Association between initial and final transient heart rate responses in exercise testingBACKGROUND: The rest-exercise-rest transition is accompanied by rapid and slow heart rate (HR) changes modulated by the branches of the autonomic nervous system. Vagal participation seems to be distinct in these different transitions. Additionally, it is methodologically difficult to determine the best moment and how to measure resting HR. OBJECTIVE: To determine the association between initial (rapid and slow) and final transient HR responses during exercise, considering different forms of measuring resting HR. METHODS: We retrospectively studied 103 non-athlete adults (76 males) who underwent 4-second exercise test to obtain the rapid transient HR response as measured by the cardiac vagal index (CVI), and completed a maximal cardiopulmonary exercise test in exactly 10 minutes. HR changes were measured in the first few minutes of exercise (ΔHR) and recovery (dHR). RESULTS: Modest associations were found between CVI and the three forms of measuring ΔHR, r between 0.27 and 0.31 (p<0.05), and a more significant association between dHR and CVI, r=0.53 (p<0.05). The means of the three measurements of resting HR were different (p<0.05) and showed only reasonable correlations between them (r between 0.64 and 0.76; p<0.05). CONCLUSION: It is important to standardize the measurement of resting HR for the analysis of transient HR responses; small or moderate association between the results of the different transients suggests that partially distinct autonomic mechanisms are involved and that their measurements may provide different and potentially complementary clinical information.
Heart Rate; Exercise Rate; Rest; Exercise
