The six-minute walk test in outpatients with obesity: Reproducibility and known group validity

Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Huddinge, Sweden.
Physiotherapy Research International 06/2008; 13(2):84-93. DOI: 10.1002/pri.398
Source: PubMed


To assess the reproducibility and validity of the six-minute walk test (6MWT) in men and women with obesity in order to facilitate evaluation of treatment outcome.
A test--retest design was used to test reproducibility and a comparative design to test known group validity. Forty-three obese outpatients (16 male), mean age 47 (21-62) years, mean body mass index (BMI) 40 (3-62)kg-m(-2) performed the 6MWT twice within one week. Intraclass correlation (ICC1.1) and measurement error (S(w)) were calculated from the mean square values derived from a one-way repeated-measures ANOVA (fixed effect model). The reproducibility was also analysed by means of coefficient of variation (CV) and the Bland Altman method including 95% limits of agreement. The variance of the distance walked was analysed by means of regressions. The known group validity of the 6MWT (distance walked and the work of walking) in obese participants was shown by comparisons with 41 lean participants (18 male), mean age 47 (24-65) years, mean BMI 22.7 kg-m(-2) (19-25).
The obese group walked 534 m (confidence interval [CI] 508-560 the first and 552 m (CI 523-580) the second walk (p < 0.001). S(w) was 25 m, CV 4.7%, ICC1.1 was 0.96. The limits of agreement were -46 m+80 m. The validity tests showed that they walked 162 m shorter (p < 0.001) and performed much heavier work (p < 0.001) than the lean group. In the obese group, BMI alone explained 38% of the variance of the distance walked.
The 6MWT showed good reproducibility and known group validity and can be recommended for evaluating walking ability in subjects with obesity. For individual evaluation, however, an improved walking distance of at least 80 m was required to make the difference clinically significant. Despite shorter walking distance the obese participants performed heavier work than the lean.

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    • "Lean tissue mass and body fat were assessed by DXA (Lunar Prodigy , General Electric, Madison WI, USA). Physical function was assessed using the 6 min walk test [17]. Quality of life was assessed using the self-report short-form 36 health survey (SF-36v2), which was scored using Health Outcomes Scoring Software. "
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    • "Directly after the first test, physical complaints or discomforts were recorded. The 6MWT has been shown to be a reliable and valid test to assess the physical fitness of obese patients (Larsson and Reynisdottir, 2008; Beriault et al., 2009). 2.5. "
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    • "Moreover, obtaining and maintaining the resources needed to perform exercise testing on a lower extremity ergometer or treadmill may not be feasible in certain settings. The six-minute walking test (6MWT), a submaximal exercise test, has previously been found to be reproducible and valid in the obese population (Larsson & Reynisdottir, 2008; Beriault et al., 2009). Another field test of potential clinical interest is the incremental shuttle walking test (ISWT), which induces to progressive increase in walking speed through the time, demonstrates a good correlation with peak oxygen uptake (VO 2 ) in certain chronic disease cohorts (Singh et al., 1992; Billings et al., 2013). "
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