A comparison of the lactate threshold method of exercise prescription : with percent of heart rate reserve and percent of maximal heart rate methods across three fitness levels

The purpose of this study was to compare the LT method (defined as 4 mmoles/1 blood lactate) of prescribing exercise intensity with that of %HRR and %HRmax. The % VOmax values for three fitness groups performing one VOmax test on the cycle ergometer were compared as a function of three methods of exercise prescription. A college population was recruited, ranging in age from 18-26 years, and subjects were divided into three groups (n = 8, 4 males and 4 females) according to habitual aerobic exercise performed per week over the last 6 months (low fit group exercised less than 1/2 hour, middle fit group exercised 2-3 hours, and the high fit group exercised >5 hours). It was hypothesized that there would be no difference among groups in the prescribed intensity of exercise (%VOmax) when estimated by 81% HRmax, 70% of the heart rate reserve (HRR) and 4 mmoles/1 blood lactate.

The results revealed no significant difference in the %VO₂max scores as a function of method of exercise prescription for the middle fit group only. Percent VO max scores of the low fitness group indicated significant differences among all three methods of exercise prescription. Scores of the high fitness subjects revealed a significant difference between the LT method and both of the other prescription methods, which did not differ from each other.

It was concluded that for college age individuals who habitually exercise 2-3 hours per week, it appears to make no difference when prescribing exercise using 81% HRmax, 70% HRR, or 4 mmoles/1 lactate level. It was further concluded that, for the highly fit group, prescription by the 81% HRmax or 70% HRR methods (which did not differ) would result in an intensity level below the lactate threshold. In order to prescribe exercise corresponding to the 4 mmoles/1 lactate level for this fitness group, 90% HRmax and 85% HRR would be necessary.