Cross validation of the 20-m shuttle run test for children and adolescents with mental retardation

We cross validated the 20-m shuttle run test of aerobic capacity in children and adolescents with mild and moderate mental retardation (MR) using the population specific formula of Fernhall et al. (1998). Nine boys and 8 girls (age = 13.7 yr) completed a maximal treadmill protocol (measured VO(2peak)) and a 20-m shuttle run (predicted VO(2peak)). The measured peak oxygen consumption (VO(2peak)) was 39.4 ml · kg^-1 · min^-1. The relationship between measured and predicted VO(2peak) was r = .86 with an SEE of 6.2 ml · kg^-1 · min^-1. Multiple regression and Bland-Altman analyses showed that there was little bias, but the Bland-Altman analysis indicated highly variable limits of agreement (Bland and Altman 1986). Thus, the traditional approach (regression analysis) to concurrent validity revealed that the 20-m shuttle run is a valid indicator of VO(2peak) in these participants. The accuracy of prediction (Bland and Altman, 1986), however, was lower than expected in a population without MR.