Reproducibility, validity and predictors of six-minute walk test in overweight and obese adolescents with intellectual disability.

Abstract

To assess the reproducibility and validity of the six-minute walk test (6MWT) and predictors of the six-minute walk distance (6MWD) in adolescents with overweight or obesity and intellectual disability (ID). Sixty-one adolescents with overweight or obesity and mild-to-moderate ID (intelligent quotient [IQ] 40-70; age 14-22 years) participated in this study. To test reproducibility, 39 of the participants performed the 6MWT twice with an interval of 1 week. To test validity (n = 39), peak oxygen uptake (peak VO(2)) was measured on a bicycle ergometer. For the predictor study (n = 61), weight, height, peak VO(2) and quadriceps strength were measured, and IQ and orthopedic conditions were collected from the participants' medical records. There was no significant difference between the means of the two 6MWTs (571.3 vs. 576.5 m; p = 0.452). The intraclass correlation coefficient was 0.82, indicating good reliability. The smallest real difference was 82.6 m. 6MWD correlated significantly with relative peak VO(2) (β = 0.69) indicating validity. Relative peak VO(2), height, IQ, body mass index (BMI) and quadriceps strength are predictors of the 6MWD in this population. 6MWT is a reliable and valid test in adolescents with overweight or obesity and ID. Low IQ, overweight/obesity and low physical fitness contribute to the outcome of the 6MWT.