Association of cardio-pulmonary stress test parameters and heart rate recovery in obese subjects with or without type II diabetes

Background and Objectives: Heart rate recovery at first (HRR-I) and second (HRR-II) minute after exercise is accurate in estimating autonomic nervous system balance, and has been related to risk of cardiovascular events. Our aim was to determine independent predictors of HRR collected during standard cardio-pulmonary stress test (CPT) in a group of overweight/obese subjects without (N=14) and with type 2 diabetes (N=19), as compared to a sample (N=15) of healthy sedentary subjects. Methods: A graded exercise test on treadmill was performed. Oxygen uptake at rest and at peak exercise (VO2max), as well as respiratory exchange ratio at peak exercise was collected. Linear and logistic regression was used to assess association between variables collected at CPT and HRR-I and HRR-II. Results: Age, gender, as well as VO2 and HR at rest were all comparable among groups. VO2max and HRmax were both lower in diabetic patients as compared to healthy and overweight/obese groups (20 ± 4.3 vs. 28 ± 7 vs. 25.1 ± 5 ml/Kg/min respectively, p < 0.01). VO2max had the highest association to HRR-I (R2=0.47) and HRR-II (R2=0.44); VO2max < 28 and VO2max < 29 were the most accurate cut-off values to identify subjects with abnormally low HRR-I and HRR-II. Conclusions: VO2max is an independent predictor of HRR-I or HRR-II, and it is able to discriminate between patients with normal or abnormally low HRR values. Further studies are warranted to test usefulness of a customized exercise program to ameliorate autonomic nervous system balance, therefore reducing global cardiovascular risk.