Manipulating graded exercise test variables affects the validity of the lactate threshold and

Area of Science:

• Exercise Physiology
• Sports Science
• Biomedical Engineering

Background:

• Maximal oxygen uptake ($\backslash n$) and lactate threshold (LT) are key physiological markers.
• Graded exercise test (GXT) protocols and LT calculation methods can influence these measurements.
• The validity of LT and $\backslash n$ determined by different GXT durations and LT calculations needs investigation.

Purpose of the Study:

• To assess the validity of $\backslash n$ and LT derived from GXTs of varying durations.
• To compare different LT calculation methods against maximal lactate steady state (MLSS).
• To identify optimal GXT protocols and analysis techniques for accurate physiological marker determination.

Main Methods:

• Seventeen trained male cyclists performed five GXTs with stage lengths of 1, 3, 4, 7, and 10 minutes.
• Maximal lactate steady state (MLSS) was determined via 30-minute constant power bouts.
• Fourteen LT methods were applied to four GXTs (3-10 min stages), yielding 56 LT values for comparison with MLSS and $\backslash n$.

Main Results:

• $\backslash n$ values from GXTs underestimated the true $\backslash n$ by approximately 1-5 mL.kg-1.min-1.
• Many traditional LT methods lacked validity when compared to MLSS.
• A novel Modified Dmax method from a 4-minute GXT provided the most accurate MLSS estimation (MD = 1.1 W; ICC = 0.96).

Conclusions:

• GXT protocol design and data analysis significantly affect $\backslash n$ and LT determination.
• $\backslash n$ and LT cannot be reliably determined from a single GXT session, even with a verification bout.
• The Modified Dmax method shows promise for valid LT assessment in cycling.