Senior Honors Projects, 2020-current

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 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 Kurti

Nicholas D. Luden

Abstract

Purpose: Verification phases may improve the validity of maximal oxygen uptake (VO2max) 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. VO2max from the incremental GXT (iVO2max) and VO2max from the verification stage (verVO2max) 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 (iVO2max, verVO2max) as the within-subject factors. Sensitivity and specificity were calculated for the following criteria from the iVO2max 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 iVO2max and verVO2max 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 VO2max (10s > 30s > 60s, P < 0.05). Furthermore, there was a significant (P < 0.05) stage x sampling time interaction as the difference between iVO2max and verVO2max was greater for 10s than 60s sampling times. verVO2max was considered to be higher if it exceeded iVO2max 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 VO2max 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 VO2max during an incremental test has poor sensitivity and specificity and the use of HR + RER criteria exhibits poor specificity.

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