A male Paralympic long-distance runner (1A = 30 y, 1.79 m, 64 kg) in the T11 class (visual acuity of less than LogMAR 2.60) and his two male guide runners (2G = 30 y, 1.74 m, 64 kg; 3G = 33 y, 1.84 m, 81 kg), who do not have any disabilities, underwent 30 days of altitude training in preparation for future competitions. The T11 class is designated for athletes who are totally blind or have a severe visual impairment. They must compete with a guide using a tether and are required to wear a blindfold or opaque glasses (23). The case athlete’s visual impairment is associated with a congenital retinal condition that was diagnosed in childhood and has progressively worsened over time, known as a congenital retinal disorder.

The chose for this case study based on the Paralympic athlete outstanding achievements in World championships and the Paralympic Games, as well as his thoroughly monitored training at real altitude. For example, this athlete is a Paralympic champion and World record holder in both the 1,500 m and 5,000 m events, having claimed the titles at the Tokyo 2020 + 1 Paralympic Games and the 2024 Kobe World Athletics Championships. He also won the world title in the 1,500 m in Paris 2023 and set the world record for the event at the 2024 Kobe World Championships. Recently, this athlete won a gold medal at the New Delhi 2025 World Para athletes Championship. Regarding his guides, although they are not officially recognized as record holders due to competitions regulations, their contribution is essential to the visually impaired athlete’s performance. To effectively accompany and support him during training and competition, the guides must possess exceptional physical, physiological, and running profile.

According to the anamnesis, the athlete and his two guides were professional athletes with completed secondary education. At the time of data collection, the athlete (1A) and one guide (3G) were enrolled in undergraduate programs. They had no food allergies or intolerances, did not use continuous medication, had no pathologies. They also did not present dental issues or problems interfering with food consumption, reported between 7 and 8 hours of sleep per day, did not have a smoking habit, and exhibited regular bowel habits. Nutritional monitoring was reported by only 1A and 2G, with 2G also reporting alcohol consumption twice a week, an aversion to vegetables, and a weight loss of 2 kilograms over the previous 2 months, corresponding to a 3.03% reduction in total body mass. 1A and 3G were married and lived with their spouses. They ate meals prepared by their wives at home. In contrast, 2G lived with another athlete and ate outside the home. Additionally, only 1A reported a family history of diseases such as hypertension, mentioning his mother.

Three athletes provided written consent, and the study was approved by the Research Ethics Committee of the Faculty of Medical Sciences, UNICAMP, Protocol No. CAAE 52313721.0.0000.5404.

The altitude training protocol was executed in Guarne city, Colombia, at approximately 2,150 m above sea level, with duration of 30 days. During this period, the athletes and technical team lived in the same residence, which facilitated control over nutrition, hydration, and recovery after training sessions. The program comprised weekly seven-day microcycles, encompassing a total of 11 training sessions. These sessions included two high-intensity interval training sessions, two strength training sessions in the gym, one plyometric session, one high-volume session, one flexibility session, and four regenerative sessions. The total weekly volume exhibited a range from 110 to 140 km. The athletes’ physiological acclimatization period and load progression were respected with adjustments in volume and intensity. The intensity of the training was individualized based on pre-altitude aerobic and anaerobic assessments, which allowed classification into three zones: zone 1 (Z1), considered low intensity, defined as a running pace below or at ventilatory threshold (vVT); zone 2 (Z2), defined as a pace between the vVT and respiratory compensation point velocity (vRCP) 2; and zone 3 (Z3), at or above the vRCP. These zones were used to guide the training periodization (8).

In the first week, the total training volume was 110 km, with 80 km performed at an intensity close to Z1, corresponding to the first ventilatory threshold (VT1), and 30 km in Z2, between VT1 and the respiratory compensation point (VT2). As part of the adaptation process to the effects of hypoxic exposure, both the training volume and intensity progressively increased over the following weeks. By the fourth week, the athletes completed 140 km of training, consisting of 90 km near Z1, 30 km within Z2, and 20 km in Z3. The athletes exhibited very similar physical conditioning, so the training sessions did not differ among them. The duration of the sessions, however, varied according to the training objective. Regenerative sessions at an easy pace lasted approximately 30 to 45 min, continuous endurance sessions ranged from 60 to 80 min, and interval sessions could last up to 120 min, including warm-up, main set, and cool-down. Strength training sessions lasted about 100 min, including warm-up. Strength training sessions were performed using free weights, with athletes completing three sets of 10 to 16 repetitions per exercise. The load was determined according to perceived exertion, aiming to reach near muscle failure in the final repetition of each set. Throughout the entire training period, all sessions were supervised by a coach specialized in Paralympic athletics.

