The Impact of Normobaric Hypoxia and Intermittent Hypoxic Training on Cardiac Biomarkers in Endurance Athletes: A Pilot Study.

This study explores the effects of normobaric hypoxia and intermittent hypoxic training (IHT) on the physiological condition of the cardiac muscle in swimmers. Hypoxia has been reported to elicit both beneficial and adverse changes in the cardiovascular system, but its impact on the myocardium during acute exercise and altitude/hypoxic training remains less understood. We aimed to determine how a single bout of intense interval exercise and a four-week period of high-intensity endurance training under normobaric hypoxia affect cardiac marker activity in swimmers. Sixteen young male swimmers were divided into two groups: one undergoing training in hypoxia and the other in normoxia. Cardiac markers, including troponin I and T (cTnI and cTnT), heart-type fatty acid-binding protein (H-FABP), creatine kinase-MB isoenzyme (CK-MB), and myoglobin (Mb), were analyzed to assess the myocardium's response. We found no significant differences in the physiological response of the cardiac muscle to intense physical exertion between hypoxia and normoxia. Four weeks of IHT did not alter the resting levels of cTnT, cTnI, and H-FABP, but it resulted in a noteworthy decrease in the resting concentration of CK-MB, suggesting enhanced cardiac muscle adaptation to exercise. In contrast, a reduction in resting Mb levels was observed in the control group training in normoxia. These findings suggest that IHT at moderate altitudes does not adversely affect cardiac muscle condition and may support cardiac muscle adaptation, affirming the safety and efficacy of IHT as a training method for athletes.

The effect of normobaric hypoxia on acute exercise-induced changes in blood sphingoid base-1-phosphates metabolism in cyclists.

Extracellular sphingosine-1-phosphate (S1P) emerged as an important regulator of muscle function. We previously found that plasma S1P concentration is elevated in response to acute exercise and training. Interestingly, hypoxia, which is commonly utilized in training programs, induces a similar effect. Therefore, the aim of the current study was to determine the effect of normobaric hypoxia on exercise-induced changes in blood sphingolipid metabolism. Fifteen male competitive cyclists performed a graded cycling exercise until exhaustion (GE) and a simulated 30 km individual time trial (TT) in either normoxic or hypoxic (FiO2 = 16.5%) conditions. Blood samples were taken before the exercise, following its cessation, and after 30 min of recovery. We found that TT increased dihydrosphingosine-1-phosphate (dhS1P) concentration in plasma (both HDL- and albumin-bound) and blood cells, as well as the rate of dhS1P release from erythrocytes, regardless of oxygen availability. Plasma concentration of S1P was, however, reduced during the recovery phase, and this trend was augmented by hypoxia. On the other hand, GE in normoxia induced a selective increase in HDL-bound S1P. This effect disappeared when the exercise was performed in hypoxia, and it was associated with reduced S1P level in platelets and erythrocytes. We conclude that submaximal exercise elevates total plasma dhS1P concentration via increased availability of dihydrosphingosine resulting in enhanced dhS1P synthesis and release by blood cells. Maximal exercise, on the other hand, induces a selective increase in HDL-bound S1P, which is a consequence of mechanisms not related to blood cells. We also conclude that hypoxia reduces post-exercise plasma S1P concentration.

Hepcidin and erythroferrone response to 3 weeks of exposure to normobaric hypoxia at rest in trained cyclists.

Purpose: The effectiveness of altitude training on haematological adaptations is largely dependent on iron metabolism. Hepcidin and erythroferrone (ERFE) are key iron-regulating hormones, yet their response to altitude training is poorly understood. The aim of this study was to analyze changes in hepcidin and ERFE under the influence of 3 weeks of the Live High-Train Low (LH-TL) method. Methods: Twenty male trained cyclists completed a 3-week training program under normoxic conditions (NORM) or with passive exposure to normobaric hypoxia (LH-TL; FiO2 = 16.5%, ∼2000 m; 11-12 h/day). Hepcidin, ERFE, hypoxia inducible factor-2 (HIF-2), ferroportin (Fpn), erythropoietin (EPO), serum iron (Fe) and hematological variables were assessed at baseline (S1), then immediately after (S2) and 3 days after (S3) intervention. Results: In the LH-TL group, hepcidin decreased by 13.0% (p < 0.001) in S2 and remained at a reduced level in S3. ERFE decreased by 28.7% (p < 0.05) in S2 and returned to baseline in S3. HIF-2α decreased gradually, being lower by 25.3% (p < 0.05) in S3. Fpn decreased between S1 and S2 by 18.9% (p < 0.01) and remained lower during S3 (p < 0.01). In the NORM group, in turn, hepcidin levels increased gradually, being higher by 73.9% (p < 0.05) in S3 compared to S1. No statistically significant differences in EPO were observed in both groups. Conclusion: Three weeks of LH-TL suppresses resting hepcidin and ERFE levels in endurance athletes. We found no association between hepcidin and ERFE after LH-TL. Probably, ERFE is not the only factor that suppresses hepcidin expression in response to moderate hypoxia, especially in later stages of hepcidin downregulation. With the cessation of hypoxia, favorable conditions for increasing the availability of iron cease.

