Reliability of NIRS portable device for measuring intercostal muscles oxygenation during exercise

ABSTRACT

This study assessed the intra-individual reliability of oxygen saturation in intercostal muscles (SmO₂-m.intercostales) during an incremental maximal treadmill exercise by using portable NIRS devices in a test-retest study. Fifteen marathon runners (age, 24.9 ± 2.0 years; body mass index, 21.6 ± 2.3 kg·m⁻²; V̇O₂-peak, 63.7 ± 5.9 mL·kg⁻¹·min⁻¹) were tested on two separate days, with a 7-day interval between the two measurements. Oxygen consumption (V̇O₂) was assessed using the breath-by-breath method during the V̇O₂-test, while SmO₂ was determined using a portable commercial device, based in the near-infrared spectroscopy (NIRS) principle. The minute ventilation (VE), respiratory rate (RR), and tidal volume (Vt) were also monitored during the cardiopulmonary exercise test. For the SmO₂-m.intercostales, the intraclass correlation coefficient (ICC) at rest, first (VT1) and second ventilatory (VT2) thresholds, and maximal stages were 0.90, 0.84, 0.92, and 0.93, respectively; the confidence intervals ranged from −10.8% – +9.5% to −15.3% – +12.5%. The reliability was good at low intensity (rest and VT1) and excellent at high intensity (VT2 and max). The Spearman correlation test revealed (p ≤ 0.001) an inverse association of SmO₂-m.intercostales with V̇O₂ (ρ = −0.64), VE (ρ = −0.73), RR (ρ = −0.70), and Vt (ρ = −0.63). The relationship with the ventilatory variables showed that increased breathing effort during exercise could be registered adequately using a NIRS portable device.

KEYWORDS:

• Muscle oxygenation
• exercise
• respiration
• near-infrared spectroscopy

Acknowledgments

This study received financial support for editing and translating to the English language from Pontificia Universidad Católica de Chile.

Author Contribution Statement

FCB: protocol design, data analysis, manuscript redaction, final approval.

MER: measurements, data base management.

GH, DLl, MC, FC: protocol design, data analysis.

PG, ALF: data analysis, final approval.

LG: manuscript redaction, final approval.

GV: data analysis, manuscript redaction, final approval.

Disclosure statement

No potential conflict of interest was reported by the authors.