to prevent overreaching. 72 Despite these recovery challenges, the LHTLH framework has demonstrated clinical and field efficacy, notably serving as a foundational acclimatization strategy for the fastest known time records on Mount Everest, where it was used to pre-acclimatize athletes for extreme altitudes while maintaining high-intensity mechanical power. 70
Nutritional aspects for high altitude performance
At altitudes exceeding 4300 m, acute and chronic exposure triggers a metabolic shift characterized by a decreased reliance on lipid oxidation and a corresponding increase in blood glucose dependence during both exercise and rest.73,74 This systemic preference for carbohydrate utilization, even at the cellular level within permeabilized muscle fibers, necessitates higher carbohydrate intake to replenish glycogen stores and prevent hypoglycemia.59,75,76 For athletes at these elevations, maintaining blood glucose is a performance and immunological priority, as exercise-induced hypoglycemia at altitude is linked to increased pro-inflammatory immune activation. 77 Furthermore, the physiological stress of high-altitude hypoxia actively promotes skeletal muscle catabolism. While modest weight loss can occur at moderate elevations, a systematic meta-analysis indicates that significant reductions in fat-free mass become more pronounced above 4000 m to 5000 m due to an inflammatory and oxidative state that impairs mitochondrial function and stimulates muscle tissue mobilization.78,79 This altitude-induced sarcopenia is driven by inhibited protein synthesis and increased proteolysis, which can severely compromise athletic power. 80 To mitigate this, athletes may benefit from low-volume, high-density protein supplementation, specifically focusing on branched-chain amino acids like leucine. Protocols involving leucine-rich supplementation during high-altitude treks (to 5300 m) have been shown to improve muscle protein synthesis and assist in retention of lean body mass despite the catabolic environment.81,82
During the initial 3–5 days of high-altitude exposure, typically more than 3000 m, athletes face a significant risk of dehydration driven by a three-fold increase in respiratory loss of water from hyperpnea in cold, dry air, and an obligatory high altitude diuresis as the body attempts to concentrate hemoglobin.83,84 Furthermore, a 15–20% increase in basal metabolic rate at extreme altitudes further accelerates insensible fluid loss.83,85 To maintain euhydration, it is recommended that athletes increase daily fluid intake by an additional 1 to 1.5 liters above sea level requirements, aiming for a total intake of 4 to 5 liters per day, depending on exercise intensity and environmental conditions.83,86 Hydration status should be monitored daily using a triad of indicators: mody mass stability (aiming for <1% fluctuation), urine specific gravity (<1.020), and subjective thirst, as thirst cues alone are not often blunted by hypoxia.87,88 Maintaining adequate hydration is critical not only for performance but also for reducing the severity of acute mountain sickness symptoms, which can be exacerbated by hypovolemia.83,88
Hypoxic conditions also impair antioxidant status and remain impaired for 2 weeks after altitude training. 89 While antioxidant supplements may not reduce oxidative stress, consuming more antioxidant-rich foods has been reported to be safe, not to hinder altitude adaptation, and may increase hemoglobin levels.89,90 Probiotic supplementation at least 2 weeks before altitude training or competition may reduce the risk of respiratory and gastrointestinal illness. 91 Although RCTs regarding the effects of vitamin D supplementation on mood and sleep are lacking, there are some observational studies that have shown some positive impact. Vitamin D plays a role in enhancing erythropoiesis by suppressing hepcidin, thereby increasing iron bioavailability for hemoglobin synthesis.92,93 Athletes with insufficient status should aim for maintenance or corrective dosages (2000 to 4000 IU/day) to support both hematological health and serotonergic pathways to regulate mood and sleep architecture.92,94 Sleep quality, often compromised at altitude, can be supported through the tryptophan-serotonin-melatonin axis. Dietary intake of L-tryptophan (1 gm taken 30–60 min before bedtime) has been shown to reduce sleep latency and improve sleep efficiency in elite athletes.95,96 This process is further enhanced by high-glycemic carbohydrate consumption, which stimulates insulin-mediated uptake of large neutral amino acids into skeletal muscle. This reduces competition at the blood-brain barrier and increases tryptophan to large neural amino acid ratio, allowing more tryptophan to enter the brain for serotonin production.97,98 Additionally, antioxidant-rich foods and foods containing natural melatonin (e.g., tart cherry juice) can mitigate hypoxia-induced oxidative stress and further improve sleep duration and recovery.95,99
