The importance of the estimation protocol alone has been discussed in previous chapters. When proper anchoring procedures are performed and it is confirmed that the individual’s perceptual responses conform to Borg’s Range Model, the estimation protocol allows the measurement of RPE from very low to maximal exercise intensity. The estimation protocol can be used to test the concurrent validity of an RPE Scale. In this type of validity experiment, RPE is correlated with such physiological variables as VO₂ and HR that increase concurrently with increasing aerobic exercise intensity.

The measurement of RPE and corresponding physiological variables during an estimation protocol allows the prescription of an exercise intensity that provides an overload training stimulus for cardiorespiratory conditioning. This prescribed exercise intensity can be based on a specific physiological marker such as the VT. The RPE-VT is then used as the target RPE for exercise prescription. Previous studies have shown RPE-VT to range from 5 to 7 on the OMNI Scale and 11 to 16 on the Borg Scale. Recently, Parfitt and colleagues (2012) guided sedentary adults through an 8-week perceptually regulated exercise program. Using an estimation–production paradigm, subjects were taught to self-regulate exercise intensity to produce an exertional level equivalent to 13 on the Borg Scale. The perceptually regulated training program resulted in significant improvements in mean arterial pressure, total cholesterol, and body mass index over the 8-week period (Parfitt et al. 2012).

An estimation protocol that employs corresponding physiological monitoring also allows the determination of an appropriate exercise intensity range to promote cardiorespiratory fitness. This range can be based on specific VO₂ or HR values corresponding to a percent of maximum level or a percent of the VT. The appropriate exercise intensity range to elicit improvement in cardiorespiratory fitness depends on the training level of the individual (Garber et al. 2011). Regular aerobic exercise at intensities between 70 and 85 % of VO₂max is an accepted range to provide an overload stimulus to enhance cardiorespiratory fitness (Robertson 2004), even in trained individuals (Midgley et al. 2006). Therefore, the RPE’s corresponding to 70 and 85 % of VO₂max can serve as an appropriate target perceptual range for exercise prescription. However, intensities as low as 30 % of VO₂ reserve may be sufficient to improve cardiorespiratory fitness in low fit individuals (Swain and Franklin 2002) and very high exercise intensities may be necessary for trained runners to improve cardiorespiratory fitness (Midgley et al. 2006). Individual aerobic fitness level must be taken into account prior to exercise intensity prescription, even when the overload stimulus is expressed in relative terms.

The production exercise protocol is administered after the estimation exercise protocol. When the individual begins exercise, he/she is asked to self-regulate exercise intensity to produce the target RPE or target RPE range that has been prescribed based on the responses to the estimation protocol. The individual is instructed to adjust exercise intensity throughout the production protocol in order to continually produce the prescribed target RPE (range). VO₂ and/or HR are monitored just as during the estimation protocol so that physiological values can be compared between trials to document validity of the self-regulation procedures. If the individual accurately self-regulated exercise intensity by producing the target RPE(s), the physiological responses from the production trial should be similar to those corresponding to the same target RPE(s) derived from the estimation trial. This is termed prescription congruence (Robertson et al. 2002). If the physiological values are different between the estimation and production protocols when measured at the prescribed target RPE, then it is said that the individual is exhibiting exercise intensity self-regulation error. The validity of exercise intensity self-regulation using a target RPE can be tested with an assessment of prescription congruence. Evidence for prescription congruence has been shown in studies of cycle ergometry, arm ergometry and treadmill exercise for children and adults (Dunbar et al. 1992, 1994; Dunbar and Kalinski 2004; Kang et al. 1998, 2003, 2009; Parfitt et al. 2007; Robertson et al. 2002), including children with cystic fibrosis (Higgins et al. 2013) and adults with cardiovascular disease (Weiser et al. 2007).

Robertson and colleagues (2002) confirmed prescription congruence in 8–12 year-old children during cycle ergometer exercise. During two separate 6-min production trials, the children were instructed to produce the target RPE’s 2 and 6 from the Children’s OMNI Cycle Scale in either ascending or descending order. Prescription congruence was exhibited for both target RPE’s using HR and VO₂. Neither the order of target RPE production nor gender had an effect on the accuracy of exercise intensity self-regulation (Robertson et al. 2002).