Prior to departure for Colombia, the athlete and his guides underwent a comprehensive nutritional assessment and completed a food frequency questionnaire. The goal was to better characterize the sample, understand their socioeconomic profile, food preferences, and dietary habits. A 24-h Food Recall (24) was used to assess intake before and during the four-week training period, with data collected at five time points: one week before the program and weekly during training program. The recalls were conducted through direct interviews by the athletes’ personal coach, who had been previously trained by a sports nutritionist for this procedure and accompanied them throughout the entire training period. Given evidence that elite endurance athletes self-report consistent dietary practices across training cycles (25), weekly 24-h recalls were considered sufficient to capture representative dietary intake.

Basal metabolic rate (BMR) was estimated for each training participant using the Harris-Benedict equation (26). These values are presented as approximate estimates of individual energy expenditure. Total energy expenditure (TEE) was then calculated by applying a physical activity factor of 1.725 to the estimated BMR. Energy intake was assessed using 24-h dietary recalls and compared to the estimated TEE to determine whether training participants met the recommended requirements for high-performance athletes during the altitude training period. The data were analyzed by the sports nutritionist using Diet Box software version 8.1.6 to estimate energy expenditure and nutrient intake, and subsequently compared with recommendations for high-performance athletes.

Body mass was assessed at baseline using a Sanitas SBF 14 Max portable scale (100 g sensitivity), with measurements recorded three times per week. This parameter was collected in a standardized manner, with consistent timing and location (in the morning, with a maximum variation of 1 hour), and in a fasting state with minimal clothing.

The Lake Louise Symptom Score (LLSS) (12) was utilized to evaluate the presence of acute AMS, which is typified by the manifestation of headache, gastrointestinal discomfort (nausea), fatigue, and dizziness. Each symptom was evaluated on a scale ranging from 0 (absent) to 3 (severe/incapacitating). The total score was determined by summing the ratings for all four symptoms. The total score ranged from 3 to 5, indicating mild AMS; 6 to 9, moderate AMS; and 10 to 12, severe AMS. The presence of headache (a minimum of 1 point) was a mandatory criterion for AMS diagnosis. In order to circumvent the potential for confounding of travel-related symptoms, the LLSS was administered a minimum of 6 h after altitude exposure (12, 17). The LLSS was administered a total of eight times: six times at rest (on days 1, 2, and 3; and on the first day of weeks 2, 3, and 4), and twice post-exercise (4 h after training sessions at Zone 1 [low intensity, TZ1] and Zone 3 [severe intensity, TZ3]). These administrations were in accordance with the coach’s training protocol.

The evaluation of sleep was assessed using two validated instruments: the Pittsburgh Sleep Quality Index (PSQI) (27) and the Epworth Sleepiness Scale (ESS) (28). The PSQI comprises 19 self-reported items grouped into seven components, an additional five items optionally answered by a roommate, assessing sleep quality and disturbances over the past month. These questions are grouped into seven components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medications, and daytime dysfunction, generating a total score ranging from 0 to 21 points. A score between 0 and 4 indicates good sleep quality, scores between 5 and 10 indicate poor sleep quality, and scores above 10 represent the cutoff for sleep disorders (27). The ESS is a tool designed to evaluate the likelihood of dozing off in eight common daily situations, with a score ranging from 0 (no chance) to 3 (high chance). The total score ranges from 0 to 24, with values greater than 10 indicating excessive daytime sleepiness and values greater than 16 indicating severe sleepiness (28). Both questionnaires were self-administered at two distinct time points baselines (prior to altitude training) and post-altitude training (after 4 weeks of altitude exposure). The findings were then compared with established reference values from the literature to provide a context for interpretation (Figure 1).