To optimize performance and minimize the risk of altitude-induced illness, a high-altitude diet plan must be structured into two distinct phases: a pre-expedition loading phase and an active altitude-maintenance phase. During the 4–6 week preparation period, the primary focus is on maximizing iron stores to support erythropoiesis; athletes should aim for a serum ferritin>100 ng/mL through iron-rich foods and targeted supplementation,58,59 while also ensuring vitamin D levels are sufficient to regulate the iron-regulatory hormone hepcidin.92,100 Once at the altitude of more than 3000 m, the plan shifts to a high-carbohydrate, energy-dense strategy, as the body's metabolic crossover increases glucose dependence and suppresses fat oxidation.73,74 Athletes should aim for a carbohydrate intake of 7–10 gm/kg/day to preserve muscle glycogen and prevent hypoglycemia-induced immune stress.59,77 To counteract the common loss of fat-free mass seen in hypoxic environments, the protein intake should be maintained at 1.6–2.2 gm/kg/day,79,81 with a specific emphasis on leucine-rich sources (>3gm per meal) to stimulate muscle protein synthesis.80,82 Finally, a strict hydration protocol, adding 1–1.5 liters per day of electrolyte-enriched fluids above sea-level baseline, is essential to offset the massive increase in respiratory water loss and high-altitude diuresis.83,84
Altitude-related illnesses
Travel to high altitudes exposes one to hypobaric hypoxia, which leads to physiological stress and acclimatization. If acclimatization is inadequate for the altitude attained, it can lead to altitude-related illnesses. 101 This includes AMS, HACE, and HAPE.1,102 Athletes engaged in rapid ascent and prolonged stay (i.e., of several hours), such as ultra-trail runners or rapid climbers, are at higher risk of developing these illnesses, which can interfere with performance and be fatal. 103 These illnesses can be prevented by following a slow-ascent profile, as outlined in detail by Luks et al. 101 Other less common illnesses can also affect the activities or performance at high altitude, including but not limited to altitude-related cough, 104 high altitude retinopathy,105,106 and neurologic conditions other than AMS and HACE, for instance, high altitude psychosis. 105
Sleep at high altitude
High-altitude athletes frequently experience fragmented sleep characterized by poor quality and repetitive awakenings.107,108 These disturbances are primarily driven by altitude-induced changes in acid-base balance and heightened central chemosensitivity, resulting in periodic breathing, a cyclical ventilatory pattern alternating between hyperpnea and central sleep apnea. 109 While periodic breathing is a hallmark of sleep at elevations above 2000 m and nearly universal above 5000 m, its severity depends on an individual's hypoxic ventilatory response. 110 While periodic breathing increases respiratory effort, recent evidence suggests it may not significantly alter mean nocturnal oxygen saturation in healthy young males compared to steady breathing. 111 However, the resulting sleep fragmentation, marked by frequent arousals and reduced sleep, significantly impairs recovery and daytime cognitive function. 112
Beyond sleep, periodic breathing persists into wakefulness and manifests in approximately 25% of healthy individuals during incremental exercise in hypoxic conditions.113,114 This exercise-induced periodic breathing, driven by unstable ventilatory feedback loops, causes pronounced cyclic drops in arterial oxygen saturation and increased autonomic stress, evidenced by fluctuations in heart rate variability.113,115 Such oscillations reduce ventilatory efficiency and correlate with a decline in maximal aerobic power, ultimately accelerating fatigue and hindering athletic performance at extreme altitudes.113,114
Psychological aspects at high altitude
Psychological factors play a vital role in athletes’ performance. 116 Evidence regarding the psychological elements of high-altitude competitions has rarely been studied. 4 However, there are studies done on endurance athletes at moderate altitude (1500–2500 m), without exposure to high altitude, from which we will attempt to derive some recommendations. Altitude can negatively affect several aspects of cognitive function, motor speed/precision, complex reaction time, decision-making, and cerebral function. The effects become more pronounced with increasing altitude.117,118 Exhaustion during the activity can amplify the impact on cognitive functions. 119 Decision-making can be impaired with increased risky behavior at simulated altitude.120,121 Decision-making is essential to pacing during endurance activity. 122 This impaired decision-making can lead to overpacing and endanger athletes’ lives on challenging terrain. The peak in this impairment occurs after the initial few hours of exposure to hypoxia, and it slowly gets better with time in a hypoxic environment. 123 Athletes’ mood state can also affect their performance. 124 Performance is associated with a certain level of arousal state or anxiety. Very high or very low levels of anxiety can negatively affect performance. 125 An increase in the level of anxiety has been reported with increasing altitude. 126 Perception of a higher level of fatigue during the activity negatively affects the performance. Evidence indicates that carbohydrate supplementation can reduce perceived effort and improve performance at altitude. 127 So, carbohydrate supplementation before an activity or competition can be hypothesized to have positive psychological effects.
