EFFECTS OF PHYSICAL-TRAINING ON HEART-RATE-VARIABILITY IN DIABETIC-PATIENTS WITH VARIOUS DEGREES OF CARDIOVASCULAR AUTONOMIC NEUROPATHY

Objective: To investigate the effects of regularly performed endurance training on heart rate variability in diabetic patients with differen t degrees of cardiovascular autonomic neuropathy (CAN). Methods: Bicyc le ergometer training (12 weeks, 2 x 30 min/week, with 65% of maximal performance) was performed by 22, insulin-requiring diabetic patients (age 49.5 +/- 8.7 years, diabetes duration 18.6 +/- 10.6 years; BMI 25 .1 +/- 3.4 kg/m(2)): i.e., by 8 subjects with no CAN, 8 with early CAN and by 6 patients with definite/severe CAN. A standard battery of car diovascular reflex tests was used for grading of CAN, a short-term spe ctral analysis of heart rate variability for follow-up monitoring of t raining-induced effects. Results: While the training-free interval ind uced no changes in spectral indices, the 12-week training period incre ased the cumulative spectral power of the total frequency band (P = 0. 04) but to a different extent (P = 0.039) in different degrees of neur opathy. In patients with no CAN the spectral power in the high-frequen cy (HF) band (0.15-0.50 Hz) increased from 6.2 +/- 0.3 to 6.6 +/- 0.4 In [ms(2)]: P = 0.016, and in the low-frequency (LF) band (0.06-0.15 H z) from 7.1 +/- 0.1 to 7.6 +/- 0.3 In [ms(2)]; P = 0.081 which resulte d in an increase of total spectral power (0.06-0.50 Hz) from 7.5 +/- 0 .1 to 8.0 +/- 0.3 In [ms(2)] (P = 0.05). Patients with the early form of CAN showed an increase of spectral power in HF (5.1 +/- 0.2 to 5.8 +/- 0.1 In [ms(2)], P = 0.05) and LF bands (5.6 +/- 0.1 to 6.3 +/- 0.1 In [ms(2)], p = 0.008), resulting in an increase of total power from 6.1 +/- 0.1 to 6.6 +/- 0.1 In [ms(2)] (P = 0.04), whereas those with d efinite/severe CAN showed no changes after the training period. Traini ng improved fitness in the whole patient cohort. The increased autonom ic tone as assessed by spectral indices disappeared after a training w ithdrawal period of 6 weeks. Conclusion : In diabetic patients with no or early CAN, regularly performed endurance training increased heart rate variability due to improved sympathetic and parasympathetic suppl y, whereas in subjects with definite/severe CAN no effect on heart rat e variability could be demonstrated after this kind of training.