Optimizing aerobic exercise intensity prescription in cardiovascular rehabilitation: challenges and solutions

Abstract

This doctoral thesis follows a scientific article format, adhering to the norms of both University of Brasília, and Hasselt University. The central theme of the thesis is aerobic exercise intensity prescription in cardiovascular rehabilitation (CR), addressing challenges and optimization strategies across four published articles. In the first article, we studied exercise responses at ventilatory thresholds (VTs) in individuals with cardiovascular diseases assessed during treadmill cardiopulmonary exercise test (CPET), comparing these responses to guidelinedirected intensity domains. We identified inconsistencies and proposed a solution to enhance indirect intensity prescriptions by developing pioneering equations to predict heart rate (HR) at VTs using parameters obtained in exercise tests without gas exchange analysis. In the second article, we examined a multicentric CR database from eight European countries and introduced cycle-ergometer predictive equations for HR at VTs, along with an adjusted percentual for HR reserve (%HRR) prescription. We externally validated our approaches using a South American database with both ergometers, comparing performance to guideline-based exercise intensity domains and exploring ergometer interchangeability. The third article explored sex-specific responses at VTs to determine whether differences in percentages of peak effort and %HRR exist and justify distinct prescription recommendations. The fourth paper offered an updated perspective on prescribing aerobic exercise intensity for CR, examining international guidelines, the accuracy of various approaches, and practical applicability in diverse clinical settings. The thesis’ conclusion points out that current international guidelines vary significantly in their recommendations and show notable inconsistencies with the individual threshold-based responses. Another challenge is the high inaccuracy of the commonly used percentage of peak HR prescription method, emphasizing a significant mathematical limitation in its applicability, previously unreported. When the optimal CPET threshold-based approach is unavailable, our studies revealed that the validated HR at VTs predictive equations and the adjusted %HRR range (42–77%) are the most accurate alternatives for approximating VTs in the CR population. These methods surpass guideline-based HR approaches and demonstrate minimal ergometer-specific effects on HR at VTs estimation. Moreover, current recommended intensity prescription methods for CR populations using percentages of peak effort and %HRR may not require significant sex-based adjustments. Finally, in lower-resource settings, conducting at least a submaximal functional test is essential for assessing individual exerciseresponses and quantifying physical condition. Subjective methods (e.g., Borg rating of perceived exertion, talk test) should complement objective ones to refine intensity prescriptions.