Reliability and validity of the 6-min walk test in adults and seniors with intellectual disabilities

Introduction: Adults with intellectual disabilities (ID) have significantly lower rates of physical activity and fitness than adults without ID. The 6-min walk test (6MWT) is an inexpensive and simple way to test mobility and submaximal work capacity. Purpose: To evaluate the test-retest reliability and validity of the 6MWT in adults and seniors with ID and explore factors contributing to the 6MWT distance (6MWD). Methods: 46 participants with mild, moderate and severe ID levels (age = 41 +/- 11 years) performed the 6MWT three times (T1; T2; T3) to determine test-retest reliability. To test validity, peak oxygen uptake (VO2 peak) was measured using a treadmill protocol. To analyze factors contributing to the 6MWD, sex, height, fat mass % and fat free mass %, ID level, isometric leg strength and relative VO2 peak were also measured. Results: The walking distances for T1, T2 and T3 were 460.3 +/- 76.9; 489.4 +/- 81.2 and 491.4 +/- 77.9 m, respectively. The 6MWD5 between T1-T2 and T1-T3 were significantly different (p < 0.001), but T2 and T3 were not different. The intraclass correlation coefficient between T2 and T3 was 0.96 indicating high reliability. Relative VO2 peak and isometric leg strength significantly contributed to the 6MWD (R-2= 0.55). Conclusions: The 6MWT is an easy, inexpensive, reliable and valid test in adults and seniors with ID. Familiarization is necessary to obtain reliable values. Relative VO2 peak and leg strength have significant impact on the distance walked. (C) 2015 Elsevier Ltd. All rights reserved.