Weiser and colleagues (2007) presented evidence for prescription congruence for cycle ergometer exercise in cardiovascular disease patients participating in cardiac rehabilitation. During the first 6-min production trial, patients produced a target Borg Scale RPE of 13. During the second 6-min production trial, patients were instructed to begin exercise by producing an RPE of 11 then adjust intensity to produce a target RPE of 13 for minutes 3 through 6. The researchers termed this procedure an RPE “step-up” procedure, positing that it would reduce the likelihood of overshoot, or producing an intensity higher than the target. Overshoot production could be potentially hazardous in this population, putting them at risk of an untoward cardiovascular event during exercise. Prescription congruence was confirmed since HR corresponding to an RPE of 13 measured during the estimation trial was similar to HR at the end of both production trials. In addition, the RPE step-up procedure resulted in significantly less patients producing a HR that was higher than the target intensity (Weiser et al. 2007).

The aforementioned studies examined prescription congruence using a single exercise mode. Thus, the experimental paradigm involved intramodal prescription congruence, where estimation and production protocols employed the same exercise modality. For example, target RPE’s obtained from a cycle ergometer estimation protocol were used to self-regulate exercise intensity during cycle ergometer production protocols. Normally, target RPE’s are based on a predetermined %VO₂max/peak. However, VO₂max/peak varies with differing exercise modalities. As such, it is necessary to examine the validity of intermodal estimation–production paradigms to prescribe and self-regulate exercise intensity using a target RPE. It is possible that an exercise prescription could involve the production of a target RPE using multiple modes of exercise. In this instance, multiple estimation protocols should be administered employing exercise modes that match those used in the production protocols. However, this poses a problem from a practical standpoint since multiple maximal GXTs would require additional burden for both client and exercise professional. Nevertheless there is an advantage in employing multiple exercise modes in a single conditioning session. In particular, such an approach to exercise programming could improve PAE and increase participation. Therefore, some investigations have examined an assessment of prescription congruence between modes, i.e., intermodal or cross-modal prescription congruence. This paradigm involves estimation and production protocols of differing modes of exercise. For example, target RPE’s obtained from a cycle ergometer estimation protocol can be used to self-regulate exercise intensity during a treadmill exercise production protocol or vice versa. The significance of intermodal prescription congruence is the ability to require the performance of only one pre-participation GXT prior to a multimodal exercise prescription.

A study by Kang et al. (2003) tested intramodal and intermodal prescription congruence for target OMNI Scale RPE’s corresponding to 50 and 70 % VO₂max/peak in young physically active men and women. Estimation protocols and 20-min production trials were performed for both cycle ergometer and treadmill exercise. Subjects were assigned to one of four groups: estimation and production protocols on a treadmill, estimation and production protocols on a cycle, estimation protocol on a treadmill and production protocol on a cycle, estimation protocol on a cycle and production protocol on a treadmill. Intramodal prescription congruence was confirmed for treadmill and cycle ergometer exercise at 50 and 70 % VO₂max/peak using HR and VO₂ as criterion variables. At only one time-point during the treadmill exercise production protocol was HR higher than the treadmill estimation protocol for a given target RPE. However, intermodal prescription congruence was not confirmed in this paradigm. For the treadmill estimation-cycle ergometer production group, VO₂ and HR were significantly lower during the production protocol for both intensities. For the cycle ergometer estimation-treadmill production group, VO₂ and HR were significantly higher during the production protocol for both intensities (Kang et al. 2003).

The results of the Kang et al. (2003) investigation reveal a problem that can arise when using an intermodal estimation–production paradigm to prescribe exercise intensity according to a target RPE. Physiological responses (VO₂, HR) compared between treadmill and cycle ergometer exercise at the same level of exertion will be higher during treadmill exercise due to a higher metabolic rate and, subsequently, a higher HR and VO₂ (Robertson et al. 1990). Kang and colleagues (2003) conducted a post hoc comparison that normalized physiological variables measured during production protocols to mode-specific estimation trials performed by subjects in other groups. In that analysis, HR and VO₂ values were similar to 50 and 70 % VO₂max/peak as expected (Kang et al. 2003). From a practical standpoint, an estimation protocol employing a single exercise mode (i.e., treadmill or cycle) may be used to identify a target RPE to self-regulate exercise intensity during production protocols of various exercise modalities. It should be expected that physiological responses may change with the metabolic demands of different types of exercise. Regardless, a number of investigations have found evidence for intermodal prescription congruence as evidenced by similar physiological responses between estimation and production modes with assessment undertaken at the same target RPE.