The Effects of Six-Gram D-Aspartic Acid Supplementation on the Testosterone, Cortisol, and Hematological Responses of Male Boxers Subjected to 11 Days of Nocturnal Exposure to Normobaric Hypoxia.

The aim of this study was to evaluate the effects of D-aspartic acid (DAA) supplementation during a simulated altitude protocol on the hormonal and hematological responses in athletes. We hypothesized that DAA supplementation would contribute to an increase in the luteinizing hormone (LH), free, and testosterone and a greater increase in hematological variables. Sixteen male boxers participated; they were randomly assigned to an experimental group (DAA) or a control group (C) and underwent 14 days of supplementation, 6 g/day of DAA. Both DAA and C participants were exposed to normobaric hypoxia (FiO2 = 15.5%; 2500 m) for 10-12 h a day over a period of 11 days. The results showed that DAA had no significant effect on resting, LH, or the testosterone/cortisol ratio during the training camp. Hypoxic exposure significantly (p < 0.05) increased red blood cell and reticulocyte counts as well as hemoglobin and hematocrit concentrations in both groups, but DAA had no significant effect on these changes. In conclusion, we found that DAA supplementation at a dose of 6 g/day for 14 days does not affect the testosterone, cortisol, or hematological responses of athletes during.

Chronic Exposure to Normobaric Hypoxia Increases Testosterone Levels and Testosterone/Cortisol Ratio in Cyclists.

The aim of this study was to analyze the effects of the "live high, train low" method (LH−TL) and intermittent hypoxic training (IHT) on testosterone (T) and cortisol (C) levels in cyclists. Thirty cyclists participated in the experiment. The LH−TL group (n = 10) was exposed to normobaric hypoxia (FiO2 = 16.3%) for 11−12 h a day and trained in normoxia for 3 weeks. In the IHT group (n = 10), participants followed the IHT routine three times a week for 3 weeks in normobaric hypoxia (FiO2 = 16.3%). The control group (N; n = 10) followed the same training protocol in normoxia. The LH−TL training was found to significantly increase (p < 0.05) T levels and the testosterone/cortisol (T/C) ratio during the experiment. The area under the curve (AUC) calculated for T levels over 4 weeks was significantly (p < 0.05) higher in the LH−TL group, by 25.6%, compared to the N group. The results also indicated a significant correlation (r = 0.53; p < 0.05) between AUC for T levels over 4 weeks and ∆ values of hemoglobin (HGB) in the LH−TL group. Overall, the findings show that LH−TL training at a moderate simulated altitude contributes to an increase in T levels and T/C ratio in athletes, which is a beneficial change stimulating anabolic processes and erythropoiesis.

Effect of Normobaric Hypoxia on Alterations in Redox Homeostasis, Nitrosative Stress, Inflammation, and Lysosomal Function following Acute Physical Exercise.

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 (FiO2 = 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-ß-hexosaminidase, ↑ ß-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.

Effects of Short-Term Phosphate Loading on Aerobic Capacity under Acute Hypoxia in Cyclists: A Randomized, Placebo-Controlled, Crossover Study.

