Utility of including a verification stage when VO2max testing in normobaric hypoxia

Authors

Brittany Roenker, James Madison UniversityFollow

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.

Date of Graduation

5-11-2023

Semester of Graduation

Spring

Degree Name

Master of Science (MS)

Department

Department of Kinesiology

Second Advisor

Mike J. Saunders

Third Advisor

Christopher J. Womack

Abstract

Purpose: The objective of this study was to determine the utility of including a verification stage when assessing maximum oxygen consumption (VO_2max) in normobaric hypoxia (i.e., simulated high altitude), compared to sea level. A secondary aim was to assess the efficacy of primary and secondary criteria (VO₂ plateau, RER, maximum heart rate) traditionally used to confirm the attainment of VO_2max during the graded exercise test (GXT), in both normoxia and hypoxia. Methods: Twenty male (n=15) and female (n=5) subjects completed two separate cycling VO_2max trials, each consisting of a traditional GXT and a verification stage, separated by 10 min of passive rest. Each subject completed a test in normoxia and another in hypoxia, separated by ≥ 48 h and completed in a randomly counterbalanced order. The highest VO₂ aggregate over 30 s was used as the VO_2max value from each stage and condition (normoxic GXT, normoxic verification, hypoxic GXT, and hypoxic verification). Expired air was continuously collected and analyzed with a ParvoMedics metabolic cart. Data were analyzed using a series of repeated-measures ANOVAs. Results: VO_2max was higher in normoxia compared to hypoxia (p < 0.05), with no significant differences between stages (GXT vs. verification) within each condition. However, when using a threshold “meaningful effect” of 2% (i.e., 2% higher VO₂ attained in verification vs. GXT), 12 of 20 subjects exhibited higher values during the verification stage in normoxia, whereas only 3 of 20 subjects had higher VO_2max values during the verification stage in hypoxia. Based on sensitivity and specificity calculations, primary (plateau < 150 mL/min increase in VO₂ with an increase in workload) and secondary criteria (peak HR within ± 10 bpm of age-predicted HR max and RER ≥ 1.10) were unable to verify VO_2max attainment in the GXT. Conclusion: While we did not observe a stage x condition interaction, there appeared to be a meaningful difference in the proportion of subjects that achieved substantially (> 2%) higher values during verification vs. GXT in normoxia vs. the proportion of like subjects in hypoxia. Furthermore, the primary and secondary criteria from the GXT were inadequate at confirming a true VO_2max during the GXT. Altogether, the utility of including a verification stage when VO_2max testing appears to possess more utility when testing in normoxia vs. hypoxia.