Respiratory muscle oxygenation kinetics: relationships with breathing pattern during exercise

Area of Science:

• Exercise Physiology
• Respiratory Physiology
• Sports Science

Background:

• Accessory respiratory muscles play a role in breathing during exertion.
• Understanding oxygenation kinetics in these muscles is crucial for exercise performance.
• Near-infrared spectroscopy (NIRS) allows non-invasive monitoring of muscle oxygenation.

Purpose of the Study:

• To investigate accessory respiratory muscle oxygenation (RMO2) during incremental exercise using NIRS.
• To examine the relationship between RMO2 kinetics and breathing pattern parameters.
• To identify the exercise intensity at which RMO2 breakdown occurs.

Main Methods:

• Nineteen young males underwent a maximal incremental cycle ergometer test.
• Muscle oxygenation of the serratus anterior was monitored using NIRS.
• Breathing pattern parameters (frequency, tidal volume) and ventilatory thresholds (VT1, VT2) were analyzed.

Main Results:

• All subjects exhibited decreased RMO2 (deoxygenation) during exercise.
• A breakdown in RMO2 (B-RMO2) was observed at submaximal workloads (around 86% VO2max).
• The intensity of B-RMO2 correlated significantly with breathing pattern changes (fRacc, VTplateau, VE/VT inflection) and VT2.

Conclusions:

• RMO2 breakdown appears linked to altered breathing patterns, particularly increased breathing frequency at VT2.
• Higher maximal oxygen consumption (VO2max) was associated with greater RMO2 decrease during exercise.
• These findings highlight the interplay between respiratory muscle oxygenation and ventilatory control during exercise.