The aim of this study was to evaluate the effects of sodium phosphate (SP) supplementation on aerobic capacity in hypoxia. Twenty-four trained male cyclists received SP (50 mg·kg-1 of FFM/day) or placebo for six days in a randomized, crossover study, with a three-week washout period between supplementation phases. Before and after each supplementation phase, the subjects performed an incremental exercise test to exhaustion in hypoxia (FiO2 = 16%). Additionally, the levels of 2,3-diphosphoglycerate (2,3-DPG), hypoxia-inducible factor 1 alpha (HIF-1α), inorganic phosphate (Pi), calcium (Ca), parathyroid hormone (PTH) and acid-base balance were determined. The results showed that phosphate loading significantly increased the Pi level by 9.0%, whereas 2,3-DPG levels, hemoglobin oxygen affinity, buffering capacity and myocardial efficiency remained unchanged. The aerobic capacity in hypoxia was not improved following SP. Additionally, our data revealed high inter-individual variability in response to SP. Therefore, the participants were grouped as Responders and Non-Responders. In the Responders, a significant increase in aerobic performance in the range of 3-5% was observed. In conclusion, SP supplementation is not an ergogenic aid for aerobic capacity in hypoxia. However, in certain individuals, some benefits can be expected, but mainly in athletes with less training-induced central and/or peripheral adaptation.

The Effects of Sodium Phosphate Supplementation on the Cardiorespiratory System and Gross Efficiency during Exercise under Hypoxia in Male Cyclists: A Randomized, Placebo-Controlled, Cross-Over Study.

The main aim of this study was to evaluate the effects of six days of tri-sodium phosphate (SP) supplementation on the cardiorespiratory system and gross efficiency (GE) during exercise under hypoxia in cyclists. Twenty trained male cyclists received SP (50 mg·kg-1 of fat-free mass/day) or placebo for six days in a randomized, cross-over study, with a three-week washout period between supplementation phases. Before and after each supplementation phase, the subjects performed an incremental exercise test to exhaustion under normobaric hypoxia (FiO2 = 16%, ~2500 m). It was observed that short-term SP supplementation led to a decrease in heart rate, an increase in stroke volume, and an improvement in oxygen pulse (VO2/HR) during low and moderate-intensity exercise under hypoxia. These changes were accompanied by an increase in the serum inorganic phosphate level by 8.7% (p < 0.05). No significant changes were observed in serum calcium levels. GE at a given workload did not change significantly after SP supplementation. These results indicated that SP promotes improvements in the efficiency of the cardiorespiratory system during exercise in a hypoxic environment. Thus, SP supplementation may be beneficial for endurance exercise in hypoxia.

Exposure to Normobaric Hypoxia Combined with a Mixed Diet Contributes to Improvement in Lipid Profile in Trained Cyclists.

This study aimed to analyze the effects of live high-train low method (LH-TL) and intermittent hypoxic training (IHT) with a controlled mixed diet on lipid profile in cyclists. Thirty trained male cyclists at a national level with at least six years of training experience participated in the study. The LH-TL group was exposed to hypoxia (FiO2 = 16.5%) for 11-12 h a day and trained under normoxia for 3 weeks. In the IHT group, participants followed the IHT routine three times a week under hypoxia (FiO2 = 16.5%) at lactate threshold intensity. The control group (N) lived and trained under normoxia. The results showed that the 3-week LH-TL method significantly improved all lipid profile variables. The LH-TL group showed a significant increase in HDL-C by 9.0% and a decrease in total cholesterol (TC) by 9.2%, LDL-C by 18.2%, and triglycerides (TG) by 27.6%. There were no significant changes in lipid profiles in the IHT and N groups. ∆TG and ∆TC were significantly higher in the LH-TL group compared to the N group. In conclusion, hypoxic conditions combined with a mixed diet can induce beneficial changes in lipid profile even in highly trained athletes. The effectiveness of the hypoxic stimulus is closely related to the hypoxic training method.

Red Blood Cell 2,3-Diphosphoglycerate Decreases in Response to a 30 km Time Trial Under Hypoxia in Cyclists.

