Myocardial oxygen consumption at rest and during submaximal exercise: effects of increased adiposity

Overweight and obesity are major risk factors for cardiovascular diseases. The objective of this study was to determine the effect of increased adiposity on myocardial oxygen consumption at rest and during submaximal exercise in young adults. The study consisted of 85 young adults (18-22years) grouped into 3 based on their body mass index as normal (NW, n=30), overweight (OW, n=25) and obese (OB, n=30). Steady dynamic exercise test equivalent to Grade 2 Bruce protocol was carried out on treadmill for 5min. Blood pressure and heart rate were recorded before, during 3^rd min of exercise, immediately after cessation of exercise and during 5^th min of recovery. MVO₂ was measured by the Rate Pressure Product (RPP) calculated as product of heart rate and systolic blood pressure. Statistical analysis was done using ANOVA and regression analysis. The mean resting RPP was significantly higher in overweight and obese groups when compared with the normal weight group (p<0.05). There was significant increase in RPP changes to exercise [mean difference in NW-8270.93 bpm.mmHg (99.61%), OW-10593.12 bpm.mmHg (118.39%) and OB-10897.33 bpm.mmHg (118.10%), p< 0.05] and the value did not return to baseline after 5 mins of recovery in study groups (p< 0.05). BMI and Waist stature ratio were the most important independent parameters in prediction of RPP. The study shows that overweight and obese young adults have elevated resting RPP and much higher RPP response to exercise indicating increased (MVO₂) at rest and during exercise suggesting higher hemodynamic stress to the heart.