Exposure to altitude can increase basal metabolic rate by 400 to 600 kcal/day, reduce appetite (32), decrease caloric intake, and increase fluid loss, all of which may contribute to weight loss (33). A review of the existing literature indicates that most studies attribute this to an inadequate energy balance (34). Therefore, increasing food intake in the early days of exposure may help prevent weight loss (35). In the present case report, athletes’ body mass remained stable, with intra-individual variation ranging from −2.74 to +1.50%. These findings are consistent with those reported in elite cyclists training for 21 days at moderate altitude, who showed changes between −1.34 and +0.99% in body mass (36). In the present study, meals were prepared daily by a professional chef under the supervision of a sports nutritionist to replicate the athletes’ cultural diets. This approach helped address common nutritional challenges faced when traveling with athletes, such as cultural and religious considerations, social preferences, special dietary needs, and food intolerances and/or allergies (37).

In the context of altitude expeditions, nutritional recommendations emphasize prioritizing carbohydrates as the main energy source, maintaining protein balance, and ensuring adequate hydration (34). Acute hypoxic exposure during steady-state aerobic exercise suppresses exogenous carbohydrate oxidation, suggesting that traditional guidelines may not fully meet early metabolic demands. However, this effect seems to normalize after acclimatization (38). Consuming carbohydrates 30 min before hypoxia appears beneficial, likely due to enhanced oxygen delivery, supported by increases in heart rate, ventilation, and oxygen saturation (39). Carbohydrate supplementation or increased intake of this macronutrient appears to be beneficial for maintaining or restoring glycogen stores and improving exercise tolerance (40), which can enhance performance in medium and long duration sports modalities or when athletes perform more than one training session per day. Moreover, adequate carbohydrate intake may help reduce peripheral fatigue, particularly during high intensity, short duration efforts such as the 100 m sprint in athletics. Therefore, meeting the athlete’s nutritional requirements, especially under hypoxic conditions, is crucial and seems to be associated with improved exercise tolerance, positively influencing physiological adaptations and overall performance (40).

Considering the ACSM recommendations for protein intake in athletes (1.2–2.2 g·kg⁻¹·day⁻¹) (29), it can be stated that, across all analyzed weeks, the athlete and his guides reported values within or above the recommended range. Evidence suggests that an intake of approximately 1. g·kg⁻¹·day⁻¹, may be beneficial for maintaining fat-free mass, particularly in situations of negative energy balance, as may occur under altitude conditions (41). In this context, although body composition was not assessed before and after altitude exposure, preventing confirmation of potential changes in lean mass, no major variations in body weight were observed. Furthermore, a high protein intake may increase satiety, potentially hindering the achievement of total energy requirements and leading to a reduction in carbohydrate intake, which could negatively affect glycogen levels (41). This hypothesis may help explain the findings observed in the present case study. Furthermore, athletes may follow restrictive diets, requiring attention to minimal lipid intake, which can negatively affect hormonal balance, absorption of fat-soluble vitamins, neural health, and muscle energy needs (31).

The present case study, applying the 2018 Lake Louise Acute Mountain Sickness Score (12), found symptoms such as headaches and fatigue during the first two days after arriving at moderate altitude. This finding emphasizes the need to reduce training intensity in the first days of exposure (8). A study of 38 individuals, 19 of whom were endurance-trained and 19 untrained, found symptoms of AMS in the first few days of exposure. The hypothesis proposed to explain the manifestation of symptoms during this period suggests that it may be attributable to an increase in resting metabolic rate and enhanced parasympathetic activity (42). A substantial degree of individual variability has been observed in the effects of exposure to altitude, and individuals may exhibit varying degrees of susceptibility to developing acute mountain sickness (AMS). In view of this, it has been posited that individuals exhibiting a diminished ventilatory response to hypoxia may be more susceptible to contracting this illness (43). For athletes exposed to altitude, monitoring for AMS should begin within 24 to 48 h after arrival, and interventions should be implemented according to the severity of the condition. In cases of mild AMS, as observed on D1 in the present study, training intensity should be reduced and recovery periods extended, as was applied in our protocol (44).

