Oxygen uptake efficiency, chronotropic ıncompetence and abnormal heart rate recovery during exercise in individuals with metabolic syndrome

<bold>Aim:</bold> Oxygen uptake efficiency slope (OUES) is an indicator of cardiorespiratory fitness. Chronotropic incompetence (CI) and delayed heart rate recovery (HRR) reflect autonomic dysfunction. We hypothesised that individuals with metabolic syndrome (MetS) might exhibit these responses during exercise, given the known cardiorespiratuar involvement in this population. <bold>Methods:</bold> This study included 37 individuals diagnosed with MetS (12 women, 25 men) and 20 control individuals (6 women, 14 men). We performed a cardiopulmonary exercise test on all participants. HRR is difference between the HR at peak exercise and the HR at the first minute of the cool-down period. HRR of ≤12 beats was considered abnormal. The Chronotropic Response Index (CRI)=[(peakHR-restingHR)x100)/((220-age)-(restingHR)]. CI was defined as a CRI value of less than 80. <bold>Results:</bold> The demographic characteristics of the groups were similar (p>0.05). VO2max (kg/ml/min), expected VO2max (%) and OUES (ml/min/l/min) had lower values in subjects with MetS compared to control subjects (p<0.05). 83.8% of the patients had a low CRI, while only 20% of the control individuals had a low CRI. A statistically significant difference was found in CRI (p<0.01), but no significant difference was found for HRR (p>0.05). <bold>Conclusion:</bold> Individuals with MetS exhibit reduced cardiorespiratory fitness in both maximal and submaximal parameters. CI is indicative of impaired autonomic function. Further studies are needed to investigate the effects of respiratory training and aerobic exercise, which have been shown to be effective in improving autonomic function and cardiorespiratory response in these patients.