Association between resting heart rate, metabolic syndrome and cardiorespiratory fitness in Korean male adults

The present study aimed to investigate the association between metabolic syndrome and cardiorespiratory fitness according to resting heart rate of Korean male adults. A total of 11,876 male adults aged 20–65 years who underwent health examinations from 2010 to 2015 at a National Fitness Centre in South Korea were included. Subjects' resting heart rate, cardiorespiratory fitness (VO2max), and metabolic syndrome parameters were collected. The subjects were divided into 5 categories (<60 bpm, 60–69 bpm, 70–79 bpm, 80–89 bpm, and ≥90 bpm) of resting heart rate for further analysis. We found that elevated resting heart rate was positively associated with body mass index, systolic blood pressure, diastolic blood pressure, triglycerides, and fasting blood glucose levels (p < 0.001, respectively); in contrast, elevated resting heart rate was inversely associated with VO2max (p < 0.001). When resting heart rate of subjects was categorized into quintiles and analysed, the results showed that the relative risk of metabolic syndrome was 1.53-fold higher (95% CI, 1.34 to 1.82) in the range of 60–69 beats per minute (bpm), 2.08-fold higher (95% CI, 1.77 to 2.45) in the range of 70–79 bpm, 2.28-fold higher (95% CI, 1.73 to 3.00) in the range of 80–89 bpm, and 2.61-fold higher (95% CI, 1.62 to 4.20) in the range of ≥90 bpm, compared to those <60 bpm; this indicated that as resting heart rate increased, the relative risk of metabolic syndrome also increased. Resting heart rate of male adults was found to be associated with cardiorespiratory fitness; the risk factors for metabolic syndrome and relative risk of metabolic syndrome increased as resting heart rate increased.