Using near-infrared spectroscopy to determine maximal steady state exercise intensity.

Area of Science:

• Exercise Physiology
• Sports Science
• Biomedical Engineering

Background:

• Maximal steady state (MSS) speed is crucial for endurance performance.
• Current methods using blood lactate concentration (HLa) are invasive and not optimal.
• Noninvasive techniques are sought to accurately determine MSS intensity.

Purpose of the Study:

• To investigate near-infrared spectroscopy (NIRS) for detecting muscle oxygen saturation (StO2) breakpoints during incremental exercise.
• To assess if the StO2 breakpoint intensity can predict maximal lactate steady state (MLSS) intensity.
• To compare NIRS-based StO2 breakpoint with traditional HLa methods for MSS determination.

Main Methods:

• Sixteen endurance athletes underwent incremental exercise tests.
• Muscle oxygen saturation (StO2) and blood lactate (HLa) were measured.
• Constant speed runs were performed to establish MLSS.
• Breakpoint analysis identified changes in linearity for StO2 and HLa versus running speed.

Main Results:

• StO2 and HLa breakpoints were identified in 12 out of 16 subjects.
• Predicted MLSS speeds from StO2 breakpoint and HLa breakpoint did not significantly differ from actual MLSS speeds.
• Bland and Altman analysis showed good agreement between MLSS and StO2 breakpoint speeds (mean difference 0.14 ± 0.36).

Conclusions:

• NIRS determination of StO2 breakpoint is a noninvasive and valid method for assessing MSS intensity.
• This technique is comparable to HLa-based methods for determining exercise training intensity.
• NIRS offers a practical alternative for monitoring exercise intensity in athletes.