Browsing by Author "Karppinen, Noora"

Heart rate variability (HRV) is a noninvasive tool for investigating cardiac autonomic nervous system, especially its parasympathetic branch. HRV is known to be reduced for example in cardiovascular autonomic neuropathy and after myocardial infarction. Several studies have reported reduced HRV in type 1 diabetes patients. Regular exercise is known to increase parasympathetic tone but the effect of training on HRV is somewhat unclear. This study examined HRV during 48 hours after incremental cycling until volitional fatigue in type 1 diabetes patients without cardiac autonomic neuropathy and in healthy controls. HRV was analyzed both at day and night. Subjects' aerobic capacity was measured. Part of the subjects underwent 6-12 months training intervention, after which the same measurements were repeated. Time-domain, frequency-domain and nonlinear methods were used in HRV analysis. Aerobic capacity was significantly higher in healthy controls than in type 1 diabetes patients (p=0.036). No differences in HRV were found between type 1 diabetes patients and healthy controls. In healthy controls aerobic capacity correlated with LF/HF-ratio (r=-0.711, p=0.014). In type 1 diabetes patients glycosylated hemoglobin (HbA1c) correlated with SDNN (r=-0.645, p=0.023), absolute VLF power (r=-0.648, p=0.023) and SD2 of Poincare plot (r=-0.646, p=0.023). There was a significant increase in aerobic capacity in both groups after training intervention (p<0.05). Training intervention did not cause a significant change in HRV.