The age-predicted maximal heart rate (PMHR) formula, 220-age, is accepted as a useful method to prescribe exercise training intensity. However, a new equation was developed and reported by Tanaka (208-[0.7* age]) that reportedly improves prediction accuracy in individuals over 60 years of age. Whether the “new” PMHR formula also improves accuracy in unfit, obese adults has not been evaluated. Enhancing peak HR prediction is desirable to optimize exercise intensity guidelines.
To compare the 220-age PMHR formula (“PMHROLD”) with the (208-[0.7* age]) formula (“PMHRNEW”) as a method for prescribing target heart rates in sedentary, obese adults.
Sixty-six sedentary, obese adults (14 male/52 female, 41 ± 10 years, BMI 37 ± 5 kg/m2) performed a symptom-limited maximal exercise test where peak heart rate (HRPEAKactual) was determined using ECG and compared to PMHROLD and PMHRNEW (ANOVA). In addition, subjects performed a one-mile treadmill walk test at the fastest comfortable speed that could be maintained for one mile. The average heart rate determined by ECG during the last two minutes of the mile walk was measured and the corresponding intensity was determined as percentage of the actual peak heart rate (%HRPEAKactual), %PMHROLD and %PMHRNEW.
aHRPEAK(actual) < PMHROLD = PMHRNEW;*p < 0.005bHRPEAK(actual) > PMHROLD = PMHRNEW; *p < 0.005 These data show that both the old and new PMHR formula overestimated peak heart rate to a similar degree, and that the % peak HR during walking is actually higher than when obtained using either PMHR formula.
These findings suggest prescribing THR in obese adults using PMHR should be done cautiously as not to overestimate exercise training intensity.