Introduction. Intermittent normobaric hypoxia (INH) training is a modality that is increasingly used both in athletes and in the general population with chronic diseases. This training seeks to improve the ability to transport oxygen to the muscles. Muscle oxygenation can be quantified using near-infrared spectrometry techniques, with sensors that measure muscle oxygen saturation (SmO₂) and are placed on the skin over the muscle to be analyzed. Objective. Analyze whether the phase of the menstrual cycle (menstruation/ovulation) influences SmO₂ measurements. Method: 16 healthy women, between 20-25 years old, recreational athletes, underwent two sessions of exposure to intermittent normobaric hypoxia. One in the central days of her menstrual phase (MP) and the other in the non-menstrual phase (NMP) on the day’s furthest from this phase within her cycle. The cycle phases and regularity were established with the “My Calendar-period tracker” APP. The order was randomly assigned. Each INH session consisted of 8 cycles of hypoxia (5 minutes) – normoxia (2 minutes). The hypoxia phases were performed with the IAltitude® altitude simulator, at a simulated altitude of 4,400m (equivalent to a FiO2 of 12%), during the tests, the electrocardiogram, heart rate and SpO₂ were monitored. The Humon Hex® device was placed in the right thigh to measure SmO_2, the initial, final and five-minute recovery values were obtained. Previously, diseases and alterations that contraindicated the performance of the tests were ruled out. A medical history, auscultation, blood pressure and electrocardiogram were taken. After checking the normality of the distributions with the Shapiro-Wilk test, the paired t test was used to compare the intra-subject data and the Pearson r test to correlate anthropometric data and SmO2. All participants signed their consent, permission was obtained from the Ethics Committee of our University and the recommendations of the Helsinki Declaration were followed. Results. The characteristics of the participants were: age: 21.4±2.1 years; height 164±4.9 cm; total weight: 58.9±1.2 Kg; Fat mass percentage: 26.8±6.6%. Mean SmO2 values in MP: Initial 61.15±10.1%; final 60.67±11.14% and recovery 61.43±13.98%. SmO2 in NMP: Initial 57.35±10.37%; final 55.32±14.21% and recovery 59.25±12.83%. On the other hand, the changes in SPO₂ were MP: Initial 99.6±0.4%; final 91.9±4.7% and recovery 99.3±1.1% and SpO₂ in NMP: initial 99.5±0.6%; final 93.4±4.5% and recovery 99.5±1%. The comparison of the initial, final and recovery values of SmO₂ of each phase shows no significant differences (p>0.5). The comparison of SmO₂ between phases also shows no significant differences: initial p=0.138; final p=0.329; recovery p=0.248. The percentage of fat mass does not correlate with the initial values of SmO₂ in any of the phases, but it does correlate with the recovery values of both phases (MP r=-0.602; p=0.038; NMP r=0.764; p=0.004) and with the final values in the NMP phase (r=-0.807; p=0.002). Conclusion. No differences were observed between the MP and NMP phases. In both phases, SmO₂ decreases after exposure to INH and in recovery slightly higher values are obtained than the initial ones.