Using a Portable Near-infrared Spectroscopy Device to Estimate The Second Ventilatory Threshold

Area of Science:

• Exercise Physiology
• Sports Science
• Biomedical Engineering

Background:

• The second ventilatory threshold (VT2) is a key indicator of exercise intensity.
• Near-infrared spectroscopy (NIRS) measures muscle oxygenation, potentially identifying physiological thresholds.
• Previous research linked NIRS-derived deoxygenated hemoglobin breakpoints to VT2 in healthy individuals.

Purpose of the Study:

• To investigate the association between the NIRS-derived oxygen saturation (StO2) breakpoint and VT2 in well-trained runners.
• To validate the use of portable NIRS devices for determining exercise intensity thresholds in a running context.

Main Methods:

• Ten well-trained runners underwent an incremental VO2max running test.
• Gas exchange and portable NIRS data (measuring StO2) were collected simultaneously.
• The StO2 breakpoint and VT2 were identified and compared based on %VO2max, speed, VO2, and %HRmax.

Main Results:

• No significant differences were found between the StO2 breakpoint and VT2 across measured parameters (%VO2max, speed, VO2, %HRmax).
• Strong, significant correlations (r=0.68 to 0.86, p<0.05) were observed between NIRS and gas exchange measures.
• Bland and Altman analysis showed good agreement between the NIRS breakpoint and VT2.

Conclusions:

• A portable NIRS device's StO2 breakpoint is a valid and comparable measure to VT2 determined by gas exchange in runners.
• Portable NIRS is suitable for identifying exercise training intensities above VT2 in running.
• This study provides the first validation of portable NIRS for threshold determination in running.