Introduction: Near infrared spectroscopy (NIRS) is a non-invasive technique that is used in the assessment of tissue oxygenation and the monitoring of physical activity. Objective: To determine the influence of sexual, anthropometric and ergospirometric factors on muscle oxygenation of the quadriceps and gastrocnemius, obtained by NIRS during a stress test. Methods: Twenty healthy subjects participated in this study (10 women). Two Humon Hex® devices were placed on the dominant side of the quadriceps and gastrocnemius muscles to measure muscle oxygen saturation (SmO2). The stress test was performed on a treadmill with electrocardiographic control and measurement of oxygen consumption. SmO2 was obtained at rest and after maximum effort during the stress test. In addition, the height, weight, skinfold and waist contour were measured. Bioimpedance was used to obtain the percentages of fat mass and muscle mass, which were used to calculate the relative fat mass (RFM). Results: The SmO2 of both muscles at rest is higher in males than in females. At maximum effort, the SmO2 of the quadriceps is similar in both groups. The SmO2 of both muscles is positively related to height, body mass, percentage of mass muscle and waist contour, and negatively with percentage of mass fat, RFM and skinfold thickness. The negative correlation between fat percentage and oxygen saturation is more evident in females. It was observed that the variables that quantify maximum effort are not related to the SmO2 values, except for the correlation between HR max and SmO2 of the gastrocnemius muscle in males. Conclusion: The SmO2 of recreational athletes is influenced by the location of the device and the fat mass of the subjects. The biggest differences between the sexes are in the gastrocnemius muscle. Level of Evidence II; Diagnostic Studies - Investigating a Diagnostic Test .

Background: The autonomic nervous system, which is composed of the sympathetic and parasympathetic nervous system, is closely related to the cardiovascular system. The temporal variation between each of the intervals between the consecutive “R” waves of an electrocardiogram is known as heart rate variability. Depending on the type of activity, both systems can be activated, and also influence the interval between “R” waves. Currently, with advancements in technology and electronic devices, photoplethysmography is used. Photoplethysmography detects changes in the intensity of reflected light that allow differentiation between systole and diastole and, therefore, determines the heart rate, its frequency and its variations. In this way, changes in the autonomic nervous system can be detected by devices such as the Max Pulse^®. Objective: To determine whether the information provided by Max Pulse^® on autonomic balance and stress is modified after intense physical exercise, thereby determining whether there is a relationship with body composition, and also whether there are differences with respect to gender. Materials and Methods: Fifty-three runners (38.9% female) with a mean age of 31.3 ± 8.1 years participated in the study. Two measurements (before and after intense physical effort) were performed with the Max Pulse^® device. The flotoplethysmography measurement lasted 3 min, and was performed in the supine position. The exercise test was performed on a treadmill. It was initiated at a speed of 6 and 7 km/h for women and men, respectively. Subjects indicated the end of the test by making a hand gesture when unable to continue the test. Results: Autonomic nervous system activity and mental stress values decreased significantly (p < 0.05) in men and women, while autonomic nervous system balance decreased only in women. Physical stress increased (p < 0.05) in both sexes. Conclusions: Intense exercise causes changes in variables that assess autonomic nervous system balance and stress, as measured by a device based on photoplethysmography. The changes are evident in both sexes, and are not related to body composition.

The aim of this work was to analyze the influence of acute normobaric hypoxia on quadricep oxygenation. Muscle oxygen saturation (SmO₂) was measured using near-infrared spectrometry (NIRS) technology during a normobaric hypoxia tolerance test (NHTT). SmO₂ was measured with a Humon Hex^® device. In total, 54 healthy subjects participated, 68.5 of which were males and 31.5% of which were females. They performed an NHTT with the IAltitude^® simulator, breathing air with an FiO₂ level of 11% (equivalent to 5050 m). The maximum duration of the NHTT was set at 10 min, stopping if it reached 83% SpO₂. The initial values (PRE) were compared with those obtained at the end of the test (POST) and after 10 min of recovery. The participants were divided into two groups based on whether (G1) they completed the ten minutes or not (G2). In total, 35.1% of men and 41.2% of women completed the 10 min. In both groups, significant differences were observed in the decrease in SmO₂ values (p < 0.0001) (G1: PRE = 59.5 ± 12.48%; POST = 55.95 ± 14.30%; G2: PRE = 60.06 ± 13.46%; POST = 57.2 ± 12.3%). There were no differences between groups in any of the three periods. Exposure to normobaric hypoxia produces a decrease in quadricep levels of SmO₂ in both sexes, regardless of whether the test is completed. Two patterns appeared: A.—less time and more hypoxia; B. a longer duration and less hypoxia.

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 consumption (VO 2) 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 participated 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), VO 2 (A: 51.75±13.60; B: 54.00±30.82 ml/Kg/min; p=0.891). Also, the values of ventilatory thresholds: VT1 and VT2 of both tests were obtained, with significant differences. Tactical equipment causes a decrease in stress test performance with changes in VT1 and VT2.