Sex-Differences in the Oxygenation Levels of Intercostal and Vastus Lateralis Muscles During Incremental Exercise

Abstract

This study aimed to examine sex differences in oxygen saturation in respiratory (SmO2-m.intercostales) and locomotor muscles (SmO2-m.vastus lateralis) while performing physical exercise. Twenty-five (12 women) healthy and physically active participants were evaluated during an incremental test with a cycle ergometer, while ventilatory variables [lung ventilation (V.E), tidal volume (Vt), and respiratory rate (RR)] were acquired through the breath-by-breath method. SmO2 was acquired using the MOXY® devices on the m.intercostales and m.vastus lateralis. A two-way ANOVA (sex × time) indicated that women showed a greater significant decrease of SmO2-m.intercostales, and men showed a greater significant decrease of SmO2-m.vastus lateralis. Additionally, women reached a higher level of ΔSmO2-m.intercostales normalized to V.E (L⋅min–1) (p < 0.001), whereas men had a higher level of ΔSmO2-m.vastus lateralis normalized to peak workload-to-weight (watts⋅kg–1, PtW) (p = 0.049), as confirmed by Student’s t-test. During an incremental physical exercise, women experienced a greater cost of breathing, reflected by greater deoxygenation of the respiratory muscles, whereas men had a higher peripheral load, indicated by greater deoxygenation of the locomotor muscles.

Determination of the Respiratory Compensation Point by Detecting Changes in Intercostal Muscles Oxygenation by Using Near-Infrared Spectroscopy

“…Few studies have focused on identifying RCP using a NIRS device on respiratory muscles during exercise. Although, Moalla et al, (2005) in children [ 24 ], Fontana et al (2015) [ 16 ] in healthy adults, and Rodrigo-Carranza et al, (2021) in runners [ 25 ] have reported interesting results, those data are difficult to extrapolate to our participants owing to factors such as the method used for RCP determination [ 11 , 32 ], sex-differences associated to ventilatory response to exercise [ 23 ], high biological variability of cardio-ventilatory responses during exercise in a non-steady-state [ 19 ], breathing patterns adopted during effort [ 21 ], intensity of physical exercise performed [ 20 , 34 , 35 , 36 ], decreased muscle perfusion as a consequence of muscular contractions [ 37 , 38 ], loss of SmO 2 signal due to changes in positions and/or adipose tissue where the devices are positioned [ 39 , 40 ], and type of device used to record muscle oxygen levels [ 12 , 30 , 41 , 42 ]. In this study, we used a MOXY ® for recording SmO 2 - m.intercostales.…”

“…The participants did not consume drugs, antioxidants, or any nutritional support. The sample size calculation was done by the software G*Power ® 3.1 (Heinrich-Heine-University, Dusseldorf, Germany) using previous data concerning the changes in oxygen saturation levels at m.intercostales from rest to respiratory compensation point (or anaerobic threshold, VT2) found in healthy subjects during cycling (from 77.5 to 64.0%) [ 23 ] and competitive marathoners during running (from 74.6 ± 10.7 to 52.9 ± 11.4%; and effect size 1.387) [ 21 ], considering a significance level of 5%, statistical power of 80% and two-tail test, plus considering 5% of data losing.…”

“…The light penetration depth is half of the distance between the emitting source and the detector (±12.5 mm) [ 30 , 31 ]. To determine SmO 2 - m.intercostales , a MOXY ® device was located in the seventh intercostal space of the anterior axillary line of the right hemithorax [ 21 , 22 , 23 ]. The device was fixed to the skin using the material suggested by the manufacturer, in addition to extra fixation with a cohesive band on the measurement zone, avoiding excessive compression that could alter the SmO 2 record (see Figure 1 ).…”

“…Considering that determination of VT is based on changes at ventilatory variables (mainly, lung ventilation ( E)), it is relevant to know if changes at SmO 2 of respiratory muscles (SmO 2 -RM) during exercise could help to determine training zones, and specifically the RCP. Our research group previously had been reported the good-to-excellent reliability of SmO 2 -RM measurements in long-distance runners [ 22 ], the impact associated with breathing patterns [ 21 ], and sex differences during exercise [ 23 ].…”

Usefulness of Portable Device to Establish Differences in Muscle Oxygenation Between the Wingate Test and Graded Exercise Test: Effect of Gender on Anaerobic and Aerobic Capacity in Speed Skaters

“…Furthermore, gender differences in SmO 2 response to test effort in athletes were also evaluated, which, to our knowledge, has not yet been described in the literature. We have found only one recent published research that attempts to assess muscle oxygenation responses in relation to gender, but unlike the current study, it involved physically active participants, not athletes ( Espinosa-Ramírez et al, 2021 ).…”