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

Abstract

Objectives: 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). Study design: 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 VO₂) was measured on a bicycle ergometer. For the predictor study (n = 61), weight, height, peak VO₂ and quadriceps strength were measured, and IQ and orthopedic conditions were collected from the participants’ medical records. Results: 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 VO₂ (β = 0.69) indicating validity. Relative peak VO₂, height, IQ, body mass index (BMI) and quadriceps strength are predictors of the 6MWD in this population. Conclusion: 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.

Implications for Rehabilitation

• The six-minute walk test (6MWT) with continuous verbal encouragement is a valid and reliable field test in a population of adolescents with overweight and intellectual disability (ID).

• The main variables associated with the six-minute walk distance in this specific population are relative peak oxygen uptake (VO₂), height, intelligent quotient (IQ), body mass index and quadriceps strength.

• Specific characteristics of a population with ID (low IQ, higher prevalence of overweight, lower physical fitness) are contributing largely to the outcome of the 6MWT and thereby makes this test interesting for clinical use.

Keywords::

• Cardiorespiratory fitness
• peak oxygen consumption
• reliability
• six-minute walk distance

Declaration of interest: The authors declare no conflicts of interest.