The efficacy of a verification stage for determining VO2max and the impact of sampling time

Author

Emily J. Kontos, James Madison UniversityFollow

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Date of Graduation

5-8-2020

ORCID

https://orcid.org/0000-0003-0495-0591

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Kinesiology

Advisor(s)

Christopher J. Womack

Stephanie P. Kurti

Nicholas D. Luden

Abstract

Purpose: Verification phases may improve the validity of maximal oxygen uptake (VO_2max) measurements during maximal graded exercise testing (GXT). It is not known whether VO₂ sampling times influence the necessity of a verification stage. Methods: 15 female and 18 male test subjects (18 – 25 y) completed a treadmill incremental GXT. Speed was increased from 3.0 mph by 0.5 mph every minute until 6.0 mph was reached. Elevation was then increased by 3% every minute until volitional fatigue. Subjects then walked for five minutes at 3.0 mph and 0% grade; after which time the verification stage began at the speed and grade corresponding with the penultimate stage and continued until volitional fatigue. VO_2max from the incremental GXT (iVO_2max) and VO_2max from the verification stage (verVO_2max) were determined using 10 s, 30 s and 60 s averages from the breath x breath measurements. A repeated measures ANOVA was performed with sampling time (10, 30 and 60s) and stage (iVO_2max, verVO_2max) as the within-subject factors. Sensitivity and specificity were calculated for the following criteria from the iVO_2max portion of the protocol: plateau (< 150 ml/min increase in VO₂ over the final 2 stages), and HR + RER (achievement of at least 90% of age-predicted maximal heart rate and RER ≥ 1.10). Results: There was no main effect for stage, suggesting no differences between iVO_2max and verVO_2max for 10s (47.9 ± 8.31 ml/kg/min vs 48.85 ± 7.97 ml/kg/min), 30s (46.94 ± 8.62 ml/kg/min vs 47.28 ± 7.97 ml/kg/min), and 60s (46.17 ± 8.62 ml/kg/min vs 46.00 ± 8.00 ml/kg/min) sampling times. There was a main effect for sampling time for VO_2max (10s > 30s > 60s, P < 0.05). Furthermore, there was a significant (P < 0.05) stage x sampling time interaction as the difference between iVO_2max and verVO_2max was greater for 10s than 60s sampling times. verVO_2max was considered to be higher if it exceeded iVO_2max by more than 2%, as suggested by Midgley et al¹⁰. This was seen in 62%, 41%, and 31% of the tests for the 10s, 30s and 60s sampling times respectively. Both sensitivity and specificity for the plateau criteria was under 45% for all sampling times. Sensitivity of using HR + RER was above 80% for all sampling times and specificity was under 30%. Conclusions: A verification stage yields a higher VO_2max in a large proportion of tests and the effectiveness of the verification stage may be more important with shorter sampling times. A plateau for determining the achievement of VO_2max during an incremental test has poor sensitivity and specificity and the use of HR + RER criteria exhibits poor specificity.

Recommended Citation

Kontos, Emily J., "The efficacy of a verification stage for determining VO2max and the impact of sampling time" (2020). Senior Honors Projects, 2020-current. 39.
https://commons.lib.jmu.edu/honors202029/39