Verification Phase Confirms V̇O 2max in a Hot Environment in Sedentary Untrained Males

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Sports Science

Background:

• Maximal oxygen uptake (V̇O 2max) assessment is vital for evaluating cardiorespiratory fitness.
• Environmental heat significantly impacts exercise performance and physiological responses.
• The validity of V̇O 2max determination during graded exercise testing (GXT) in hot conditions requires careful consideration.

Purpose of the Study:

• To evaluate the V̇O 2 uptake from a graded exercise test (GXT) and a subsequent verification phase in untrained individuals exposed to a hot environment.
• To determine the reliability and agreement between GXT-derived V̇O 2max and verification phase V̇O 2max in the heat.

Main Methods:

• Twelve sedentary males underwent a GXT followed by a supramaximal-load verification phase in a hot environment (39°C, 32% RH).
• Rest periods between tests allowed for gastrointestinal temperature to return to baseline.
• V̇O 2max was measured during both GXT and verification phases, with individualized plateau analysis.

Main Results:

• The mean V̇O 2max from the verification phase (37.8 ± 4.3 mL·kg -1 ·min -1) was significantly lower than the GXT (39.8 ± 4.1 mL·kg -1 ·min -1).
• Only 17% of participants achieved a V̇O 2 plateau during the GXT.
• The verification phase confirmed GXT V̇O 2max in 100% of participants, showing strong correlation (r=0.86) and low bias (-2.1 ± 1.9 mL·kg -1 ·min -1).

Conclusions:

• A V̇O 2 plateau is rarely achieved during GXT in the heat for untrained males.
• The verification phase is a valuable and reliable method to confirm V̇O 2max when GXT is performed in hot conditions.
• Standard V̇O 2max criteria may underestimate achievement in hot environments, highlighting the utility of verification.