Muscle O(2) consumption by NIRS: a theoretical model

Area of Science:

• Exercise Physiology
• Biophysics
• Muscle Metabolism

Background:

• Noninvasive muscle oxygen consumption (O2) measurement was previously limited to rest or steady isometric contractions.
• Near-infrared spectroscopy (NIRS) relied on oxyhemoglobin and deoxyhemoglobin levels.

Purpose of the Study:

• To develop a mathematical model for calculating muscle O2 consumption kinetics during ischemic, aerobic, constant-load isotonic exercises.
• To enable noninvasive assessment of muscle energetics beyond steady-state conditions.

Main Methods:

• Developed a mathematical model based on known metabolic pathways of muscle energetics.
• Applied simultaneous data fitting for exercises at varying workloads.
• Utilized Monte Carlo simulations to validate the model and optimize experimental design.

Main Results:

• The model allows calculation of O2 consumption and readjustment kinetics from exercise onset.
• Simultaneous fitting of data from different workloads improved model accuracy.
• Monte Carlo simulations identified optimal experimental protocols.

Conclusions:

• The developed mathematical model significantly advances noninvasive muscle O2 consumption measurement during dynamic exercise.
• Performing experiments at different mechanical power levels is more effective than repeating the same load.
• This approach enhances the understanding of muscle energetics and oxygen kinetics.