The estimation–production paradigm is used to assess the validity of self-regulating exercise intensity using a prescribed target RPE. First, the target RPE and associated physiological responses are derived from the estimation test protocol. The production protocol is then presented, allowing an assessment of an individual’s ability to accurately self-regulate exercise intensity at a specific target RPE or within a specific target RPE range. Evidence that the individual can accurately self-regulate exercise intensity is obtained by comparing the physiological responses (e.g., VO₂, HR) determined during the production trial to those corresponding to the target RPE(s) determined during the estimation trial. If the physiological responses are the same between the estimation and production trials, it can be concluded that the exercise intensity prescribed using a target RPE is valid. Such a response established prescription congruence. In contrast, if the physiological responses differ between estimation and production test protocols, then the individual is exhibiting exercise intensity self-regulation error.

The validity of exercise intensity self-regulation can be tested one step further by asking the subject to produce multiple target RPE’s during single or multiple production trials. This is a method to evaluate the validity of intensity discrimination during interval exercise. In this instance, the test protocol determines the ability to perceptually differentiate between separate target RPE’s such that physiological responses differ between different self-regulated intensities (Robertson et al. 2002). Intensity discrimination during interval exercise can be tested using two different formats. The first format uses a separate production trial for each target RPE, similar to the laboratory procedures in the previous chapter. The second format requires the subject to self-regulate exercise intensities corresponding to multiple target RPE’s in the same production trial using an interval exercise protocol.

Using separate production trials for different target RPE’s, intensity discrimination has been confirmed in children during cycle ergometer exercise (Robertson et al. 2002) and adults during cycle ergometer (Weiser et al. 2007), treadmill and field running exercise (Ceci and Hassmen 1991). Robertson and colleagues (2002) confirmed exercise intensity discrimination between OMNI RPE’s 2 and 6 in children performing cycle ergometry. Weiser et al. (2007) confirmed intensity discrimination between Borg RPE’s 11 and 13 for cycle ergometer exercise in adults participating in a cardiac rehabilitation program. Ceci and Hassmen (1991) confirmed intensity discrimination between Borg RPE’s 11, 13, and 15 for both treadmill and running on an outdoor track in active adult males. Intensity discrimination data were inconsistent in a study of overweight youth performing cycle ergometry and outdoor track walking/running (Ward and Bar-Or 1990). Intensity discrimination was confirmed during cycle ergometry but not for walking/running exercise, indicating that additional instruction and practice may be necessary for overweight children and adolescents when self-regulating exercise intensity using multiple target RPE’s (Ward and Bar-Or 1990).

When performing an interval exercise protocol, the individual is instructed to begin the exercise trial by self-regulating intensity to produce a specific target RPE. After self-regulating intensity for a specified time interval, the individual is instructed to adjust the exercise intensity to produce a different target RPE for another time interval. The length and number of intervals can be adjusted to accommodate the desired amount of time to complete the entire exercise bout. A simple study of intensity discrimination could involve only one interval at each target RPE. However, multiple intervals at each target RPE are more appropriate when examining the ability of an individual to self-regulate exercise intensity. This is especially important when preparing an individual prior to performing of an interval exercise program. Additional practice, feedback, and reinforcement may be necessary when teaching an individual to perform RPE-based interval exercise compared to continuous exercise.

Higgins and colleagues (2013) used the interval production format to examine intensity discrimination and prescription congruence for both cycle ergometer and treadmill exercise. The intent of the paradigm was to assess the validity of interval exercise intensity self-regulation in children with cystic fibrosis. The research design included an estimation trial on a cycle ergometer and two interval production trials, one on a cycle ergometer and another on a treadmill. Each interval production trial simulated an actual aerobic exercise trial that could be performed during an interval exercise program. Subjects alternated between 3-min intervals of self-regulated exercise intensity at OMNI RPE’s 4 and 7 without rest between intervals. Intensity discrimination was confirmed between OMNI RPE’s 4 and 7 for cycle ergometer and treadmill exercise when both HR and VO₂ were compared between the two target RPE’s (Higgins et al. 2013). In addition, both intramodal and intermodal prescription congruence was confirmed for both RPE’s, indicating the validity of exercise intensity self-regulation during interval exercise.

