Association of Metabolic Syndrome with Exercise Capacity and Heart Rate Recovery after Treadmill Exercise Test

Heart rate recovery (HRR) immediately after a treadmill exercise test is a function of vagal reactivation. A delayed heart rate recovery is associated with an increased risk for overall cardiovascular mortality. The purpose of this study is to find out if metabolic syndrome is associated with autonomic nerve function and exercise capacity in healthy adults. We measured the treadmill exercise capacity (METs) and heart rate recovery in 119 subjects through a medical checkup at $J$ General Hospital. The metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria. The value for the HRR was defined as the difference between the heart rate obtained during the peak exercise and the heart rate obtained at first minute during the recovery period. The subjects with the metabolic syndrome had significantly lower exercise duration ($9.6{\pm}1.5$ vs $8.7{\pm}1.4$), METs ($11.6{\pm}1.7$ vs $10.4{\pm}2.5$), and HRR ($37.5{\pm}14.3$ vs $27.1{\pm}8.9$). The waist circumference in subjects with the metabolic syndrome was more strongly correlated with HRR ($r$=-.517, $P$ <.001) than in normal subjects. Furthermore, delayed HRR was associated with high resting heart rate and increased waist circumference ($P$=.032, $P$ <.001, respectively). In conclusion, delayed HRR during the first minute after a treadmill exercise test was associated with the metabolic syndrome risk factors. Delayed HRR was also associated with high resting heart rate and increased waist circumference.