The decrease in oxygen partial pressure, combined with partial or total sleep deprivation and biological adjustments induced by altitude exposure, can negatively affect cognitive performance by impairing attention, decision-making, and mood, as well as increasing fatigue and reducing neuropsychological function (45, 46). A study conducted with 40 volunteers reported that 13 h of hypoxia reduced sleep efficiency and consequently impaired mood and reaction time after 28 h. Interestingly, these effects were reversed in participants who performed acute exercise at 50% of VO₂peak under hypoxia (46), with similar findings observed for moderate-intensity exercise in both normoxia and hypoxia (47). Pirlot et al. (48) also found that altitude training improved psychophysiological responses during early acclimatization at 2,800 meters. Considering that the present study followed a progressive acclimatization protocol, gradually increasing training intensity and volume while maintaining low-to-moderate intensities during the first week at altitude, this may explain the absence of significant changes in cognitive or sleep-related questionnaires between pre- and post-altitude assessments.

Research conducted with visually impaired individuals has demonstrated a higher prevalence of sleep disorders in this demographic compared to the general population (49, 50), indicating a heightened necessity for sleep monitoring in this population. In the present case report, only one of the guides exhibited poor sleep quality according to the Pittsburgh questionnaire. However, an investigation in Paralympic athletes in normoxia observed that excessive daytime sleepiness affected more than half of the sample (51). Pedlar et al. (52) propose that the acclimatization to hypoxia through the utilization of a normobaric hypoxia tent, in conjunction with an individualized assessment, could serve as a method for predicting the impact of these conditions on sleep quality and for identifying athletes who may be susceptible to poor sleep quality.

Furthermore, according to the literature, 50% of totally blind individuals without light perception present with non-24-h sleep–wake disorder, a condition uncommon in sighted individuals, characterized by alternating episodes of insomnia and daytime sleepiness interspersed with asymptomatic periods (53). This disorder leads to circadian misalignment, resulting in hormonal dysregulation and potentially causing mood disturbances, loss of appetite, and gastrointestinal issues. Therefore, investigating sleep disorders in blind individuals becomes essential (54), as exemplified by the athlete in this case study.

In a study of 479 athletes, 52% scored ≥5 on the PSQI, raising questions about the suitability of this instrument for assessing sleep quality in athletic populations, as it may overestimate sleep problems (55). In the present case study, only one guide scored 5, which may reflect factors suggested in previous research, including caffeine intake (56), training schedules, sport-related stress and anxiety, social media use, and other lifestyle or environmental influences (55). Furthermore, 28% of athletes in a sample of 175 exhibited ESS scores ≥10, indicating substantial daytime sleepiness (57), consistent with the athlete (ESS = 13) and one guide (ESS = 10) in this study. Considering this, it may be valuable to provide athletes with guidance aimed at optimizing total sleep duration, sleep timing, and sleep quality. Strategies could include incorporating naps and extended nocturnal sleep, practicing sleep hygiene, engaging in mindfulness, and limiting the use of electronic devices before bedtime, all of which have been suggested to enhance both physical and cognitive performance (58).

Although the case study has advanced knowledge in research on elite athletes, including a Paralympic, by integrating different approaches to investigate the physical training at altitude, some limitations can be considered.

First, it is important to acknowledge that the equations used to estimate basal metabolic rate and total energy expenditure provide only approximate values, which may fluctuate according to variations in training intensity and duration over time. The influence of these factors under hypoxic conditions remains uncertain, and no laboratory assessments or additional objective measurements beyond body mass were conducted. Future investigations should address this limitation by employing indirect calorimetry or other objective techniques. Another limitation concerns the potential underreporting associated with self-reported questionnaires, which rely on the honesty and memory of participants and can be influenced by contextual and social factors. Understanding individual characteristics is essential to ensure data reliability (59). Nevertheless, it is worth noting that questionnaires can be easily implemented by coaches and serve as valuable complementary tools for monitoring variables that may affect training outcomes. Furthermore, ventilatory and hematological parameters were not evaluated, which could have provided deeper insight into individual physiological responses to altitude exposure. Future studies should incorporate these assessments to better elucidate interindividual variability and adaptation mechanisms associating with nutritional and sleep quality.

Finally, it is crucial to emphasize the need for additional research to develop evidence-based nutritional and sleep recommendations for training in hypoxic environments, including in Paralympic context. Expanding the sample size would enhance data reproducibility and generalizability, enabling robust statistical analyses. However, this case study centers on a Paralympic world record holder and his guide, whose exceptional achievements offer unique insights into elite athletic performance. These findings also highlight critical knowledge gaps that must be addressed to ensure the effective and safe implementation of altitude training protocols.