Estimating the Lactate Threshold Using Wireless Near-Infrared Spectroscopy and Threshold Detection Analyses.

Area of Science:

• Exercise Physiology
• Biomedical Engineering
• Sports Science

Background:

• Near-infrared spectroscopy (NIRS) is a non-invasive tool used to estimate physiological thresholds during exercise.
• The lactate threshold (LT) is a key indicator of endurance performance and exercise intensity.
• Threshold detection analyses like Dmax and mDmax are employed to identify NIRS-derived thresholds.

Purpose of the Study:

• To evaluate the ability of Dmax and mDmax analyses to identify NIRS thresholds as estimates of LT.
• To assess the test-retest reliability of exercising tissue oxygen saturation (StO2) and total hemoglobin concentration (THC) responses.

Main Methods:

• Fourteen healthy participants underwent maximal incremental cycling tests on two occasions.
• NIRS was used to monitor vastus lateralis StO2 and THC responses.
• Blood lactate was collected, and LT was determined alongside NIRS thresholds (NIRS1, NIRS2) using Dmax and mDmax methods.

Main Results:

• A moderate correlation was found between LT and NIRS1 using Dmax (r = 0.690), but not mDmax (r = 0.487).
• Neither Dmax (ICC = 0.351) nor mDmax (ICC = 0.385) showed significant test-retest reliability for NIRS thresholds.
• Exercising StO2 (ICC = 0.841-0.873) and THC (ICC = 0.720-0.873) demonstrated good reliability.

Conclusions:

• Dmax and mDmax analyses are not recommended for estimating LT from NIRS data due to unreliable NIRS threshold detection.
• While NIRS-derived thresholds lack reliability, the underlying StO2 and THC measurements show acceptable reliability for exercise monitoring.