Reference Values for 6-Minute Walk Test and Hand-Grip Strength in Healthy Hong Kong Chinese Adults

This study aimed to establish reference values for the 6-minute walk test (6MWT) and hand-grip strength (HGS) in healthy Hong Kong Chinese adults and to examine their test-retest reliability. There were 548 subjects in five age strata between 21 and 70 years old. The 6MWT was administered and isometric HGS was measured following standard protocols on two occasions separated by 3 days. The 6-minute walk distance (6MWD) was measured once on each day. HGS was measured three successive times for both the dominant and non-dominant hands on each occasion. Both the mean values (mean method) and the maximum values (maximum method) of the three successive measurements were recorded for data analysis. Test-retest reliability was calculated in terms of intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimum detectable change (MDC) and 95% limits of agreement (LoA). In the first test, mean ± standard deviation (SD) of 6MWD for males and females were 635 ± 97 m and 573 ± 91 m, respectively; mean ± SD HGS (mean values) for dominant and non-dominant hands were 43.8 ± 8.0 kgf and 40.8 ± 7.8 kgf for males, and 28.5 ± 5.7 kgf and 26.2 ± 5.5 kgf for females, respectively, while mean ± SD HGS (maximum values) were 45.5 ± 8.1 kgf and 42.6 ± 8.1 kgf for males, and 29.8 ± 5.8 kgf and 27.6 ± 5.6 kgf for females, respectively. There was a mean increase of 10.8 ± 50.0 m in 6MWD in the second test. The test-retest reliabilities of 6MWD were satisfactory (ICC[2,1], 0.87; 95% confidence interval, CI, 0.84-0.89; SEM, 35.3 m; MDC, 97.8 m; 95% LoA, −87.9 to 108.6 m). The lower limit of the 95% CI for the ICC of HGS measurements was 0.94. The SEM and MDC for HGS measurements ranged from 2.0-2.2 kgf and from 5.5-6.2 kgf, respectively. The 95% LoA ranged from −6.7-5.6 kgf. This study established a set of reference values for the 6MWT and HGS in a group of healthy Hong Kong Chinese subjects. Although the test-retest reliabilities in terms of ICC for 6MWT and HGS measurement were satisfactory to high, the associated random variations were large on repeated measurements. Physiotherapists should be aware of these random errors in the evaluation of change in 6MWT and HGS. In the future, the normative values for 6MWT and HGS in Hong Kong Chinese adults should be established with random sampling of subjects from the community.