Dunbar and colleagues (1992) presented evidence for intramodal and intermodal prescription congruence in 17–35-year-old men ranging from sedentary to very active. Subjects performed two estimation protocols, one on a cycle and one on a treadmill. These trials were used to calculate target RPE’s from the Borg Scale corresponding to 50 and 70 % VO₂max/peak. Subjects then performed four production protocols; two on a cycle and two on a treadmill, each involving self-regulation of exercise intensity at target RPE’s corresponding to 50 and 70 % VO₂max/peak. Each exercise bout was 8 min in duration with 5 min of rest between intensities. Both intramodal and intermodal prescription congruence was confirmed for the production trials using target RPE’s derived from the cycle ergometer estimation trial. VO₂ and HR values corresponding to 50 and 70 % VO₂peak measured during the cycle ergometer estimation trial were similar to VO₂ and HR measured during the production trials performed on both the cycle and treadmill. Intermodal prescription congruence was confirmed for the cycle ergometer production trial using target RPE’s derived from the treadmill estimation trial. However, intramodal prescription congruence for treadmill exercise was confirmed only using the target RPE corresponding to 50 % VO₂max. During the production protocol using the target RPE corresponding to 70 % VO₂max, subjects selected a lower treadmill intensity resulting in lower VO₂ and HR values (Dunbar et al. 1992).

In a similar design, Dunbar and colleagues (1994) tested intramodal and intermodal prescription congruence in active college-aged men. Following a cycle ergometer estimation protocol, four 25-min production protocols were performed at a target RPE (Borg Scale) corresponding to 60 % VO₂peak. Two production protocols were performed on a cycle ergometer to test intramodal prescription congruence and the reproducibility of cycle ergometer exercise intensity self-regulation. Two production protocols were performed on a treadmill to test intermodal prescription congruence and the reproducibility of treadmill exercise intensity self-regulation. Interestingly, intermodal prescription congruence was confirmed but intramodal prescription congruence was not. VO₂ and HR values were similar at 60 % VO₂peak during the cycle ergometer estimation trial and throughout both treadmill production protocols. VO₂ values were similar for only one of the cycle ergometer production protocols, but significantly lower for the other. HR values were significantly lower than the estimation protocol during both cycle ergometer production protocols (Dunbar et al. 1994). These results indicate a somewhat better ability of the subjects tested to self-regulate exercise intensity during treadmill exercise than cycle ergometer exercise.

Higgins and colleagues (2013) presented evidence for prescription congruence in 10–17 year-old children with cystic fibrosis during cycle ergometer and treadmill exercise. First, the subjects performed an estimation protocol on a cycle ergometer. Then, two separate 10-min production protocols were employed. The first protocol was performed on a cycle ergometer to assess intramodal prescription congruence, while the second was performed on a treadmill to assess intermodal prescription congruence. The children were instructed to self-regulate exercise intensity at target RPE’s of 4 and 7 using the Children’s OMNI Cycle RPE Scale. Both protocols were performed using an interval exercise format during which the children alternated between the target RPE’s of 4 and 7 performed for 2-min intervals. Intervals 1, 3 and 5 were performed at an RPE of 4, while intervals 2 and 4 were performed at an RPE of 7. VO₂ and HR from both the cycle ergometer and treadmill production protocols were compared to the values measured during the cycle ergometer GXT. Prescription congruence was not confirmed at an RPE of 4 during the cycle production protocol. VO₂ and HR were significantly higher during the production protocol than the estimation protocol. Prescription congruence was confirmed at an RPE of 4 during the treadmill production protocol and at an RPE of 7 for both the cycle and treadmill production protocols (Higgins et al. 2013).

The studies by Dunbar and colleagues (1992, 1994) and, more recently, Higgins et al. (2013) largely support prescription congruence, but some inconsistencies have been shown for both intramodal and intermodal perceptual prescription procedures. Prescription congruence data were also inconsistent in a study of cycle ergometry and outdoor track walking/running in overweight children (Ward and Bar-Or 1990). Therefore, additional instruction, practice, and feedback may be necessary for some individuals to accurately self-regulate exercise intensity using a target RPE, whether the estimation trial is mode-specific or not.

The physiological values corresponding to target RPE(s) should be measured during the estimation protocol prior to performance of the production protocol. These same physiological values can be monitored during the production protocol to provide feedback to the individual regarding the accuracy of exercise intensity self-regulation according to a target RPE. If the individual is accurately self-regulating exercise intensity, positive reinforcement can be given. Evidence that the individual is exhibiting exercise intensity self-regulation error by either overshooting or undershooting the target level is provided by the VO₂ and HR responses. When such self-regulation error is present, feedback can be provided that exercise intensity should be either decreased or increased to attain the desired level. This would be considered a form of teleoanticipation, whereby feedback is given during practice exercise trials prior to participation in an actual exercise program (Ulmer 1996). Providing an individual with multiple production protocols, or pre-participation practice trials, and simultaneously giving appropriate feedback regarding correction of self-regulation error may improve prescription congruence, i.e., avoid exercise intensity self-regulation error.

