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. 2009 Oct;33(10):1198-206.
doi: 10.1038/ijo.2009.145. Epub 2009 Aug 4.

Plasticity of heart rate signalling and complexity with exercise training in obese individuals with and without type 2 diabetes

J A Kanaley  1 , S Goulopoulou, R M Franklin, T Baynard, M E Holmstrup, R Carhart Jr, R S Weinstock, B Fernhall
Affiliations

Plasticity of heart rate signalling and complexity with exercise training in obese individuals with and without type 2 diabetes

J A Kanaley et al. Int J Obes (Lond). 2009 Oct.

Abstract

Objective: To examine the responsiveness of cardiac autonomic function and baroreflex sensitivity (BRS) to exercise training in obese individuals without (OB) and with type 2 diabetes (ObT2D).

Design: Subjects were tested in the supine position and in response to a sympathetic challenge before and after a 16-week aerobic training program. All testing was conducted in the morning following a 12-h fast.

Subjects: A total of 34 OB and 22 ObT2D men and women (40-60 years of age) were studied.

Measurements: Heart rate variability (HRV) was measured at rest via continuous ECG (spectral analysis with the autoregressive approach) and in response to upright tilt. The dynamics of heart rate complexity were analyzed with sample entropy and Lempel-Ziv entropy, and BRS was determined via the sequence technique. Subjects were aerobically trained 4 times per week for 30-45 min for 16 weeks.

Results: Resting HR decreased and total power (lnTP, ms(2)) of HRV increased in response to exercise training (P<0.05). High frequency power (lnHF) increased in OB subjects but not in OBT2D, and no changes occurred in ln low frequency/HF power with training. Upright tilt decreased lnTP and lnHF and increased LF/HF (P<0.01) but there were no group differences in the magnitude of these changes nor were they altered with training in either group. Tilt also decreased complexity (sample entropy and Lempel-Ziv entropy; P<0.001), but there was no group or training effect on complexity. BRS decreased with upright tilt (P<0.01) but did not change with training. Compared to OB subjects the ObT2D had less tilt-induced changes in BRS.

Conclusion: Exercise training improved HRV and parasympathetic modulation (lnHF) in OB subjects but not in ObT2D, indicating plasticity in the autonomic nervous system in response to this weight-neutral exercise program only in the absence of diabetes. HR complexity and BRS were not altered by 16 weeks of training in either OB or ObT2D individuals.

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Figures

Figure 1
Figure 1
The effects of upright tilt and pre/post training responses on total power (lnTP), high frequency (lnHF) and low frequency to high frequency ratio (lnLF/HF). *P<0.05 resting pre vs. post in obese (OB) individuals; †P<0.000 supine vs. upright. Obese individuals with type 2 diabetes (ObT2D)
Figure 2
Figure 2
Changes in HR complexity. A. SampEn, B. LZEn. *P<0.01 supine vs. upright tilt; ** P<0.01 position x group interaction, OB subjects had a greater decrease than the ObT2D; OB=obese, ObT2D=obese with type 2 diabetes.
Figure 3
Figure 3
Changes in baroreflex sensitivity with training and upright tilt in all groups. *P<0.01 supine vs. upright tilt; ** P<0.01 position x group interaction, OB subjects had a greater decrease than the ObT2D; †P<0.06 training effect on upright tilt; OB=obese, ObT2D=obese with type 2 diabetes.
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