Athletes at high altitude can also employ several psychological strategies that have been shown to enhance endurance performance. These strategies include association, dissociation, imagery training, self-talk, and goal setting.116,128,129 Association is a strategy in which athletes identify the body signals of pain, fatigue, and muscle soreness and adjust their pace accordingly. Dissociation is a technique in which athletes attempt to distract themselves from these negative signals. This can be achieved by listening to distracting music, a podcast, or by engaging in a mental exercise, such as constructing something in mind or doing mathematics. Both techniques increase endurance performance. 116 Association appears more beneficial for elite athletes, whereas dissociation appears more effective for non-elite athletes. 130 The imagery technique involves simulating specific scenarios before the competition or activity. Self-talk interventions include talking to oneself and encouraging oneself before or during the activity. Goal setting before the activity also enhances endurance performance.
Summary and recommendations
High-altitude environments present unique physiological challenges for athletes. Reduced oxygen availability at altitude triggers acute responses (elevated heart rate, hyperventilation) and chronic adaptations (elevated erythropoietin, enhanced capillary density, and increased mitochondrial efficiency) to improve oxygen delivery and utilization. These adaptations can limit some of the endurance performance loss at altitude, but maladaptation to high altitude also carries potential risks. Risks include altitude sickness, sleep disturbance, and muscle loss due to increased catabolism.
Practical recommendations that could be derived from these considerations regarding high-altitude competitions or activities:
Gradual ascent to the altitude as per Wilderness Medical Society clinical practice for proper acclimatization to prevent altitude-related illnesses. This also helps with sleep management. Early arrival at the altitude is necessary to familiarize oneself with the environment and to avoid riskier decision-making. For optimal performance at high altitude, at least 2 weeks of acclimatization are needed before competing. This also helps with mood and sleep. If early arrival at the competition altitude is not feasible, pre-acclimatization to the same altitude in simulated altitude may be beneficial. Supplementation with high-carbohydrate snacks at altitude, where appetite suppression is common, seems beneficial. Additionally, increased carbohydrate intake before and during the activities might be recommended. In cases of iron deficiency, increased iron intake by incorporating iron-rich foods is recommended. Adding iron absorption enhancers such as vitamin C, and avoiding inhibitors such as coffee, tea, and calcium may also be foreseen. Adequate hydration management during the early days of high-altitude travel, when insensible water loss is high, is advisable. After the activity, athletes may consume high-quality protein stimulate protein synthesis and prevent muscle loss. Supplements containing leucine might help reduce muscle wasting. A small amount of tryptophan supplementation at high altitude may improve mood and sleep quality. An adequate intake of antioxidant-rich foods should be considered safe. Probiotic supplementation may help prevent respiratory and gastrointestinal illnesses during travel and activity. Vitamin D supplementation may help with iron utilization and improve mood and sleep.
The effects of high altitude on athletes’ physiology are multifaceted. It entails both benefits and potential disadvantages. Knowledge of these effects is essential for optimizing training programs and improving athletes’ performance at high altitudes. Future research should focus on optimizing protocols for sports competitions performed at very high altitude (e.g., ultra-trail runs, high-altitude mountain bike races, and mountaineering). Individualized training is a powerful tool for endurance athletes but requires meticulous planning to harness physiological adaptations without compromising health or performance. From this perspective, the previous recommendations must be evaluated on an individual basis to maximize the benefits.
Footnotes
Author contributions
SSB conceptualized the study and wrote the original draft; HG conceptualized the study and reviewed and edited the draft. All authors have read and approved the final version of the manuscript and agree with the order of presentation of the authors.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Declaration of generative AI and AI-assisted technologies in the writing process
During the preparation of this work, the authors used Grammarly to improve the grammar and sentence structure. After using the tool, the authors reviewed and edited the content as needed and assumed full responsibility for the publication.