Verification Testing to Confirm V˙O2max in a Hot Environment

Abstract

Verification tests to confirm graded exercise test (GXT) V˙O_2max are growing in popularity, but the validity and reliability of such testing in the heat remains unknown. Purpose This study aimed to evaluate the validity and reliability of a verification test to confirm GXT V˙O_2max in a hot environment. Methods Twelve recreationally trained cyclists completed a two-test protocol that included a GXT progressing 20 W·min⁻¹ followed by a biphasic supramaximal-load verification test (1 min at 60% increasing to 110% maximal GXT wattage until failure) in a hot environment (39°C, 32% relative humidity). Rest between tests occurred in a thermoneutral room and was anchored to the duration required for gastrointestinal temperature to return to baseline. Results Mean verification test V˙O_2max (51.3 ± 8.8 mL·kg⁻¹·min⁻¹) was lower than GXT (55.9 ± 7.6 mL·kg⁻¹·min⁻¹, P = 0.02). Verification tests confirmed GXT V˙O_2max in 92% of participants using individual analysis thresholds. Bland–Altman analysis revealed a sizable mean bias (−4.6 ± 4.9 mL·kg⁻¹·min⁻¹) with wide 95% limits of agreement (−14.0 to 5.0 mL·kg⁻¹·min⁻¹) across a range of V˙O_2max values. The high coefficient of variation (9.6%) and typical error (±3.48 mL·kg⁻¹·min⁻¹) indicate potential issues of test–retest reliability in the heat. Conclusions Verification testing in a hot condition confirmed GXT V˙O_2max in virtually all participants, indicating robust utility. To enhance test–retest reliability in this environment, protocol recommendations for work rate and recovery between tests are provided.