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

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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 ((Formula presented.) 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 (Formula presented.) 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.

Original languageEnglish
Article number738063
JournalFrontiers in Physiology
StatePublished - 1 Oct 2021

Bibliographical note

Funding Information:
We would like to thank all the participants, and Mr. Francisco Cerda, Mr. Gonzalo Hevia, Mr. Miguel Carrasco, and Mr. Diego Llambias for technical support in the measurements done at Laboratory of Exercise Physiology from Pontificia Universidad Cato?lica de Chile.

Publisher Copyright:
© Copyright © 2021 Espinosa-Ramírez, Moya-Gallardo, Araya-Román, Riquelme-Sánchez, Rodriguez-García, Reid, Viscor, Araneda, Gabrielli and Contreras-Briceño.


  • cost of breathing
  • exercise
  • near-infrared spectroscopy
  • respiratory muscles
  • sex


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