Background Health-enhancing physical activity increasingly takes place outside the health care system and calls for self-monitored feedback tests to retain motivation. The Fox-walk test is a new method used to estimate aerobic capacity outside a clinical environment, which may be useful in the implementation of daily health-enhancing physical activity. Its measurement properties have been established in different populations, but not yet among people with rheumatoid arthritis (RA).
Objectives The purpose of this study was to determine the test-retest reliability of the Fox-walk test in patients with RA and to study potential influence on reliability of disease-related factors.
Methods Fifteen participants (14 women, mean age 63 years, mean time since first clinical visit 3.5 years) with RA according to ACR 1987 criteria performed the Fox-walk test three times with weekly intervals. A sample size calculation (α =0.05, β =0.80) indicated that 10 subjects would be enough to demonstrate a reliability of >0.8 when repeating the measurements three times. The intraclass correlation coefficient (ICC), the standard error of measurement (SEM) and the smallest detectable change (SDC) were used to estimate the reliability. General health perception, lower limb pain and fatigue were measured to determine their potential influence on the reliability.
Results There were no systematic differences between the three test occasions (p=0.190) and the reliability was almost perfect (ICC =0.982). None of the covariates influenced the reliability. The SEM was 0.999 ml/kg/min or 3.4% and the SDC was 2.769 ml/kg/min or 9.4%.
Conclusions Our findings demonstrate that the Fox-walk test is reliable in people with RA and enables differentiation between people with RA aas well as monitoring progress. The validity of the test among people with RA is however still to be determined.
Disclosure of Interest None Declared
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