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Altitude classifications.

Altitude classifications.

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Abstract Endurance athletic performance is highly related to a number of factors that can be altered through altitude and hypoxic training including increases in erythrocyte volume, maximal aerobic exercise capacity, capillary density, and economy. Physiological adaptations in response to acute and chronic exposure to hypoxic environments are well...

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... altitude increases, atmospheric pressure decreases, and although the fractional concentration of oxygen remains the same (20.9%), the partial pressure of oxygen decreases, reducing the amount of oxygen available for delivery to exercising tissues. Altitude classifications have been developed (Table 1) to roughly delineate altitudes at which different physiological changes and stressors are observed. 1 Several aspects related to endurance performance may be altered by hypoxic exposure and training including increases in erythrocyte volume, maximal aerobic exercise capacity, capillary density, and economy. ...

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... Faiss et al. and McLean et al. confirmed that the enhancement in endurance exercise performance following hypoxic training was more strongly related to exercise training performed using the high-intensity anaerobic interval method (Faiss et al., 2013;McLean et al., 2014). Therefore, the exercise protocol for improving endurance exercise performance mainly utilizes high-intensity interval exercises rather than moderate-intensity continuous exercises (McLean et al., 2014;Sinex and Chapman, 2015;Czuba et al., 2017;Park et al., 2018;Jung et al., 2020). ...
... Furthermore, a few previous studies have not supported the enhancement of endurance exercise performance following IHT (Katayama et al., 2004;Rodríguez et al., 2007;Roels et al., 2007;Beidleman et al., 2009). These conflicting results may be due to methodological differences, such as athletes' training status; type, volume, and intensity of training; hypoxic stimulus dose; and time point in the measurement of athletic performance following the hypoxic training procedure (McLean et al., 2014;Sinex and Chapman, 2015;Park et al., 2018). These previous studies used a relatively low exercise intensity during training and short exposure periods under hypoxia. ...
... Several previous studies using the LHTL regimen reported mean increases of 5-9% in red cell volume and >8% in Hb concentration (Levine and Stray-Gundersen, 1997;Rusko et al., 1999;Hahn et al., 2001;Stray-Gundersen et al., 2001). In a previous study (Sinex and Chapman, 2015), an LHTL regime residing at 2000-2,500 m or lower for 3-4 weeks with over 12 h of continuous altitude exposure per day appeared to be sufficient to activate an EPO response and RBC production. However, our study examined hematological parameters related to oxygen-transporting capacity using the IHT regime instead of the LHTL regime in amateur Korean female runners. ...
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Interval training under hypoxia (IHT) is commonly used to enhance endurance exercise performance. However, previous studies examining hematologic changes related to the immune system that affect health and conditioning are lacking. This study aimed to evaluate the effects of IHT for 6-weeks on hematological parameters, hemodynamic function, and endurance exercise performance in amateur Korean female runners. Twenty healthy amateur Korean female runners (age: 24.85 ± 3.84 years) were equally assigned to normoxic training group (NTG) for interval training under normoxia (760 mmHg) and hypoxic training group (HTG) for interval training under hypobaric hypoxia (526 mmHg, 3000 m simulated altitude) according to their body composition and endurance exercise performance. All participants performed 120-min of training sessions, consisting of 20-min of warm-up, 60-min of interval training, and 20-min of cool-down. The training program was performed 3-days per week for 6-weeks. Warm-up and cool-down were performed for 20-min at 60% maximal heart rate (HRmax). The interval training sessions comprised 10 repetitions of interval exercise (5-min of exercise corresponding to 90-95% HRmax and 1-min of rest) on a treadmill. All participants underwent measurements of hematological parameters, hemodynamic function, and endurance exercise performance before and after training. Both groups showed a significant increase in erythropoietin (EPO) level and a decrease in monocyte abundance, with EPO showing a greater increase in the HTG than in the NTG. B cell abundance significantly increased in the NTG; hematocrit and neutrophil counts significantly increased, and lymphocyte counts significantly decreased in the HTG. The HTG showed a significant improvement in oxygen uptake, stroke volume index, and end-diastolic volume index compared to the NTG. In addition, both groups showed significant improvements in heart rate, end-systolic volume index, and cardiac output index. The maximal oxygen uptake and 3000 m time trial record were significantly improved in both groups, and the HTG showed a tendency to improve more than the NTG. In conclusion, the IHT was effective in enhancing endurance exercise performance through improved hemodynamic function. Furthermore, hematological parameters of immune system showed a normal range before and after training and were not negatively affected.
