The temporal relationship between heart rate recovery immediately after exercise and the metabolic syndrome: the CARDIA study

Aims Slower heart rate recovery (HRR) following exercise is associated with the metabolic syndrome, yet the temporal relationship between the two remains unknown. We investigated the cross-sectional and longitudinal associations of slower HRR following a graded exercise treadmill test (GXT) with metabolic syndrome components and LDL-C. Methods and results Participants aged 18-30 from the Coronary Artery Risk Development in Young Adults study underwent a symptom-limited maximal GXT at baseline (n=4319) and 7 years later. HRR was calculated as the difference between maximum heart rate (HR) and HR 2 min after test cessation. Slower baseline HRR was associated with a higher cross-sectional level but not longitudinal (15 year follow-up) increases in blood pressure, triglyceride, waist circumference, and LDL-C. No cross-sectional or longitudinal association was observed between HRR and HDL-C. In contrast, participants with one or two or more metabolic syndrome components (National Cholesterol Education Program III and American Diabetes Association criterion) at baseline examination had significantly larger longitudinal declines in HRR [-3.48 (P < 0.05) and-5.64 bpm (P < 0.001), respectively] from baseline to year 7, when compared with participants without syndrome components (-2.40 bpm). Conclusion Slower HRR does not precede development of the metabolic syndrome, but appears after syndrome components are present.