THE USE OF RATINGS OF PERCEIVED EXERTION FOR EXERCISE PRESCRIPTION INPATIENTS RECEIVING BETA-BLOCKER THERAPY

The ratings of perceived exertion (RPE) scale has received widespread acceptance for gaining a subjective estimate of work intensity and as a means of monitoring and regulating exercise intensity across a varie ty of populations. The original premise for the use of the scale was i ts high correlation with heart rate (HR). Although individual correlat ions between HR and RPE in individuals on beta-blocker therapy are pro bably as high as in untreated individuals, there is evidence to sugges t that the RPE response is mediated at a given work rate, particularly at higher absolute work rates. The variation in the RPE response appe ars to be mediated by the type of beta-blocker therapy administered. I n the interests of safety it is necessary for the exercise specialist to develop at least a basic understanding of the mechanism and effects of beta-blocker therapy as they relate to exercise prescription. beta -Blocking drugs cause a decrease in HR and cardiac output at rest and during exercise, a decrease in myocardial contractility and a decrease in coronary and muscle blood flow. These effects can initiate prematu re fatigue and apprehension in the exercising patient. In the light of these responses, the RPE scale provides important information and may be used to increase the accuracy of monitoring and the prescription o f exercise intensity in the cardiac population. While results regardin g the use and accuracy of the scale during beta-blocker treatment are equivocal, this appears to be due mainly to variations in dosage of th e drug, the mode, intensity and duration of exercise and the health st atus of the individuals used. Overall, the RPE scale appears to be an appropriate monitoring tool, particularly when it is used after a lear ning period. It is concluded that nonselective beta-blockade therapy i ncreases RPE, particularly localised RPE. This could be attributed to a decreased blood flow and oxygen delivery to the muscle and altered g lycolytic metabolism, which increases local muscle fatigue. There is n o evidence to suggest a decrease in the total level of oxygen consumpt ion at given work rates. However, as beta-blocker therapy reduces the maximal oxygen consumption (Vover dotO(2max)) attainable, this serves to increase the exercise intensity at all work rates. Thus, for a give n absolute work rate, the RPE response is higher. However, when the wo rk rate is expressed as a proportion of the Vover dotO(2max) attainabl e during beta-blockade, the differences in RPE are minimised or disapp ear. Although the evidence is not conclusive, it appears that cardiose lective beta-blocker therapy does not have such profound effects on th e RPE response, compared with nonselective beta-blocker therapy, when this is expressed as a proportion of Vover dotO(2max). However, locali sed RPE tends to be higher for nonselective beta-blocker therapy. Thus , the evidence indicates that RPE can be used to estimate exercise int ensity, provided the specific effects of the type of beta-blocker ther apy on local and central fatigue (and local and central RPE) are taken into account. Studies which have examined the effects of an endurance training programme during beta-blocker therapy have shown that RPE ar e decreased at given work rates after training. This has been observed for cardioselective and nonselective beta-blocker therapy, and local and central RPE. There is also some evidence to suggest that the RPE c an be used as the controlling variable to regulate the exercise respon se. Patients on cardioselective beta-blocker therapy produce similar e xercise intensities to other cardiac patients who are not receiving be ta-blocker treatment.