... Acute and chronic exposures to altitude can affect both the physiological responses and the locomotor behavior of the human body (Mazzeo, 2008;West, 2017;Dietz and Hackett, 2019) The main effect of the ascent to altitude is a progressive reduction in the partial pressure of O 2 in the inspired air. It is well known that the reduced availability of O 2 is responsible for the reduction in performance during tasks where the predominant source of energy for muscle contraction is derived from the aerobic system (e.g., long-distance running) (Barnes and Kilding, 2015;Sinex and Chapman, 2015;Flaherty et al., 2016;Sharma et al., 2018;Mujika et al., 2019). Although acute exposure to altitude impairs endurance performance, chronic exposure to hypoxia can induce a number of cardiovascular and hematological adaptations that are potentially effective to enhance performance in endurance tasks (Steele et al., 2012;Wyatt, 2014;Burtscher et al., 2018). ...
... It is noteworthy that moderate altitude (1,500-3,500 m) is the condition most commonly used by athletes for their altitude training camps (Dietz and Hackett, 2019). In addition, there are a number of strategies for conducting altitude training camps, the most common of which are the following: (I) Live and train at altitude, (II) live at altitude and train at sea level, (III) live at altitude and train at both altitude and sea level, and (IV) live at sea level and train at altitude (Sinex and Chapman, 2015). Depending on the desired physiological adaptations and considering logistical constraints, athletes can choose the altitude training strategy that best fits their goals. ...
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The aim of the study was to test whether ascending to a moderate real altitude affects motoneuron pool excitability at rest, as expressed by a change in the H-reflex amplitude, and also to elucidate whether a possible alteration in the motoneuron pool excitability could be reflected in the execution of lower-body concentric explosive (squat jump; SJ) and fast eccentric-concentric (drop jump; DJ) muscle actions. Fifteen participants performed four experimental sessions that consisted of the combination of two real altitude conditions [low altitude (low altitude, 690 m), high altitude (higher altitude, 2,320 m)] and two testing procedures (H-reflex and vertical jumps). Participants were tested on each testing day at 8, 11, 14 and 17 h. The only significant difference (p < 0.05) detected for the H-reflex was the higher H-reflex response (25.6%) obtained 15 min after arrival at altitude compared to baseline measurement. In terms of motor behavior, DJ height was the only variable that showed a significant interaction between altitude conditions (LA and HA) and time of measurement (8, 11, 14 and 17 h) as DJ height increased more during successive measurements at HA compared to LA. The only significant difference between the LA and HA conditions was observed for DJ height at 17 h which was higher for the HA condition (p = 0.04, ES = 0.41). Although an increased H-reflex response was detected after a brief (15–20 min) exposure to real altitude, the effect on motorneuron pool excitability could not be confirmed since no significant changes in the H-reflex were detected when comparing LA and HA. On the other hand, the positive effect of altitude on DJ performance was accentuated after 6 h of exposure.
... Studies of many authors have shown that the training process conducted in conditions of altitude hypoxia is very effective for athletes practicing endurance and mixed sports [12][13][14][15]. Training in conditions of hypobaric hypoxia causes many physiological changes in the body. ...
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This study characterizes high-altitude training camps and their effect on the aerobic capacity of a Polish national team member (M.W.), who was a participant in the PyeongChang 2018 Winter Olympic Games (body weight: 59.6 kg, body height: 161.0 cm, fat mass: 10.9 kg and 18.3% of fat tissue, fat-free mass: 48.7 kg, muscle mass: 46.3 kg, and BMI = 23.0 kg/m 2). The tests were conducted in the periods from (pe-riod of general and special preparation). The study evaluated aerobic and anaerobic capacity determined by laboratory tests, a cardiopulmonary graded exercise test to exhaustion performed on a cycle ergometer (CPET), and the Wingate anaerobic test. Based on the research, training in hypo-baric conditions translated into significant improvements in the skater's exercise capacity recorded after participating in the Olympic Winter Games in Korea (February 2018). In the analyzed period (2018-2019), there was a significant increase in key parameters of aerobic fitness such as anaerobic threshold power output (AT-PO) [W]-223; power output POmax [W]-299 and AT-PO [W/kg]-3.50; (POmax) [W/kg]-4.69; and AT-VO2 [mL/kg/min]-51.3; VO2max [mL/kg/min]-61.0. The athlete showed high-exercise-induced adaptations and improvements in the aerobic metabolic potential after two seasons, in which four training camps were held in altitude conditions.