Red blood cell 2,3-diphosphoglycerate (2,3-DPG) is one of the factors of rightward-shifted oxygen dissociation curves and decrease of Hb-O2 affinity. The reduction of Hb-O2 affinity is beneficial to O2 unloading at the tissue level. In the current literature, there are no studies about the changes in 2,3-DPG level following acute exercise in moderate hypoxia in athletes. For this reason, the aim of this study was to analyze the effect of prolonged intense exercise under normoxic and hypoxic conditions on 2,3-DPG level in cyclists. Fourteen male trained cyclists performed a simulation of a 30 km time trial (TT) in normoxia and normobaric hypoxia (FiO2 = 16.5%, ~2,000 m). During the TT, the following variables were measured: power, blood oxygen saturation (SpO2), and heart rate (HR). Before and immediately after exercise, the blood level of 2,3-DPG and acid-base equilibrium were determined. The results showed that the mean SpO2 during TT in hypoxia was 8% lower than in normoxia. The reduction of SpO2 in hypoxia resulted in a decrease of average power by 9.6% (p < 0.001) and an increase in the 30 km TT completion time by 3.8% (p < 0.01) compared to normoxia. The exercise in hypoxia caused a significant (p < 0.001) decrease in 2,3-DPG level by 17.6%. After exercise in normoxia, a downward trend of 2,3-DPG level was also observed, but this effect was not statistically significant. The analysis also revealed that changes of acid-base balance were significantly larger (p < 0.05) after exercise in hypoxia than in normoxia. In conclusion, intense exercise in hypoxic conditions leads to a decrease in 2,3-DPG concentration, primarily due to exercise-induced acidosis.

Comparison of maximal lactate steady state with anaerobic threshold determined by various methods based on graded exercise test with 3-minute stages in elite cyclists.

BACKGROUND: The maximal lactate steady state (MLSS) is defined as the highest workload that can be maintained for a longer period of time without continued blood lactate (LA) accumulation. MLSS is one of the physiological indicators of aerobic performance. However, determination of MLSS requires the performance of a series of constant-intensity tests during multiple laboratory visits. Therefore, attempts are made to determine MLSS indirectly by means of anaerobic threshold (AT) evaluated during a single graded exercise test (GXT) until volitional exhaustion. The aim of our study was to verify whether AT determined by maximal deviation (Dmax), modified maximal deviation (ModDmax), baseline LA concentration + 1 mmol/l (+ 1 mmol/l), individual anaerobic threshold (IAT), onset of blood lactate accumulation (OBLA4mmol/l) and V-slope methods based on GXT with 3-min stages provide valid estimates of MLSS in elite cyclists. METHODS: Twelve elite male cyclists (71.3 ± 3.6 ml/kg/min) completed GXT (the increase by 40 W every 3 min) to establish the AT (by Dmax, ModDmax, + 1 mmol/l, IAT, OBLA4mmol/l and V-slope methods). Next, a series of 30-min constant-load tests to determine MLSS was performed. Agreement between the MLSS and workload (WR) at AT was evaluated using the Bland-Altman method. RESULTS: The analysis revealed a very high (rs > 0.90, p < 0.001) correlation between WRMLSS and WRDmax and WRIAT. The other AT methods were highly (rs > 0.70) correlated with MLSS except for OBLA4mmol/l (rs = 0.67). The Bland-Altman analysis revealed the highest agreement with MLSS for the Dmax, IAT and + 1 mmol/l methods. Mean difference between WRMLSS and WRDmax, WRIAT and WR+1mmol/l was 1.7 ± 3.9 W, 4.3 ± 7.9 W and 6.7 ± 17.2 W, respectively. Furthermore, the WRDmax and WRIAT had the lowest limits of agreement with the WRMLSS. The ModDmax and OBLA4mmol/l methods overestimated MLSS by 31.7 ± 18.5 W and 43.3 ± 17.8 W, respectively. The V-slope method underestimated MLSS by 36.2 ± 10.9 W. CONCLUSIONS: The AT determined by Dmax and IAT methods based on the cycling GXT with 3-min stages provides a high agreement with the MLSS in elite cyclists. Despite the high correlation with MLSS and low mean difference, the AT determined by + 1 mmol/l method may highly overestimate or underestimate MLSS in individual subjects. The individual MLSS cannot be properly estimated by V-slope, ModDmax and OBLA4mmol/l methods.

Exercise-Induced Elevated BDNF Level Does Not Prevent Cognitive Impairment Due to Acute Exposure to Moderate Hypoxia in Well-Trained Athletes.

