ABSTRACT
PURPOSE: This study aimed to evaluate the validity and reliability of a verification test to confirm GXT VËO2max 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 VËO2max (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 VËO2max 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 VËO2max 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 VËO2max 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.