... Although altitude training elicits adaptive responses that enable physiological advantages during exercise in hypoxia, its benefits on sea-level performance are still being debated. While several studies reported hypoxic training increased endurance exercise performance, others reported no changes or even impaired aerobic capacity or performance after hypoxic training (Brocherie et al. 2015a;Czuba et al. 2011;Montero and Lundby 2017;Sinex and Chapman 2015). These discrepancies may stem from differences in hypoxic dose (a severity of altitude and total duration of the daily exposure) and training protocols employed by various studies, as well as differing in subjects' training status (trained vs. well-trained athletes) (Viscor et al. 2018). ...
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Objective To evaluate the effects of repeated sprint (RS) training in hypoxia on aerobic performance, repeated sprint ability (RSA), and muscle oxygenation in Rugby Sevens.Methods Fourteen Rugby Sevens players were randomly allocated into hypoxic (RSH, FIO2 = 14.5%, n = 7) or normoxic (RSN, FIO2 = 20.9%, n = 7) groups. Both groups underwent RS training consisting of 3 sets of 6-s × 10 sprints at 140% of velocity at peak oxygen uptake (\(vV{\text{O}}_{2} {\text{peak}}\)) on a motorized treadmill, 3 days/week for 6 weeks in addition to usual training. Hematological variables, hypoxia-inducible factor-1 alpha (HIF-1α), and vascular endothelial growth factor (VEGF) concentrations were measured. Aerobic performance, RSA, and muscle oxygenation during the running-based anaerobic sprint (RAS) test were analyzed.ResultsRSH caused no changes in hemoglobin concentration and hematocrit but significant improvements in \(V{\text{O}}_{2} {\text{peak}}\) (7.5%, p = 0.03, ES = 1.07), time to exhaustion (17.6%, p = 0.05, ES = 0.92), and fatigue index (FI, − 12.3%, p = 0.01, ES = 1.39) during the RSA test compared to baseline but not RSN. While ∆deoxygenated hemoglobin was significantly increased both after RSH and RSN (p < 0.05), ∆tissue saturation index (− 56.1%, p = 0.01, ES = 1.35) and ∆oxygenated hemoglobin (− 54.7%, p = 0.04, ES = 0.97) were significantly decreased after RSH. These changes were concomitant with increased levels of HIF-1α and VEGF in serum after RSH with a strong negative correlation between ∆FI and ∆deoxygenated hemoglobin after RSH (r = − 0.81, p = 0.03).Conclusion There was minimal benefit from adding RSH to standard Rugby Sevens training, in eliciting improvements in aerobic performance and resistance to fatigue, possibly by enhanced muscle deoxygenation and increased serum HIF-1α and VEGF concentrations.
... Nowadays, altitude/hypoxic training is becoming increasingly popular in sports [24][25][26][27]. Exposure to hypoxia leads to stimulation of HIF-1, which, apart from regulation of erythropoiesis and angiogenesis, is also a regulator of activity of glycolytic enzymes, mainly phosphofructokinase (PFK-1) [28,29]. ...
... However, hypoxia and subsequent reoxygenation are also responsible for ROS/RNS overproduction, during prolonged exposure to altitude, as well as during intermittent hypoxic training [29][30][31]. This is caused by disruption of the mitochondrial respiratory chain, disturbances in arachidonic acid metabolism, or migration/activation of immune cells during regular physical activity [24,25,30,31]. Nevertheless, there is a lack of studies evaluating the relationship between antioxidant systems, oxidative and nitrosative cell damage, inflammation, and lysosomal function under normoxic and hypoxic conditions. ...
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Hypoxia is a recognized inducer of oxidative stress during prolonged physical activity. Nevertheless, previous studies have not systematically examined the effects of normoxia and hypoxia during acute physical exercise. The study is aimed at evaluating the relationship between enzymatic and nonenzymatic antioxidant barrier, total antioxidant/oxidant status, oxidative and nitrosative damage, inflammation, and lysosomal function in different acute exercise protocols under normoxia and hypoxia. Fifteen competitive athletes were recruited for the study. They were subjected to two types of acute cycling exercise with different intensities and durations: graded exercise until exhaustion (GE) and simulated 30 km individual time trial (TT). Both exercise protocols were performed under normoxic and hypoxic (FiO 2 = 16:5%) conditions. The number of subjects was determined based on our previous experiment, assuming the test power = 0:8 and α = 0:05. We demonstrated enhanced enzymatic antioxidant systems during hypoxic exercise (GE: ↑ catalase (CAT), ↑ superoxide dismutase; TT: ↑ CAT) with a concomitant decrease in plasma reduced glutathione. In athletes exercising in hypoxia, redox status was shifted in favor of oxidation reactions (GE: ↑ total oxidant status, ↓ redox ratio), leading to increased oxidation/nitration of proteins (GE: ↑ advanced oxidation protein products (AOPP), ↑ ischemia-modified albumin, ↑ 3-nitrotyrosine, ↑ S-nitrosothiols; TT: ↑ AOPP) and lipids (GE: ↑ malondialdehyde). Concentrations of nitric oxide and its metabolites (peroxynitrite) were significantly higher in the plasma of hypoxic exercisers with an associated increase in inflammatory mediators (GE: ↑ myeloperoxidase, ↑ tumor necrosis factor-alpha) and lysosomal exoglycosidase activity (GE: ↑ N-acetyl-β-hexosaminidase, ↑ β-glucuronidase). Our study indicates that even a single intensive exercise session disrupts the antioxidant barrier and leads to increased oxidative and nitrosative damage at the systemic level. High-intensity exercise until exhaustion (GE) alters redox homeostasis more than the less intense exercise (TT, near the anaerobic threshold) of longer duration (20:2 ± 1:9 min vs. 61:1 ± 5:4 min-normoxia; 18:0 ± 1:9 min vs. 63:7 ± 3:0 min-hypoxia), while hypoxia significantly exacerbates oxidative stress, inflammation, and lysosomal dysfunction in athletic subjects.
