Objective: For the purpose of prescribing exercise intensity, the American College of Sports Medicine (ACSM) provides guidelines for relating the perceived level of exertion and the heart rate (HR) response during exercise, expressed either as a percentage of maximal HR or of HR reserve, to a percentage of maximal aerobic power (VO2max). However, because maximal HR and VO2max decline with age, it is possible that these guidelines are not appropriate for an older population. The purpose of this study was to evaluate in 60- to 72-year-old women the relationships among the common methods of prescribing exercise intensity.
Design: Participants were 112 healthy but sedentary women, aged 66 +/- 4 years, who performed treadmill walking at four speeds.
Setting: Subjects were recruited from the community, and exercise tests were performed at a university laboratory facility.
Measurements: VO2max and maximal HR were determined during treadmill walking. The HR and VO2 responses to walking 6 minutes at each of four speeds ranging from 67 to 107 m/min, along with ratings of perceived exertion (RPE) and plasma lactate levels, were determined on a separate day.
Results: The exercise bouts required an average of 55 +/- 10%, 64 +/- 12%, 77 +/- 12%, and 91 +/- 9% of VO2max. Corresponding HR values were 64 +/- 8%, 70 +/- 9%, 81 +/- 10%, and 92 +/- 7% of maximal HR, and they were within the expected ranges based on ACSM guidelines. HR values as a percentage of HR reserve were much lower than expected based on the guidelines. RPE values were lower than expected at a given %VO2max, and plasma lactate levels were also relatively low, suggesting that older women are able to exercise at a higher percentage of VO2max than levels currently recommended.
Conclusions: The results indicate that HR expressed as a percentage of maximal HR is an appropriate method of prescribing exercise intensity in healthy, sedentary 60- to 72-year-old women. The HR reserve method is not recommended in this population because it will likely result in the exercise being performed at a higher than expected percentage of VO2max.