Rating of perceived exertion versus heart rate for isometric exercise prescription: Reliability and agreement study

BACKGROUND: Previous studies have shown that isometric exercise training reduces systolic blood pressure by approximately 8 mmHg and diastolic blood pressure by approximately 4 mmHg in both normotensive and hypertensive individuals. However, the prescription of isometric exercises can be based on the rating of perceived exertion (RPE) or heart rate (HR) obtained during the maximal incremental isometry test. The reliability and agreement of this test have not been assessed. OBJECTIVES: To analyze the reliability and agreement indicators of HR and RPE during isometric wall squat incremental tests. DESIGN AND SETTING: A reliability and agreement study was conducted at Universidade Federal de Pernambuco. METHODS: Twenty-eight healthy subjects (54% men, 26 ± 5 years) performed two isometric wall squat incremental tests. The test began with a knee joint angle of 135° (knee and leg) progressively reduced by 10° at each stage. Each stage lasts 2 minutes or until voluntary exhaustion. The HR and RPE were obtained during the tests. Reliability and agreement were established using test-retest (paired t-test or Wilcoxon test), intraclass correlation coefficient (ICC), standard error of measurement (SEM), coefficient of variation (CV), and Bland-Altman plots. RESULTS: The HR and RPE increased significantly during both tests. The HR and RPE at each stage were similar between the two test sessions (P > 0.05). Both HRmax (ICC: 0.695, P = 0.002, SEM = 8.1 bpm and CV = 5.8%) and RPEmax (ICC: 0.525, P = 0.036, SEM = 0.4 and CV = 3.6%) presented similar reliability indicators, and no statistically significant differences were obtained between the two test sessions (P > 0.05). The Bland-Altman plots indicated good agreement between HRmax and RPEmax. CONCLUSION: HR and RPE showed similar reliability and agreement during the isometric wall squat incremental test.