Reliability and Repeatability of Determining Power Associated with Maximal Metabolic Steady State Using Changes in...

Area of Science:

• Exercise Physiology
• Sports Science
• Biomedical Engineering

Background:

• Muscle oxygen saturation (%SmO2) is a key indicator of exercise intensity.
• The heavy-severe domain boundary is critical for training prescription.
• Estimating this boundary using %SmO2 requires determining the power at which %SmO2 slope becomes zero.

Purpose of the Study:

• To assess the reliability and repeatability of determining the power at a %SmO2 zero-slope.
• To validate a method for identifying the heavy-severe exercise intensity domain boundary.

Main Methods:

• Thirty endurance-trained participants completed six laboratory visits.
• Muscle oxygen saturation (%SmO2) was measured using near-infrared spectroscopy (NIRS) during cycling protocols.
• Linear regression analyzed the relationship between stage power and %SmO2 slope to predict the zero-slope power.

Main Results:

• The power at %SmO2 zero-slope showed no significant differences across visits for all participants, men, and women separately.
• Excellent reliability was demonstrated with an intraclass correlation coefficient (ICC) of 0.953.
• The standard error of measurement (SEM) was 2.6 W (1.2%), indicating high precision.

Conclusions:

• The power at the muscle maximal steady state (MMSS) can be reliably determined using the %SmO2 zero-slope method.
• Near-infrared spectroscopy (NIRS) provides a dependable tool for assessing this physiological marker.
• This method offers a valid approach for delineating exercise intensity domains in athletes.