Exercise Intensity

Abstract

Different options are available to determine the exercise intensity in cardiac rehabilitation and phase 3 to 4 follow-up training for patients with coronary artery disease. These include determining a percentage of peak oxygen uptake, the heart rate (HR) at the ventilatory anaerobic threshold, and a percentage of peak HR, as well as calculating a training range for HR as a percentage relative to resting HR and peak HR or HR reserve. The peak HR in these methods can either be estimated or assessed during a maximal or symptom limited exercise test. Furthermore, inquiring after the Borg score during exercise and the talk test are often used for training prescription. The first methods have an objective character, whereas using Borg scores and the talk test depend on the subjective experience of the patient. Some words of caution using peak HR are in place. What is the value of the predicted HR using the formula ‘‘220jage’’ when it is considerably deviant from the assessed peak HR, and what does one do when the patient is taking $-blocking agents? This formula, described by )strand and Rodahl, was derived from cross-sectional and longitudinal observations in normal men and women, and these data indeed showed a nice decline in the measured maximal HR with increasing age. However, as often in medicine, one ignores the standard deviation from the mean or the confidence intervals, which was 50 beats/min above or below the mean. Furthermore, because these data were sampled in normal individuals aged 18 to 60 years, these data cannot simply be applied in a cardiac population. Our research center has gathered data concerning peak HR from graded maximal exercise testing on a cycle ergometer in 2,646 patients who were enrolled in cardiac rehabilitation. From this group, 1,912 patients (72%) were taking $-blocking agents. From Figure 1, 3 things can be concluded. Peak HR decreases with progressing age in a population of patients with cardiac disease after a training period of 3 months, comparable with data from Astrand and Rodahl. Secondly, this trend is similar in patients with or without $-blocking therapy, although the HR is consistently lower in all age groups in patients with $-blocking therapy. Finally, the confidence limits from the regression lines predicting peak HR (ie, T40) are substantial, which shows that peak HR is a personal characteristic and impossible to predict. Consequently, the assessed peak HR is superior to the predicted peak HR in all circumstances, and especially when prescribing the exercise intensity in terms of HR in