... Endurance exercise is closely related by the oxygenation capacity of the active muscles [4]. Improved oxygenation capacity increases the efficiency of aerobic energy production and, therefore, advances exercise performance by increasing exercise intensity [5]. Also, hypoxic exercise stimulates athletic performance in aerobic events by increasing erythropoiesis and improving the oxygen-transporting and utilizing capacities [6]. ...
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Aim: We aimed to investigate the overall effects of hypoxic/normoxic exercise and hypoxia on redox status in both systemic circulation and brain, and to prove whether the variations in plasma redox status could affect the brain’s own redox homeostasis, vice versa. Methods: We designed hypoxic, normoxic exercise groups with their respective controls. We studied on redox status biomarkers i.e., hydroperoxide, low molecular weight thiols, protein thiols, total thiols, and advanced oxidation protein products in frontal cortex; total antioxidant and total oxidant status in the plasma. Results: There is no statistically significant difference observed in redox homeostasis of the brain after hypoxic and/or normoxic exercise or hypoxia itself with an increased systemic oxidant status. Conclusions: Live in hypoxia and exercise at normoxia might diminish the hazardous effect of ROS on the brain at hypoxia. From our findings, thiols, which are the indicators of the antioxidant power of the brain, are found to be protected in groups that are exposed to long-term hypoxia and exercise at normoxia. It might be possible that people who are exposed to hypoxia will be least affected by this damage with normoxic exercise, or even will not be affected at all. Keywords: Hypoxic exercise, Redox homeostasis, Brain, Plasma
... Since then, the effects of hypoxia on exercise performance have received considerable attention [1]. Exercise training under hypoxia has been widely accepted as a useful modality for improving athletic performance, and experimental evidence has been accumulated regarding the efficacy of hypoxic training [2][3][4][5][6]. Exercise under hypoxia decreases arterial oxygen saturation, which reduces the ability to deliver oxygen to active muscles [7]. ...
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We compared the effects of metabolic, cardiac, and hemorheological responses to submaximal exercise under light hypoxia (LH) and moderate hypoxia (MH) versus normoxia (N). Ten healthy men (aged 21.3 � 1.0 years) completed 30 min submaximal exercise corresponding to 60% maximal oxygen uptake at normoxia on a cycle ergometer under normoxia (760 mmHg), light hypoxia (596 mmHg, simulated 2000 m altitude), and moderate hypoxia (526 mmHg, simulated 3000 m altitude) after a 30 min exposure in the respective environments on different days, in a random order. Metabolic parameters (oxygen saturation (SPO2), minute ventilation, oxygen uptake, carbon dioxide excretion, respiratory exchange ratio, and blood lactate), cardiac function (heart rate (HR), stroke volume, cardiac output, and ejection fraction), and hemorheological properties (erythrocyte deformability and aggregation) were measured at rest and 5, 10, 15, and 30 min after exercise. SPO2 significantly reduced as hypoxia became more severe (MH > LH > N), and blood lactate was significantly higher in the MH than in the LH and N groups. HR significantly increased in the MH and LH groups compared to the N group. There was no significant difference in hemorheological properties, including erythrocyte deformability and aggregation. Thus, submaximal exercise under light/moderate hypoxia induced greater metabolic and cardiac responses but did not affect hemorheological properties.