Exposure to acute hypoxia causes a detrimental effect on the brain which is also manifested by a decrease in the ability to perform psychomotor tasks. Conversely, brain-derived neurotrophic factor (BDNF), whose levels are elevated in response to exercise, is a well-known factor in improving cognitive function. Therefore, the aim of our study was to investigate whether the exercise under hypoxic conditions affects psychomotor performance. For this purpose, 11 healthy young athletes performed a graded cycloergometer exercise test to volitional exhaustion under normoxia and acute mild hypoxia (FiO2 = 14.7%). Before, immediately after exercise and after a period of recovery, choice reaction time (CRT) and number of correct reactions (NCR) in relation to changes in serum BDNF were examined. Additionally, other selected factors which may modify BDNF production, i.e., cortisol (C), nitrite, catecholamines (adrenalin-A, noradrenaline-NA, dopamine-DA, serotonin-5-HT) and endothelin-1 (ET-1), were also measured. Exercise in hypoxic conditions extended CRT by 13.8% (p < 0.01) and decreased NCR (by 11.5%) compared to rest (p < 0.05). During maximal workload, NCR was lower by 9% in hypoxia compared to normoxia (p < 0.05). BDNF increased immediately after exercise in normoxia (by 29.3%; p < 0.01), as well as in hypoxia (by 50.0%; p < 0.001). There were no differences in BDNF between normoxia and hypoxia. Considering the fact that similar levels of BDNF were seen in both conditions but cognitive performance was suppressed in hypoxia, acute elevation of BDNF did not compensate for hypoxia-induced cognition impairment. Moreover, neither potentially negative effects of C nor positive effects of A, DA and NO on the brain were observed in our study.

Changes in erythropoietin and vascular endothelial growth factor following the use of different altitude training concepts.

BACKGROUND: Erythropoietin (EPO) and vascular endothelial growth factor (VEGF) are important factors regulating erythropoiesis and angiogenesis. Altitude/hypoxic training may induce elevated VEGF-A and EPO levels. However, it appears that the range of adaptive changes depends largely on the training method used. Therefore, we investigated the changes in EPO and VEGF-A levels in athletes using three different altitude/hypoxic training concepts. METHODS: Thirty-four male cyclists were randomly divided into four groups: LH-TL group ("live high-train low" protocol), HiHiLo ("live high - base train high - interval train low" procedure), IHT ("intermittent hypoxic training") and control group (CN, normoxic training). The same 4-week training program was used in all groups. Blood samples were taken before and after each training week in order to evaluate serum EPO and VEGF-A levels. RESULTS: In the LH-TL and HiHiLo groups, EPO increased (P<0.001) after 1st week and remained elevated until 3rd week of altitude training. In the IHT and CN groups, EPO did not change significantly. VEGF-A was higher (P<0.001) after 2nd and 3rd week of training in the IHT group. In the HiHiLo group, VEGF-A changed (P<0.05) only after 3rd week. No significant changes of VEGF-A were noted in the LH-TL and CN groups. CONCLUSIONS: Altitude/hypoxic training is effective in increasing VEGF-A and EPO levels. However, a training method plays a key role in the pattern of adaptations. EPO level increase only when an adequate hypoxic dose is provided, whereas VEGF-A increases when the hypoxic exposure is combined with exercise, particularly at high intensity.

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

The main objective of this research was to evaluate the efficacy of intermittent hypoxic training (IHT) on aiming performance and aerobic capacity in biathletes. Fourteen male biathletes were randomly divided into a hypoxia group (H) (n = 7), which trained three times per week in a normobaric hypoxic environment (FiO2 = 16.5%, 2000 m a.s.l.) with lactate threshold intensity (LT) determined in hypoxia, and a control group (C) (n = 7), which exercised under normoxic conditions with LT intensity determined in normoxia. The training program included three weekly microcycles, followed by three days of recovery. The main part of the interval workout consisted of four 7 min (1st week), 8 min (2nd week), or 9 min (3rd week) running bouts at treadmill separated by 2 minutes of active recovery. After the warm-up and during the rest between the bouts, the athletes performed aiming to the target in the standing position with a sporting rifle (20 s). The results showed that the IHT caused a significant (p < 0.05) increase in retention time in the target at rest (RT9rest) by 14.4% in hypoxia, whereas RT postincremental test (RT9post) increased by 27.4% in normoxia and 26.7% in hypoxia. No significant changes in this variable were found in group C. Additionally, the capillary oxygen saturation at the end of the maximal effort (SO2capillary max) in hypoxia increased significantly (p < 0.001) by ∼4% after IHT. The maximal workload during the incremental test (WRmax) in normoxia also increased significantly (p < 0.001) by 6.3% after IHT. Furthermore, in absolute and relative values of VO2max in normoxia, there was a propensity (p < 0.07) for increasing this value by 5% in group H. In conclusion, the main findings of this study showed a significant improvement in resting and postexercise aiming performance in normoxia and hypoxia. Furthermore, the results demonstrated beneficial effects of the IHT protocol on aerobic capacity of biathletes.

