The reliability of VO2 kinetics during a 6-minute walking test is influenced by walk speed.
Daisuke Fujita, Yuusuke Kubo
PMID 34873366WHAT IT FOUND
Measuring oxygen uptake kinetics during a 6-minute walk test is more reliable when patients walk fast (6.0 km/h) than at a comfortable pace (4.5 km/h).
The fast pace produced less variability, while the slow pace had wider limits of agreement.
Key findings
01The reliability of the time constant for oxygen uptake was higher at the fast walking speed, with an intraclass correlation coefficient of 0.83 compared to 0.52 at the comfortable speed.
02The limits of agreement for the time constant were narrower at the fast speed (−3.9 to 2.1 seconds) than at the comfortable speed (−8.5 to 2.3 seconds).
03The study suggests that the initial phase of oxygen uptake response may be unstable at slower walking speeds due to the mechanics of starting on a treadmill.
STILL TO COME
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What it does not show
The study included only ten healthy young adults with no cardiovascular or respiratory diseases, so the results cannot be generalized to patients with conditions like heart failure or COPD, which are the primary populations for these tests. The sample size was very small (n=10), which limits the certainty of the reliability estimates. The study was conducted on a treadmill, whereas the standard 6-minute walk test is often performed on a flat overground course; the mechanics of starting a treadmill may differ from overground walking, potentially affecting the phase I oxygen uptake response. The authors note that the results are not recommended for application to patients with diagnosed heart or lung diseases.
Declared interests
The study received a grant from Health Science University. The authors declared no conflicts of interest.
The easy way to misread this
Do not apply these reliability findings to patients with heart or lung disease. The study only tested healthy young adults, and the authors explicitly state that the results should not be used for clinical populations without further verification.