... Dette var såkalt live high -train lowhøydetrening. Begge oppholdene økte antall røde blodceller med omtrent 4 prosent og forbedret prestasjonsevnen i 3 km løping i lavlandet med 1-2 prosent -noe som er typiske endringer i studier fra enkelte forskningsgrupper (Sinex og Chapman 2015). Det må her nevnes at andre ikke finner endringer i mengden røde blodceller eller utholdenhetsprestasjonsevnen hos idrettsutøvere, verken etter naturlig eller simulert høydetreningsopphold (Lundby, Mil-let, Calbet, Bartsch og Subudhi 2012;Lundby og Robach 2016;Robach m.fl. ...
... There are three major hypoxic training programs: live high-train high (LHTH), live high-train low (LHTL), and live low-train high (LLTH) (Wilber, 2007). LHTH and LHTL programs focus mainly on improving endurance performance, aerobic capacity, and erythrocyte volume/hemoglobin mass (Sinex & Chapman, 2015;Wilber, 2007), whereas LLTH program aims to enhance not only endurance performance and aerobic capacity, but also sprint performance and glycolytic capacity (Millet & Girard, 2017;Wilber, 2007). In LLTH training, exercise in hypoxia reduces O 2 delivery to skeletal muscle and increases glycolytic energy contribution. ...
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We investigated whether moderate‐intensity training of horses in moderate hypoxia for 4 weeks elicits greater adaptations in exercise performance, aerobic capacity, and glycolytic/oxidative metabolism in skeletal muscle compared to normoxic training. In a randomized crossover study design, seven untrained Thoroughbred horses (5.9 ± 1.1 years, 508 ± 9 kg) completed 4 weeks (3 sessions/week) of two training protocols consisting of 3‐min cantering at 70% of maximal oxygen consumption () in hypoxia (HYP; FIO2 = 14.7%) and normoxia (NOR; FIO2 = 21.0%) with a 4‐month washout period. Normoxic incremental exercise tests (IET) were conducted before and after training. Biopsy samples were obtained from the middle gluteal muscle before IET and monocarboxylate transporter (MCT) protein expression and glycolytic/mitochondrial enzyme activities were analyzed. Data were analyzed using mixed models (p < 0.05). Running speed was 7.9 ± 0.2 m/s in both groups and arterial oxygen saturation during training in NOR and HYP were 92.9 ± 0.9% and 75.7 ± 3.9%, respectively. Run time in HYP (+9.7%) and in both groups (NOR, +6.4%; HYP, +4.3%) at IET increased after 4 weeks of training. However, cardiac output, arterial‐mixed venous O2 difference, and hemoglobin concentration at exhaustion were unchanged in both conditions. While MCT1 protein and citrate synthase activity did not increase in both conditions after training, MCT4 protein (+13%), and phosphofructokinase activity (+42%) increased only in HYP. In conclusion, 4 weeks of moderate‐intensity hypoxic training improves exercise performance and glycolytic capacity of skeletal muscle in horses. Four weeks of moderate‐intensity training in hypoxia (70% 3 min, 3 sessions/week, FIO2 = 14.7%) increased run time and at incremental exercise tests, monocarboxylate transporter (MCT) 4 protein content and phosphofructokinase (PFK) activity of skeletal muscle in horses, whereas the same training in normoxia only increased .
... Altitude can be classified as near sea level (<500 m), low altitude (500-2,000 m), moderate altitude (2,000-3,000 m), high altitude (3,000-5,500 m), and extreme altitude (>5,500 m) above sea level [2]. As altitude increases, atmospheric pressure decreases, and the partial pressure of oxygen also decreases, thus the amount of oxygen available for delivery to exercising tissues will reduce [3,4]. ...
... ere are different models of altitude training: live hightrain high (LH-TH), live high-train low, live low-train high, and live high-train low and high [4,6]. Among them, the LH-TH method is the traditional concept of altitude training, practiced by athletes in East Africa. ...
... Altitudes that are too low are associated with the inadequate erythropoietic response [7,16,25]. Generally, in living high-training high approach, the optimal altitude to improve exercise performance is between 2,000 and 2,500 m above sea level [4,26]. ...
