While the HRR model does reduce the error in estimation, it still has limitations regarding its accuracy and appropriateness: • As with other exercise-intensity determination techniques, it utilizes a mathematical estimation for MHR. Note: Ideally, the Karvonen technique should be based on measured maximal heart rate to yield the most accurate results.
• There is some debate over the body position in which RHR is measured. This formula was created measuring true RHR, taken in the morning in a reclining position. RHR varies by approximately five to 10 beats when a person transitions from lying to standing, thereby altering the size of the HRR. Given the concern with some inconsistencies with clients measuring their own HR, ACE recommends measuring RHR in the body position in which the client will exercise. This may necessitate the need for two sets of training zones; one for seated/recumbent positions and another for standing activities.
KEY CONCEPT Ratings of Perceived Exertion
RPE emerged in the late 1970s and early 1980s as a subjective method of gauging exercise intensity. It has since gained wide acceptance as a method of monitoring exercise intensity. There are two versions of the RPE scale: the classical (6 to 20) scale and the more contemporary category ratio (0 to 10) scale, which was developed to remedy inconsistencies with the use of the classical RPE scale (Table 11-4) (Borg, 1998). Although fully subjective, the RPE scale (in both forms) has been shown to be capable of defining the ranges of objective exercise intensity associated with effective exercise training programs. In simple terms, a rating of “moderate” on the RPE scale is more or less equivalent to 70% of HRR, a rating of “somewhat hard” is more or less equivalent to 80% of HRR, and a rating of “hard” is more or less equivalent to 85% of HRR. Thus, for all practical purposes, RPE ratings of moderate to hard span the range of recommended exercise training