Dunbar and Kalinski (2004) conducted a 20-week cycle ergometer exercise training study in postmenopausal women. Target RPE’s were identified for intensities corresponding to 40, 50 and 60 % of VO₂peak during an initial pre-participation GXT. This testing protocol allowed the training intensity to be increased throughout the first 5 weeks of the exercise program. Specifically, exercise intensity was self-regulated at the target RPE corresponding to 40 % VO₂peak during the first 2 weeks, 50 % VO₂peak during weeks 3 and 4, and 60 % VO₂peak from weeks 5 through 20. Prescription congruence was tested by comparing the average HR achieved during exercise training bouts to the HR corresponding to target RPE’s achieved during the pre-participation GXT. At week 2, prescription congruence was confirmed for the target RPE corresponding to 40 % VO₂peak. At week 4, prescription congruence was not confirmed for the target RPE corresponding to 50 % VO₂peak since HR values were significantly lower than the target values. At weeks 6 and 10, HR values were again significantly lower than the target values corresponding to 60 % VO₂peak. At week 20, prescription congruence was confirmed for the target RPE corresponding to 60 % VO₂peak. These results indicate that the women in the study were able to accurately self-regulate exercise intensity at an RPE corresponding to 40 % VO₂peak, but that several weeks of practice might be necessary to accurately self-regulate exercise intensity above 40 % VO₂peak where a target RPE is employed. The researchers provided the subjects with no feedback regarding exercise intensity self-regulation, i.e., the women were not instructed to either increase or decrease exercise intensity when they were respectively under- or over-producing intensity at RPE’s corresponding to 50 and 60 % VO₂peak (Dunbar and Kalinski 2004). In this case, teleoanticipation administered during the pre-participation period may have improved the women’s accuracy in exercise intensity self-regulation at intensities above 40 % VO₂peak.

The undifferentiated perceptual rating for the overall body may not always be the best choice to prescribe a target RPE to self-regulate exercise intensity. It has been shown that an RPE differentiated to the legs (RPE-L) often provides the dominant perceptual signal during treadmill and cycle ergometer exercise. Therefore, prescribing and self-regulating exercise intensity using a target RPE-L may be preferable under some conditions. That is, choosing the comparatively more intense differentiated RPE signal for exercise intensity self-regulation can help the individual stay within functionally and perceptually tolerable limits (Robertson 2004).

Using a differentiated RPE for exercise prescription can be particularly useful when developing an exercise program for individuals with certain clinical disorders. Self-regulating exercise intensity based on RPE differentiated to the chest and breathing (RPE-C) is appropriate for those who experience exertional dyspnea, including individuals with pulmonary limitations such as (exercise-induced) asthma, chronic obstructive pulmonary disorders, or cystic fibrosis. In addition, the use of RPE-L or RPE differentiated to the arms is appropriate in the rehabilitation setting for limb-specific exercises following (neuro)muscular or articular injury (Robertson 2004).

A unique advantage of an RPE-based exercise prescription compared to traditional exercise prescriptions that are based on absolute exercise intensity and/or HR can be seen in the perceptual production protocol. A traditional HR-based exercise prescription involves determining a target HR or HR range. Similar to a target RPE, target HR’s are prescribed because they correspond to specific physiological intensities shown to provide an overload stimulus and elicit physiological benefit when performed as part of a regular exercise program. In this procedure the training intensity is set at the VT or a certain percent of maximum. If the individual is adherent to the HR-based exercise prescription, aerobic fitness level improves over time. As aerobic fitness improves, the individual becomes more metabolically efficient at any given submaximal aerobic exercise intensity. Subsequently, less cardiorespiratory work is required to perform the same exercise intensity. Some exercise prescriptions employ an absolute intensity, such as a specific power output setting on an ergometer. In the presence of a training induced increase in maximal aerobic power, the prescribed absolute intensity will no longer serve as an overload stimulus and physiological benefits will plateau. As aerobic fitness increases, changes occur in the individuals overall HR range. Resting HR decreases as parasympathetic (vagal) tone increases. The HR required to produce a specific aerobic metabolic demand may be different. In addition, HR is sensitive to environmental extremes, such as high heat and humidity, which will not cause concomitant changes in VO₂. Therefore, periodic exercise testing will be needed to reevaluate the individual’s maximal aerobic power and the HR values corresponding to the target physiological intensity to ensure the continued effectiveness of the exercise program.