Do Adolescents With Insulin Resistance Demonstrate Impaired Heart Rate Recovery From Exercise?

Abstract

Heart rate recovery (HRR) following maximal aerobic exercise can serve as a noninvasive method of analyzing the risk for cardiovascular diseases. Inability to recover heart rate to pre‐exercise values can indicate parasympathetic nervous system dysfunction. Poor HRR could also be an indicator of early mortality, as decreased ability to recover heart rate is linked to decreases in vagal tone. Insulin resistance (IR) has also been linked to diabetes, obesity, and parasympathic nervous system dysfunction in adults, through an increased ratio of sympathetic to parasympathetic nerve activity. However, it remains unknown if adolescents with IR exhibit similar parasympathetic dysfunction. Therefore, it was hypothesized that increased IR would be associated with decreased HRR in adolescents.Data were collected from adolescents aged 12‐18. Insulin resistance was quantified as HOMA‐IR using fasting glucose and insulin. Subjects underwent maximal aerobic exercise testing on a cycle ergometer pedaling at 60‐70 RPM, starting at 25 W and increasing 25 W every two minutes. The test was terminated when subjects could no longer maintain the pedaling cadence for 5 consecutive seconds. Following cessation of exercise, subjects remained seated without movement for a two‐minute recovery period. Heart rate (HR) was collected via three lead ECG. Data was filtered and resampled to 1 Hz. A linear regression model was applied to the first 30s of HRR data for each subject, with the resulting slope used as the output variable in a subsequent linear regression model with HOMA‐IR as the predictor. Significance was set p<0.05.Subjects were 15 ± 2 years old with a HOMA‐IR 2.08 ± 1.92. The average HRR slope was ‐0.63 ± 0.13 BPM (r=‐0.91). The slope of HRR vs. HOMA‐IR was ‐0.02 ± 0.02 (r=‐0.32, p=0.18). The slope of HRR vs. fasting glucose was ‐0.001 ± 0.003 (r=‐0.07, p=0.8). The slope of HRR vs. fasting insulin was ‐0.008 ± 0.004 (r=‐0.42, p=0.08).Poor HRR has been linked to early mortality, and insulin resistance causes diabetes. However, IR and HRR were not found to have a statistically significant relationship. The relationships between HRR and fasting glucose and insulin levels were also not statistically significant. These data suggest there is no relationship between HRR and IR post exercise in adolescents.