Muscle oxygen saturation plateau : definition and verification in different oxygen availability conditions in locomotor and non-locomotor muscles

Kowalski, Tomasz (author), Rębiś, Kinga (author), Wilk, Adrian (author), Granda, Dominika (author), Białecki, Andrzej (author), Debevec, Tadej (author), Faiss, Raphael (author)

Novel wearable near-infrared spectroscopy devices allow for a better understanding of muscle oxygenation kinetics during exercise. A muscle oxygen saturation (SmO$_2$) plateau is often applied in the scientific literature, but clear criteria for its definition remain unestablished to date. The aim of this study was to develop criteria allowing for definition of SmO$_2$ plateaus. Multiple variables associated with physiological plateaus during exercise were assessed to develop a framework for an SmO$_2$ plateau. Subsequently, the existence of an SmO$_2$ plateau during 3 min all-out cycling trials (critical oxygenation plateau) was tested in different conditions of oxygen availability (i.e., normoxia and hypoxia) in vastus lateralis and triceps brachii among 30 endurance athletes. Plateau determination methods based on a threshold of change of ±5 arbitrary units (a.u.) of SmO$_2$ and expert visual assessment showed almost perfect agreement. However, a threshold of 10 a.u. yielded high SmO$_2$ variability associated with a large number of possibly false-positive detections. Conversely, relative changes (thresholds of 5% and 10%) did not align with other methods, corresponding to low absolute changes, limiting their applicability. The inter-rater agreement between individual visual assessments exhibited a higher reliability among expert versus non-expert raters. The determination of an SmO$_2$ plateau depends on the applied methodology. Overall, a critical oxygenation plateau was observed in the vastus lateralis in both normoxia and hypoxia in >90% of cases. The results of this study allow recommendation either for the use of a threshold of change corresponding to 5 a.u. of SmO$_2$ or expert visual assessment, using 30 s segments.

• Language: English
• Keywords: sport, critical oxygenation, critical power, elite athlete, exercise, hypoxia, near-infrared spestroscopy
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FŠ - Faculty of Sport
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: Str. 464-473
• Numbering: Vol. 111, iss. 2
• PID: 20.500.12556/RUL-182511
• UDC: 796:616.12-008.44
• ISSN on article: 1469-445X
• DOI: 10.1113/EP092862
• COBISS.SI-ID: 247424259
• Publication date in RUL: 14.05.2026

Record is a part of a journal

• Title: Experimental physiology
• Shortened title: Exp. physiol.
• Publisher: Wiley
• ISSN: 1469-445X
• COBISS.SI-ID: 517708569

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: šport, kritična oksigenacija, kritična moč, vrhunski športnik, vadba, hipoksija, bližnja infrardeča spektroskopija

Projects

• Funder: Poland, Ministry of Tourism and Sport
• Project number: RPW/7830/2024