For healthy adult subjects (Daussin et al. 2007; Esfandiari et al. 2014; Helgerud et al. 2007; Matsuo et al. 2013), patients with coronary artery disease and heart failure (Fu et al. 2011; Guirard et al. 2012; Haykowski et al. 2013; Rognmo et al. 2004; Wisloff et al. 2007), as well as type 2 diabetics (Mitranum et al. 2013), aerobic interval exercise has resulted in more positive health-fitness and performance-related outcomes when compared with a continuous moderate intensity program. Improvement in the rate-limiting physiological factors that influence VO₂max as well as VO₂max itself has been shown to be greater following interval training when compared to moderate intensity continuous exercise. In a study by Daussin and colleagues (2007), previously sedentary subjects performed 8 weeks each of aerobic interval exercise and continuous moderate-intensity exercise with programs presented in random order and separated by 12 weeks of detraining. These cycle ergometer exercise programs were matched for energy expenditure and exercise duration. Both programs resulted in improved arterial-venous oxygen difference, but only the interval exercise program resulted in improved VO₂max and maximal cardiac output (Daussin et al. 2007). In a study by Esfandiari and colleagues (2014), previously untrained but healthy men increased plasma volume, end-diastolic volume, stroke volume and cardiac output after only 6 sessions of cycle ergometer exercise involving either high-intensity intervals or continuous moderate-intensity training. However, only the interval exercise group significantly improved VO₂max (Esfandiari et al. 2014). In a study of previously sedentary men performing an 8-week cycle ergometer exercise program, Matsuo and colleagues (2013) found that interval training resulted in a greater improvement in VO₂max compared to continuous aerobic training. In addition, interval training resulted in significant improvements in left ventricular mass, stroke volume and resting HR as compared to continuous exercise training (Matsuo et al. 2013). Helgerud and colleagues (2007) conducted a study in which moderately trained men performed one of four, 8-week treadmill exercise programs. The protocol employed two different continuous exercise intensities (70 or 85 % of VO₂max) and two different interval exercise protocols (15-s intervals with 15-s recovery periods or 4-min intervals with 4-min recovery periods). All training programs significantly improved running economy and velocity at the lactate threshold, but only the interval exercise programs significantly improved maximal stroke volume and VO₂max. Interestingly, both the interval durations of 15 s and 4 min were equally effective (Helgerud et al. 2007).

A recent meta-analysis investigated the effect of aerobic interval training compared with moderate-intensity continuous exercise on VO₂peak and left ventricular ejection fraction in heart failure patients (Haykowski et al. 2013). Seven randomized trials were identified. Collectively, the studies indicated that interval exercise was significantly more effective at improving VO₂peak compared with continuous exercise. However, observed improvements in ejection fraction were not significantly different between training protocols (Haykowski et al. 2013). Rognmo and colleagues (2004) compared the effects of aerobic interval exercise with moderate intensity continuous exercise in coronary artery disease patients. After 10 weeks of treadmill exercise, patients who performed interval exercise experienced a significantly greater increase in VO₂peak (Rognmo et al. 2004). In a study of diabetic patients, Mitranum et al. (2013) found that 12 weeks of either aerobic interval training or continuous aerobic training conferred various improvements in health, including reductions in body fat, resting HR, and fasting blood glucose, as well as increases in leg muscle strength. However, only the group of patients who performed the interval exercise program significantly decreased glycosylated hemoglobin values, an indication of improved blood glucose control over a prolonged period. In addition, although both groups improved VO₂max, the interval exercise group had a greater increase (Mitranum et al. 2013).