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Introduction. Endurance running performance is dependent upon hematological, physiological, anthropometrical, diet, genetic, and training characteristics. Increased oxygen transport and efficiency of tissue in extracting oxygen are the major determinants to competitions that require endurance. Thus, altitude training is often employed to increase blood oxygen-carrying capacity to improve sea-level endurance performance. This study aimed to compare hematological parameters of endurance runners’ training at different clubs with different altitudes (Guna Athletics Sport Club at Guna (3100 meter above sea level) and Ethiopian Youth Sport Academy at Addis Ababa (2400 meter above sea level)). Methods. A comparative cross-sectional study was conducted at GASC and EYSA. Data were collected from a total of 102 eligible study subjects (26 runners and 25 controls at Guna and 26 runners and 25 controls at Addis Ababa) from May to October 2019. About 3 ml of the venous blood was drawn from the antecubital vein by aseptic procedure and analyzed using a hematology analyzer (DIRUI BCC-3000B, China). One-way ANOVA and independent-sample t-tests were used to compare means. Result. Male runners in Guna had significantly higher hemoglobin (Hgb), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and white blood cell (WBC) count than male runners in Addis Ababa. Besides, female runners in Guna had significantly higher MCH and MCHC than female runners in Addis Ababa. However, there were no significant differences between Guna and Addis Ababa runners in red blood cell (RBC) count, Hct, MCV, and platelet count in both sexes, while Hgb and WBC count in females. Conclusion. Decisively, Guna Athletics Sport Club endurance runners had significantly higher hematological parameters than Ethiopian Youth Sport Academy endurance runners. This provides invaluable information for coaches and sport physicians to monitor the hematological profile and the health status of an athlete living and training at different altitudes. 1. Introduction Running is one of the most popular sporting events worldwide, and running events range from sprints of 60 meters (m) to ultramarathons covering greater than 42.195 kilometers [1]. The International Association of Athletics Federation classified running as short distance (below 800 m), middle distance (800–3000 m), and long distance (3000-ultramarathon (>marathon)). Endurance running is highly dependent on the aerobic capacity and running economy [1]. Altitude can be classified as near sea level (<500 m), low altitude (500–2,000 m), moderate altitude (2,000–3,000 m), high altitude (3,000–5,500 m), and extreme altitude (>5,500 m) above sea level [2]. As altitude increases, atmospheric pressure decreases, and the partial pressure of oxygen also decreases, thus the amount of oxygen available for delivery to exercising tissues will reduce [3, 4]. Altitude training is aimed at increasing the oxygen-carrying capacity of blood to improve sea-level endurance performance in athletes. Increasing erythropoietin production in hypoxia, a hormone-stimulating erythropoiesis, is a key factor in the achievement of enhanced oxygen-carrying capacity of the blood. Rates of erythropoietin production and erythropoiesis depend on the duration and degree of exposure to hypoxia. Furthermore, many other factors may affect the hematological response to altitude training [5]. Currently, altitude training has become part of the standard training protocol in many aerobic sports to increase endurance performance in athletes or to acclimatize before competitions at altitude or before ascending to altitude [3, 6, 7]. Acute or chronic exposure of the human body to a hypoxic environment induces several adaptations that can lead to improved athletes’ performance at sea level. The mechanisms to improve exercise performance including hematological [8–10], cardiovascular, or ventilatory changes were induced by altitude training. However, altitude training can also lead to improved muscle buffering capacity, enhanced capillary density, and muscle mitochondrial volume [11–14]. Previous studies have shown that after altitude training of LH-TH or LH-TL there were increased red cell mass, total hemoglobin mass, reticulocytes, red blood cell (RBC) count, hemoglobin (Hgb), and hematocrit (Hct) from pre-altitude value [11, 15–20]. However, other studies did not show an increase in red cell mass, total hemoglobin mass, reticulocytes, RBC count, Hgb, and Hct after altitude training [21, 22]. Individual variation in response to altitude exposure is an important factor that needs to be accounted for when planning altitude training [5, 10, 15, 23]. There are different models of altitude training: live high-train high (LH-TH), live high-train low, live low-train high, and live high-train low and high [4, 6]. Among them, the LH-TH method is the traditional concept of altitude training, practiced by athletes in East Africa. In this model, athletes live and train at moderate altitudes 2,000–3,000 m above sea level that is thought to stimulate hematological and nonhematological responses [6, 7, 24]. This method is still in use today in particular in countries with natural altitude environments, including Kenya and Ethiopia [7, 17]. Athletes employing LH-TH are not able to train at an