Relative Heart Rate, Heart Rate Reserve, and Vo2 During Submaximal Exercise in the Elderly

Background. The purpose of this study was to examine the relationships among relative maximal heart rate (%HRmax), maximal heart rate reserve (%HRmax reserve), and maximal oxygen uptake (%Vo2max) during submaximal exercise by elderly subjects. Methods. Vo2max and HRmax were determined on 36 women and 19 men, 60 to 80 yrs of age, by a maximal treadmill test to volitional exhaustion. On a separate day, subjects underwent a submaximal treadmill protocol consisting of three 6-min exercise stages at treadmill speeds and grades estimated to elicit 40%, 60%, and 80% of HRmax reserve. Cardiorespiratory responses were determined during mins 4–5 and 5–6 of each stage. Results. Measured exercise intensities expressed by the three methods were: %HRmax reserve = 36, 55, and 79%; %HRmax = 65, 75, and 88%; % Vo2max = 53, 69, and 88%. %HRmax was greater (p \u3c .05) than % Vo2max at 53 and 69% of Vo2max. %HRmax reserve was less (p \u3c .05) than % Vo2max for all three intensities. Slopes and intercepts for the linear regression equations relating % Vo2max with %HRmax and with %HRmax reserve differed between men and women (p \u3c .05). The regression equation relating % Vo2max and %HRmax was y = −22.8 + 1.2 (%HRmax) −13.0 (Gender) + 0.2 (%HRmax × Gender): standard error of the estimate (SEE) = 9.7% and R2 = .71. The regression equation relating % Vo2max and %HRmax reserve was y = 32.4 + 0.7 (%HRmax reserve) −10.9 (Gender) + 0.2 (%HRmax reserve × Gender): SEE = 9.8% and R2 = .70 (Gender: F = 0; M = 1). Conclusions. The data indicate that there is considerable variability among methods of expressing exercise intensity and that %HRmax more closely represents % Vo2max than does %HRmax reserve (p \u3c .05) in older adults. These results are in contrast to what has been shown with younger subjects and with American College of Sports Medicine guidelines for exercise prescription