Background: The use of normobaric hypoxia can bring benefits to sports performance because it improves haematological parameters and/or physical activity tests. Our objective was to conduct a systematic review so as to analyse the methods used in hypoxia and to detect its effects on middle- and/or long-distance runners. Methods: Research was conducted using five electronic databases (PubMed, SportDiscus, Cochrane Library, Scopus and PEDro) until December 2021. The methodological quality of the included studies was assessed using the PEDro scale. Results: Having analysed 158 studies, 12 were chosen for the qualitative and quantitative synthesis. A significant improvement on time until exhaustion was detected, and oxygen saturation decreased after the intervention. There were no significant changes in the 3000-metre time trial or in the haematocrit percentage. The changes in percentage of reticulocytes, heart rate, maximal heart rate, lactate concentration and erythropoietin were heterogeneous between the different research studies. Conclusion: short exposure (less than 3 h to normobaric hypoxia significantly increases the time to exhaustion). However, longer exposure times are necessary to increase haemoglobin. Altitude and exposure time are highly heterogeneous in the included studies.

Introduction: Tolerance to breathing in conditions with a decreased oxygen ratio is subject-specific. A normobaric hypoxia tolerance test (NHTT) is performed to assess the ability of each individual, as this may be influenced by genetic or personal factors such as age or gender. The aim of this study is to test the influence of deep breathing on hypoxia tolerance time. Material and methods: A total of 45 subjects (21 parachutists and 24 students) performed two NHTTs at 5050 m altitude (iAltitude). Arterial (SatO2) and muscle (SmO2) oxygen saturation were monitored with the Humon Hex® device. The first NHTT was performed with free breathing, without any instructions; and the second NHTT was performed with wide, slow, diaphragmatic breathing. The NHTT was terminated at the end of 10 min or when a value of less than 83% was obtained. Results: The first NHTT was completed by 38.1% of parachutist and 33.3% of students while the second NHTT was completed by 85.7% and 75%, respectively. In the second NHTT, both parachutists and students had a significantly (p = 0.001) longer duration compared to the first NHTT. SmO2 and SatO2 values also increased significantly (p < 0.001) in both groups (p < 0.05). Conclusion: Performing controlled diaphragmatic breathing is successful in increasing hypoxia tolerance time and/or SatO2 values.

The military parachutists are responsible of special air operations who require certain capabilities in their physical condition, due to their intense professional career. The analysis of oxygen con-sumption (VO2) and heart rate (HR) allows the determination of aerobic (VT1) and anaerobic (VT2) thresholds and used to study the adequacy of the organism to exercise and in the analysis of sporting performance. The aim of this study was to determine the effect of tactical equipment on the stress test performance of elite parachutists. 10 parachutists parti-cipated in the study, between 22 and 36 years old with an average of 27.75 years (±4.20). Anthropometric values were determined of: weight 75.69 kg (±8.79), height 173.34 cm (±5.72) and body mass index (BMI) 25.23 (±2.98). Each one, performed 2 maximal treadmill exercise testing: one a conventional stress test (A) and another with the tactical equipment (weight 20 kg) (B). We obtained maximum oxygen consumption (Metalyzer 3B) and monitored the electrocardiogram continuously. The test started at a speed of 6km/h and a slope of 1%. The results of the two test were compared. The average value and standard deviation (SD) of different variables with equipment (B) and without it (A) and p-value were obtained: velocity (A: 14.80±3.29; B: 11.50±1.42 Km/h; p=0.073), HR (A: 182.7±58.62; B: 177.75±9.71 b/m; p=0.038), VO2 (A: 51.75±13.60; B: 54.00±30.82 ml/Kg/min; p=0.891). Al-so, the values of ventilatory thresholds: VT1 and VT2 of both tests were obtained, with sig-nificant differences. Tactical equipment causes a decrease in stress test performance with changes in VT1 and VT2.