AUTHOR=Espinosa-Ramírez Maximiliano , Moya-Gallardo Eduardo , Araya-Román Felipe , Riquelme-Sánchez Santiago , Rodriguez-García Guido , Reid W. Darlene , Viscor Ginés , Araneda Oscar F. , Gabrielli Luigi , Contreras-Briceño Felipe 

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

JOURNAL=Frontiers in Physiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.738063

DOI=10.3389/fphys.2021.738063

ISSN=1664-042X

ABSTRACT=<p>This study aimed to examine sex differences in oxygen saturation in respiratory (SmO<sub>2</sub>-<italic>m.intercostales</italic>) and locomotor muscles (SmO<sub>2</sub>-<italic>m.vastus lateralis</italic>) 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 (<inline-formula><mml:math id="INEQ2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover></mml:math></inline-formula>E), tidal volume (Vt), and respiratory rate (RR)] were acquired through the breath-by-breath method. SmO<sub>2</sub> was acquired using the MOXY<sup>®</sup> devices on the <italic>m.intercostales</italic> and <italic>m.vastus lateralis</italic>. A two-way ANOVA (sex × time) indicated that women showed a greater significant decrease of SmO<sub>2</sub>-<italic>m.intercostales</italic>, and men showed a greater significant decrease of SmO<sub>2</sub>-<italic>m.vastus lateralis</italic>. Additionally, women reached a higher level of ΔSmO<sub>2</sub>-<italic>m.intercostales</italic> normalized to <inline-formula><mml:math id="INEQ3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mover accent="true"><mml:mtext>V</mml:mtext><mml:mo>.</mml:mo></mml:mover></mml:math></inline-formula>E (L⋅min<sup>–1</sup>) (<italic>p</italic> &lt; 0.001), whereas men had a higher level of ΔSmO<sub>2</sub>-<italic>m.vastus lateralis</italic> normalized to peak workload-to-weight (watts⋅kg<sup>–1</sup>, PtW) (<italic>p</italic> = 0.049), as confirmed by Student’s <italic>t</italic>-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.</p>