CROSS-VALIDATION OF THE 1-MILE WALKING TEST FOR MEN WITH MENTAL-RETARDATION

The purpose of this study was to cross validate the equation developed by Rintala et al. (1992) to estimate the cardiorespiratory efficiency of men with mental retardation (MR). Subjects were 19 healthy men (27 +/- 8 yr) with MR (IQ = 58 +/- 12). Following familiarization, a grad ed maximal treadmill test and two 1-mile walk tests (Rockport Fitness Walking Test, RFWT) were administered. The peak VO2 value was the crit erion measure used to cross validate the equation. The equation was: P eak VO2, (ml . kg(-1). min(-1)) = 101.92 - 2.356 (MILE) 0.420 (WEIGHT) . The mean differences were 2.04 (MILE(1))(P = 0.02) and 2.43 (MILE(2) )(P = 0.004) ml . kg(-1). min(-1). A significant positive correlation was found between measured peak VO2 and predicted peak VO2 on both 1-m ile walks (r = 0.91 and 0.93). For both predicted peak VO2 values, the Total Error (TE) was greater than standard error of estimate (SEE), i ndicating it systematic difference between the measured and predicted peak VO2 values. Moreover, only 58% of the measured peak VO2 values fe ll within the prespecified range. Test-retest reliability of RFWT was R = 0.96. However, the prediction equation underestimated the actual c ardiorespiratory levels in 74% and 79% of the subjects, depending on t he trial. Because the equation developed in this research underestimat es the measured VO2 values for the majority of these subjects, the tes t is probably not statistically valid, even if reliable, and the predi ction formula needs to be revised for this population.