Validity And Reliability Of Ratings Of Perceived Exertion

This section focuses on the validity of RPE to represent a given physiological strain. This method may at first seem one which should be regarded with caution. Such cautionary points will first be highlighted, but practical suggestions will be given later to help increase both the validity and reliability when teaching cardiac patients to use RPE. Interestingly, among the first authors to highlight the steps to increasing the validity of patients using RPE were Maresh and Noble (1984). They specifically focus on exercise testing and prescription in cardiac rehabilitation. Noble and Robertson (1996) refer to

Maresh and Noble's (1984) six-point process to increase validity of RPE verbatim. It will be summarised in brief as part of the practical suggestions in teaching the use of RPE, but the reader is recommended to read this landmark text.

As stated in the introduction to this section, the validity of Borg's RPE scales is based on the rationale that a given number and/or verbal descriptor on the scale represents a given relative physiological strain (%VO2max, %HRRmax, %HRmax or the lactate or anaerobic threshold) (Noble and Robertson, 1996; Borg, 1998). As illustrated in Figure 3.1 (page 51) and Table 3.1 (page 54), within the main aerobic component of an exercise session, the target RPE for cardiac patients should be 12 to 15 (somewhat hard) on the RPE scale or 3 to 4 (between moderate and strong) on the CR-10 scale. Figure 3.7 (page 78) provides data that closely correspond to these matching targets for HR, oxygen uptake, blood lactate and RPE.

Whaley, et al. (1997), however, suggest that in cardiac patients, the target RPE recommendations should be viewed with caution when compared to non-cardiac individuals; they reported a wider range of RPE scores in the cardiac patients at 60% and 80% of HRRmax. Their conclusions suggest that when exercising cardiac patients at a given point on the RPE scale, there would be less certainty that this was the desired physiological level. What this study did not report was whether the validity and reliability of RPE would improve with practice.

It has been demonstrated that an individual's ability to repeat the same intensity for a given RPE improves with practice in both healthy and clinical populations (Eston and Williams, 1988; Buckley, et al., 2000; Buckley, 2003; Buckley, et al., 2004). In many of these studies the variability of the relative inter-individual physiological strain also reduced over repeated trials. In addition to the influence of familiarity on the accuracy of RPE, other factors need to be acknowledged: the mode (production or estimation) in which RPE is used, the psychological status of the exerciser, the social milieu in which the exercise takes place, the ambient environment, the mode of exercise being performed and the effects of medication. There are other factors (age, circadian rhythms, gender and the nutritional state of blood), but those discussed in this chapter are judged to have most relevance to cardiac populations. Practical suggestions for increasing the reliability and validity of RPE will be described once all these key factors that influence RPE have been discussed.

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