Assessment of Cardiovascular Parameters on Submaximal Treadmill Exercise in Obese versus Nonobese Adults.

Background: Obesity and overweight, irrespective of metabolic status, confer an increased risk of adverse consequences including cardiovascular diseases (CVDs). The mechanisms underlying altered cardiovascular responses in obese individuals during and after submaximal treadmill exercise are the subjects of great interest to public health. After graded exercise, delayed heart rate recovery (HRR), exaggerated blood pressure (BP) response, and prolongation of QT interval are the powerful predictors of cardiovascular morbidity and mortality that may facilitate timely identification of individuals at risk of CVD and help to evaluate the effectiveness of treatment interventions.

Aim: To compare the cardiovascular parameters on submaximal treadmill exercise in obese and nonobese adults.

Materials and methods: This study was conducted on 80 subjects, 40 obese (cases) and 40 normal-weight individuals (controls), belonging to the age group of 18-60 years. Each participant was subjected to submaximal treadmill exercise according to the Bruce protocol. Heart rate (HR), systolic BP and diastolic BP (SBP and DBP), mean arterial pressure (MAP), QT and corrected QT (QTc) intervals, and rate pressure product (RPP) were measured preexercise, immediately after exercise, and during passive recovery at 1 min and 5 min after exercise. The Chi-square test and Mann-Whitney U-test, whichever is appropriate, were employed for the comparison of variables between the two study groups. P < 0.05 was considered statistically significant.

Results: Mean HR immediately after exercise, at 1 min and 5 min postexercise was significantly higher in obese when compared to nonobese participants (P = 0.006, P = 0.001, P = 0.001) despite similar resting HR in both the groups (P = 0.874). Mean SBP, DBP, MAP, and RPP were significantly higher in obese in comparison to nonobese subjects in all stages, i.e. before exercise, immediately after exercise, at 1 min and 5 min after exercise. QT and QTc intervals were also found to be significantly greater in obese than nonobese subjects in all stages (P = 0.001 each).

Conclusion: Obese subjects had higher resting BP (SBP, DBP, and MAP), QT/QTc interval, RPP, and increased response to submaximal treadmill exercise activity. Delayed HRR after exercise was also noted in obese subjects which indicates that obese populations are at risk of developing CVDs due to alteration in autonomic functions with sympathetic hyperactivity.