Comparison of the effect of intermittent hypoxic training vs. the live high, train low strategy on aerobic capacity and sports performance in cyclists in normoxia.

The aim of the study was to compare the effect of intermittent hypoxic training (IHT) and the live high, train low strategy on aerobic capacity and sports performance in off-road cyclists in normoxia. Thirty off-road cyclists were randomized to three groups and subjected to 4-week training routines. The participants from the first experimental group were exposed to normobaric hypoxia conditions (FiO2 = 16.3%) at rest and during sleep (G-LH-TL; n=10; age: 20.5 ± 2.9 years; body height 1.81 ± 0.04 m; body mass: 69.6 ± 3.9 kg). Training in this group was performed under normoxic conditions. In the second experimental group, study participants followed an intermittent hypoxic training (IHT, three sessions per week, FiO2 = 16.3%) routine (G-IHT; n=10; age: 20.7 ± 3.1 years; body height 1.78 ± 0.05 m; body mass: 67.5 ± 5.6 kg). Exercise intensity was adjusted based on the lactate threshold (LT) load determined in hypoxia. The control group lived and trained under normoxic conditions (G-C; n=10; age: 21.8 ± 4.0 years; body height 1.78 ± 0.03 m; body mass: 68.1 ± 4.7 kg; body fat content: 8.4 ± 2.4%). The evaluations included two research series (S1, S2). Between S1 and S2, athletes from all groups followed a similar training programme for 4 weeks. In each research series a graded ergocycle test was performed in order to measure VO2max and determine the LT and a simulated 30 km individual time trial. Significant (p<0.05) improvements in VO2max, VO2LT, WRmax and WRLT were observed in the G-IHT (by 3.5%, 9.1%, 6.7% and 7.7% respectively) and G-LH-TL groups (by 4.8%, 6.7%, 5.9% and 4.8% respectively). Sports performance (TT) was also improved (p<0.01) in both groups by 3.6% in G-LH-TL and 2.5% in G-IHT. Significant changes (p<0.05) in serum EPO levels and haematological variables (increases in RBC, HGB, HCT and reticulocyte percentage) were observed only in G-LH-TL. Normobaric hypoxia has been demonstrated to be an effective ergogenic aid that can enhance the exercise capacity of cyclists in normoxia. Both LH-TL and IHT lead to improvements in aerobic capacity. The adaptations induced by both approaches are likely to be caused by different mechanisms. The evaluations included two research series (S1, S2). Between S1 and S2, athletes from all groups followed a similar training programme for 4 weeks. In each research series a graded ergocycle exercise test was performed in order to measure VO2max and determine the lactate threshold as well as a simulated 30 km individual time trial.

The Effects of Altitude Training on Erythropoietic Response and Hematological Variables in Adult Athletes: A Narrative Review.

Background: One of the goals of altitude training is to increase blood oxygen-carrying capacity in order to improve sea-level endurance performance in athletes. The elevated erythropoietin (EPO) production in hypoxia is a key factor in the achievement of enhanced hematological variables. The level of the EPO increase and acceleration of erythropoiesis depend on the duration of exposure and degree of hypoxia. Furthermore, many other factors may affect the hematological response to altitude training. Aim: The purpose of this narrative review was to: (1) analyze the kinetics of EPO and hematological variables during and after altitude training; (2) summarize the current state of knowledge about the possible causes of individual or cohort differences in EPO and hematological response to altitude training; (3) formulate practical guidelines for athletes to improve the efficiency of altitude training. Methods: A narrative review was performed following an electronic search of the databases PubMed/MEDLINE and SPORTDiscus via EBSCO for all English-language articles published between 1997 and 2017. Results: Complete unification of results from studies on EPO kinetics was difficult due to different time and frequency of blood sampling by different researchers during and after altitude training, but the data presented in the reviewed literature allowed us to detect certain trends. The results of the reviewed studies were divergent and indicated either increase or no change of hematological variables following altitude training. Factors that may affect the hematological response to altitude training include hypoxic dose, training content, training background of athletes, and/or individual variability of EPO production. Conclusions: Despite the potential benefits arising from altitude training, its effectiveness in improving hematological variables is still debatable. Further research and better understanding of factors influencing the response to altitude, as well as factors affecting the suitable measurement and interpretation of study results, are needed.