Predicting Maximal Oxygen Uptake Using the 3-Minute All-Out Test in High-Intensity Functional Training Athletes

Area of Science:

• Exercise Physiology
• Sports Science
• Biophysics

Background:

• Maximal oxygen uptake (VO2max) and critical speed (CS) are key physiological determinants of endurance performance, particularly in competitive fitness events.
• Accurate measurement of VO2max typically requires expensive and time-consuming metabolic analysis.
• Critical speed (CS) can be assessed more practically in the field using a 3-minute all-out test (3MT).

Purpose of the Study:

• To investigate the relationship between VO2max and CS in athletes participating in high-intensity functional training (HIFT).
• To develop a predictive equation for VO2max based on CS measurements in HIFT athletes.

Main Methods:

• Twenty-five HIFT athletes (27.6 ± 4.5 years) completed a 3-minute all-out test (3MT) and a graded exercise test (GXT) separated by 48 hours.
• VO2max was determined during the GXT using a square-wave supramaximal verification phase.
• CS was calculated as the average speed during the final 30 seconds of the 3MT.

Main Results:

• A strong, statistically significant positive correlation was found between relative VO2max and CS (r = 0.819, p < 0.001).
• A linear regression model incorporating sex was developed to predict VO2max: VO2max (mL/kg/min) = 8.449(CS) + 4.387(Sex [0=F, 1=M]) + 14.683.
• Observed VO2max values (47.71 ± 6.54 mL/kg/min) did not significantly differ from predicted values (47.71 ± 5.7 mL/kg/min), with a standard error of the estimate of 3.34 mL/kg/min.

Conclusions:

• The significant positive relationship between VO2max and CS supports the use of the 3MT as a practical field method for predicting maximal oxygen uptake in HIFT athletes.
• This predictive approach offers a viable alternative when direct VO2max measurement via metabolic analysis is not feasible due to cost or time constraints.