Accuracy of Borg's ratings of perceived exertion in the prediction of heart rates during pregnancy

Abstract

When using Borg's 6-20 scale during pregnancy, ratings of perceived exertion (RPE) did not significantly correlate with exercise heart rates (HR) (P > 0.05). The HR predicted from RPE significantly (P < 0.05) underestimated the exercise HR in the second trimester during walking (Group 1: mean difference 16 beats min-1, n = 11), aerobics classes (Group 4: mean 15 beats min-1, n = 48) and circuit training (Group 3: mean 18 beats min-1, n = 24); and in the third trimester during cycling (Group 2: mean 16 beats min-1, n = 12) and aerobics classes (Group 5: mean 11 beats min-1, n = 29). Maximal individual HR under-estimations were large for each physical activity during pregnancy, with values up to 54 beats min-1. Consequently, exercise intensity should not be monitored solely with RPE during pregnancy. © 1992.