The effects of body mass index on peak aerobic capacity in post myocardial infarction patients

Abstract

The purpose of the study was to examine the influence of adiposity on the aerobic capacity of post myocardial infarction patients (PMIP) during the early stages of cardiac rehabilitation. One hundred and sixteen recent PMIP were divided into four groups of similar age and height according to their body mass index (BMI) above or below a BMI of 25, and with or without beta blockade. They undertook a graded exercise test (modified Bruce protocol) on a motorised treadmill until volitional cessation or reaching any of the American College of Sports Medicine (ACSM) criteria. Ratings of perceived exertion (RPE)_and blood pressure were recorded every 3 minutes during the exercise. Oxygen uptake (̇O 2 ), respiratory exchange ratio and heart rate (HR) were recorded every 30 seconds during the exercise and a 12-lead electrocardiogram was monitored continuously. The results showed that both groups with a BMI <25 had a longer exercise time ( P <0.05), a higher measured peak ̇O 2 ( P <0.05), and a lower functional aerobic impairment ( P <0.01). When̇O 2 was expressed at a standard RPE of 13 relative to the blockade group of BMI<25, the other groups had a peak ̇O 2 of 90% (non-blockade, BMI <25), 75% (blockade, BMI>25) and 70% (non-blockade, BMI>25) respectively. Peak heart rate and rate pressure product did not distinguish between adiposity groups, but, as expected, did show differences between patients with and without beta blockade. It is evident that adiposity is compromising functional and metabolic measures during exercise but less so in patients on beta blockade. Reducing a patient's BMI to below 25 will have particular benefits for functional aerobic impairment and should be included in early rehabilitation.