Comparing the Respiratory Compensation Point With Muscle Oxygen Saturation in Locomotor and Non-locomotor Muscles...

Area of Science:

• Exercise Physiology
• Sports Science
• Biomedical Engineering

Background:

• The muscle deoxygenation breakpoint (Deoxy-BP) measured by near-infrared spectroscopy (NIRS) correlates with the respiratory compensation point (RCP).
• Previous studies using NIRS have explored this relationship, but not simultaneously in locomotor and non-locomotor muscles during whole-body cycling.

Purpose of the Study:

• To measure muscle oxygen saturation (SmO2) using wearable NIRS sensors in both locomotor (vastus lateralis) and non-locomotor (lateral deltoid) muscles.
• To compare the Deoxy-BPs in these muscles with the RCP during a ramp cycling exercise test to task intolerance.

Main Methods:

• Twenty-two trained cyclists underwent a ramp cycling test (30 W/min).
• Muscle oxygen saturation (SmO2) was recorded from the vastus lateralis and lateral deltoid using wearable NIRS.
• Deoxy-BPs were identified using piecewise double-linear regression, while RCP was determined from gas exchange and ventilation (VE) using the V-slope method.

Main Results:

• SmO2 profiles in both vastus lateralis and lateral deltoid showed a breakpoint response near the RCP.
• No significant differences were found between the mean RCP and the mean Deoxy-BP from either muscle group.
• However, considerable individual variability was observed in the timing and sequence of these physiological breakpoints.

Conclusions:

• Wearable NIRS can detect physiological breakpoints in both locomotor and non-locomotor muscles that align with the RCP during incremental cycling.
• Despite the overall similarity, high individual variability in breakpoint timing suggests caution when using wearable NIRS to estimate RCP in ramp tests.