High-intensity interval training may be an effective method to achieve health-fitness benefits while performing for a comparatively shorter time period during each exercise session. Time commitment is a common barrier to exercise participation (Trost et al. 2002). Minimizing the time required for a given exercise session could be a major factor to promote program adherence in some individuals (Kessler et al. 2012; Reichert et al. 2007). In a study by Matsuo et al. (2013), sedentary men who performed 8 weeks of aerobic interval training achieved significantly greater beneficial changes in VO₂max, left ventricular mass, stroke volume, and resting HR compared with those who performed a continuous aerobic exercise training program. The duration of each interval exercise session was 13 min, compared to the 40-min continuous exercise session. The shorter time period required for an interval program could facilitate an individual’s ability to complete exercise sessions within the time they have available for daily PA. However, average caloric expenditure for the interval exercise sessions was 180 kilocalories (kcals) compared to the 360 kcals required during continuous exercise (Matsuo et al. 2013). Therefore, an increased exercise duration or a greater focus on dietary changes may be necessary to achieve weight loss goals when employing an interval program.

The intensity of the exercise intervals may influence the type and size of physiological training adaptations. In a study by Higgins and colleagues (2013), children with cystic fibrosis performed interval exercise by alternating intensity between target OMNI RPE’s 4 and 7. For most individuals, an OMNI RPE 4 represents low to moderate exercise intensity, usually falling below the VT. An OMNI RPE 7 represents high exercise intensity falling above the VT. Studies have examined high-intensity intervals at prescribed HR or VO₂ values of 80–100 % of maximal intensity. This comparatively high intensity range is not only safe and effective for healthy individuals but may also be safe for most patients with coronary artery disease or heart failure who are participating in cardiac rehabilitation programs (Helgerud et al. 2007; Moholdt et al. 2014; Rognmo et al. 2004; Wisloff et al. 2007). Moholdt and colleagues (2013) employed an interval exercise cardiac rehabilitation program where patients performed within an intensity range of 85–95 % of HRmax. They found that those coronary heart disease patients who performed the exercise intensity intervals at the higher end of the prescribed range had greater improvements in VO₂peak. A target RPE of 7 for high-intensity intervals may not be high enough to elicit HR responses within the range of 85–95 % of HRmax. In addition, a target RPE of 4 may not be low enough to allow proper active recovery between high-intensity intervals. Therefore, to ensure optimal target RPE’s that require the production of high-intensity exercise intervals and low-intensity active recovery periods, it may be best to determine which target RPE’s should be used on an individual basis.

Prior to undertaking an interval exercise program, it is important to ensure that the participants are adequately oriented to the scaling procedures necessary to self-regulate exercise intensity using multiple target RPE’s in a single exercise bout. Therefore, a more advanced perceived exertion scale anchoring procedure was developed and has been used in previous investigations involving such an interval type exercise program (Higgins et al. 2013). This procedure allows time for additional practice, feedback, and reinforcement that is not included in the standard scale anchoring procedures already presented in Chap. 5. This advanced anchoring procedure may be helpful for any individual having difficulty understanding how to use a category scale to rate exertion levels, especially young children. In this procedure, the scale anchoring is divided into three distinct phases: low, moderate, and high/maximal exercise intensity. Each phase includes a brief, 2–4-min bout of load-incremented exercise in which physical intensity is increased and the client estimates his or her RPE every 15 or 30 s. In addition, the low and moderate intensity phases include a brief, 2–4-min production bout in which the individual is instructed to perform exercise that elicits a specific level of exertion as indicated by a target RPE. See Appendix F for a detailed description of this advanced perceived exertion scaling procedure.

Even after a comprehensive exercise anchoring procedure has been administered, additional feedback may be helpful during production trials. The physiological values corresponding to the multiple target RPE’s should be measured during the estimation trial. These values should be monitored during the production trial(s) to provide appropriate feedback and reinforcement regarding the accuracy of intensity self-regulation according to a target RPE. Exercise intensity self-regulation error may be more common when the individual is asked to titrate exercise intensity between different target RPE’s a number of times in a single exercise bout. Pre-participation practice exercise trials, or teleoanticipation, may improve prescription congruence and intensity discrimination (Ulmer 1996).