equivalent or near-equivalent intensity as at sea level [7, 16, 17, 25]. Altitudes that are too low are associated with the inadequate erythropoietic response [7, 16, 25]. Generally, in living high-training high approach, the optimal altitude to improve exercise performance is between 2,000 and 2,500 m above sea level [4, 26]. Different hematological, physiological, anthropometrical, diet, genetic, motivation, and training characteristics influence endurance running performances, depending on the length and duration of the performance training [27–34]. Factors that have been proposed to explain the dominance of East African athletes, particularly the success of the Kenyan and Ethiopian distance runners, include genetic predisposition, favorable skeletal-muscle-fiber composition, oxidative enzyme profile, development of high maximal oxygen uptake, relatively high Hct and Hgb, good metabolic “economy”, traditional Kenyan/Ethiopian diet, living and training at altitude, and motivation to achieve economic success [29, 30, 33, 35–39]. There is increasing support for the role of hematological variables like RBC count, Hgb, Hct, total hemoglobin mass, and blood volume in determining endurance performance [29, 31, 40, 41]. Since the availability of oxygen in skeletal muscle impacts endurance performance, it is essential to monitor hematological parameters to detect the oxygen transport capacity of endurance athletes [42, 43]. Ethiopia has many altitudinous areas ranging from 1500 m to 4550 m above sea level; however, athletes are emerging from a specific area and population particularly from Arsi and Shewa [29, 30, 39]. There are no published data to support or refute that Hgb and total blood volume in Ethiopian athletes are uniquely different from other elite running populations [29]. Unique hematological fluctuations observed in an athlete population provide invaluable information to the sports physician monitoring the health status of an athlete [10]. To the best of our knowledge, no study compared hematological parameters of Ethiopian endurance runners training at various clubs that are located at different altitudes. Therefore, this study compared hematological parameters in endurance runners of Guna Athletics Sport Club, which is located in Northern Ethiopia at 3100 m above sea level, and Ethiopian Youth Sport Academy, which is located in the central part of Ethiopia (Addis Ababa, the capital city of Ethiopia) at 2400 m above sea level. The two clubs use a live high-train high model, yet the altitude varies (3100 m vs 2400 m above sea level). Our hypothesis was there is no significant difference in hematological parameters between Guna Athletics Sport Club and Ethiopian Youth Sport Academy endurance runners. 2. Methods 2.1. Study Area, Period, and Design A comparative institutional-based cross-sectional study design was employed to conduct the study from May to October 2019 in two training camps in Ethiopia, Guna Athletics Sport Club and Ethiopian Youth Sport Academy. Guna Athletics Sport Club is located in the Amhara region, South Gondar zone, near Guna Mountain (nearly 4200 m above sea level), which is 695 km far from Addis Ababa. This training camp is particularly situated at an altitude of 3045 m above sea level, and routine training takes place at 3100 m above sea level. The second study area was Ethiopian Youth Sport Academy, which is located in Addis Ababa, at approximately an altitude of 2400 m above sea level. 2.2. Study Population All endurance runners in GASC and EYSA fulfilling the eligibility criteria were taken as the study population. 2.3. Sampling Procedures A total of 102 study subjects participated in this study. A total of 26 endurance runners from each training camp and 25 matched nonathletes were recruited outside each training camp. Based on sex, 18 male and 8 female endurance runners were involved from each camp, and 18 male and 7 matched female nonathletes were involved from each camp. A convenient nonprobability sampling technique was used to select eligible study subjects. 2.4. Eligibility Criteria Both male and female athletes who were middle- and long-distance runners ranging from 800 m to marathon, as well as those in the age range of 15 to 35 years were included in the study. However, athletes in Addis Ababa whose root is from northern training camps (Amhara region); athletes in Guna whose root is from Addis Ababa (Oromia region); athletes who were reported to have known cancer, kidney disease, liver disease, HIV/AIDS, cardiac diseases, anemia, and respiratory diseases (like asthma); smokers; athletes trained less than 5 days; athletes on vacation; and pregnant during the data collection period were excluded from the study. 2.5. Study Variables In the present study, running performance or the International Association of Athletics Federation score (IAAF score) was taken as the dependent variable, while sociodemographic variables such as age, sex, marital status, and religion, anthropometric parameters, including weight, height, and body mass index, and hematological parameters such as RBC count, Hct, Hgb, MCV, MCH, MCHC, WBC count, and platelet count were considered independent variables. 