Prediction of maximal heart rate in individuals with mental retardation

Purpose: It is well known that individuals with mental retardation (MR), es pecially those with Down syndrome (DS), have low maximal heart rates (MHR). We evaluated the ability to predict MHR in individuals with MR and DS in c omparison with persons without MR. Methods: Subjects completed a maximal ex ercise test on the treadmill with metabolic and HR measurements. Stepwise m ultiple regression was used to develop prediction equations for subjects wi th MR (N=276; 97 with DS) and without (N=296) MR, ranging in age from 9-46 yr. Results: Subjects with MR exhibited significantly lower MHR (177 vs 185 beats.min(-1)) and (V)over dotO(2peak) (33.8 vs 35.6 mL-kg(-1).min(-1)). I n subjects with MR, age was a poor predictor of MHR, Y=189 - 0.59 (age) (R= 0.30, SEE=13.8 beats.min(-1); P<0.01), but age was a better predictor for s ubjects without MR, Y=205 - 0.64 (age) (R=0.52, SEE=9.9 beats.min(-1); P<0. 01). A large sample Z test indicated that these regression coefficients wer e significantly different (P<0.01). However, adding DS to the regression im proved the prediction for subjects with MR, Y=210 - (0.56 age) - (15.5 DS) (R=0.57; SEE=11.8 beats.min(-1), P<0.01). Conclusion: MHR can be predicted with similar accuracy in subjects with and without MR, provided DS is accou nted for in the equation for the subjects with MR.