2.6. Operational Definitions Elite athlete: professional runner who is competing at the national or international level. Endurance runners: runners who run from 800 m to ultramarathon. Middle-distance running: running covering the distance from 800 m to 3000 m. Long-distance running: running covering the distance from 3000 m to ultramarathon. International Association of Athletics Federation score (IAAF score): it is the measure of an athlete’s performance, and this score can be used to determine the result score of performance for the world rankings, to evaluate competitions, and to establish the best athlete award in a specific competition [44]. Total hemoglobin mass: it is the absolute mass of circulating hemoglobin in the body. 2.7. Data Collection Procedures After informed consent, sociodemographic data were collected by using structured questionnaires from the selected participants through face-to-face interviews. Then, the height of the study participants was measured without shoes using a stadiometer and rounded to the nearest one cm, whereas the weight of subjects was measured using a weighing scale to the nearest 0.1 kg with light clothing, without phones and shoes or any encumbrance that could alter their appropriate weight. Body mass index (BMI) was calculated by dividing weight (in kg) by height (in meters) squared. By following the aseptic procedure, about 3 ml of the venous blood sample was drawn from the antecubital vein of each participant by a trained and qualified laboratory technologist after overnight fasting. The blood sample in the Guna training camp was collected using EDTA-coated vacutainer tubes, and it was then transported in sealed boxes to Bahir Dar within an hour of blood collection and at room temperature. The laboratory analysis was done at Afilas Primary Hospital in Bahir Dar using (DIRUI BCC-3000B; China) a hematology analyzer within 5 hours of the blood sample collection. Similarly, samples at the Addis Ababa training camp were collected using EDTA-coated vacutainer tubes, and then the laboratory analysis was done within an hour of sample collection at the clinic in the center using a similar automated blood analyzer. Performance of runners was measured using the IAAF score, which was taken from the IAAF score table (2017) by using personal best time. It was also checked by the online IAAF scoring calculator. Tables are normally valid for performances worth between 0 and 1400 points [44]. 2.8. Data Processing and Statistical Analysis The data collected were coded, cleaned, entered, and analyzed using Statistical Package for Social Sciences (SPSS), version 25.0. Categorical variables were presented using frequency and percent, whereas continuous variables were summarized using mean (x̅) and standard deviation (SD). The analysis of the differences in means of study variables was evaluated using an independent-sample t-test and one-way ANOVA. We used Levene’s test to assess the homogeneity of variance, and the Tukey and Games–Howell post hoc tests were used if Levene’s test was nonsignificant and significant, respectively. Those variables with a -value of <0.05, at a 95% confidence interval (CI), were considered statistically significant. The result of males and females were summarized separately. 3. Results 3.1. Sociodemographic Data The total study participants were 102 (51 from Guna Athletics Sport Club (Guna) and 51 from Ethiopian Youth Sport Academy (Addis Ababa), among them 72 (70.6%) were males and 30 (29.4%) were females. There were 52 athletes (26 from each camp) and 50 nonathletes (25 from each camp). Out of 26 athletes in Guna (AG), 18 (69.2%) were males and 8 (30.8%) were females. Also from 25 nonathletes in Guna (NAG), 18 (72%) and 7 (28%) were males and females, respectively. Athletes in Addis Ababa (AAA) were 26, of these 18 (69.2%) were males and 8 (30.8%) were females. Nonathletes in Addis Ababa (NAAA) were 25, among them 18 (72%) and 7 (28%) were males and females, respectively. Among 102 participants, 51 (50%) were from Oromia, and 51 (50%) were from the Amhara region. The mean ages of study groups for both sexes are presented in Table 1. The majority of male and female subjects in both groups belonged to the age bracket of 15–19 and 20–24 years, respectively. One-way ANOVA showed there were no significant differences in mean ages between AG vs AAA, AG vs NAG, and AAA vs NAAA for both sexes (Table 1). Moreover, there were no significant differences in height, weight, and BMI between AG and AAA in both sexes. Regarding marital status, the majority of AG 25 (96.2%), AAA 23 (88.5%), NAG 23 (92%), and NAAA (84%) were single. The majority of AG 20 (76.9%), AAA 12 (46.2%), NAG 13 (52%), and NAAA 12 (48%) attended secondary and preparatory school. The majority of AG (96.2%), NAG (100%), and NAAA (64%) were orthodox Christians; however, most of the athletes in Addis Ababa (46.2%) were protestant Christians. Variables AG AAA NAG NAAA Male Age (yrs) 23.3 ± 3.7 24.2 ± 3.9 21.2 ± 3.7 26.3 ± 3.3 Height (cm) 169.9 ± 4.1 b 172 ± 8.9 162.6 ± 6.4 b 169.8 ± 6.5 Weight (kg) 56.3 ± 6.3 58.8 ± 6.1 53.5 ± 7 64.6 ± 7.9 BMI (kg/m²) 19.4 ± 1.6 19.9 ± 1.6 c 20.2 ± 1.6 22.4 ± 2.7 c Female Age 19.9 ± 1.5 20.4 ± 3.4 21.9 ± 3.4 23.4 ± 2.1 Height 159.9 ± 5 164 ± 5 159.3 ± 10 165.6 ± 5.8 Weight 46.8 ± 3 51.4 ± 6.7 52.3 ± 4.6 60 ± 9.7 BMI 18.3 ± 1.3 19.2 ± 1.7 20.7 ± 1.6 21.9 ± 3.4 Abbreviations: AG, athletes in Guna; NAG, nonathletes in Guna; AAA, athletes in Addis Ababa; NAAA, nonathletes in Addis Ababa; b, AG vs NAG; c, AAA vs NAAA; ; .