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Cardiovagal Modulation and Efficacy of Aerobic Exercise Training in Obese Individuals

BAYNARD, TRACY1; GOULOPOULOU, STYLIANI2; SOSNOFF, RUTH F.3; FERNHALL, BO1; KANALEY, JILL A.4

Medicine & Science in Sports & Exercise: February 2014 - Volume 46 - Issue 2 - p 369–375
doi: 10.1249/MSS.0b013e3182a66411
Applied Sciences

Type 2 diabetes (T2D) is associated with poor exercise tolerance and peak aerobic capacity (V˙O2peak) even when compared to obese nondiabetic peers. Exercise training studies have demonstrated improvements in V˙O2peak among patients with T2D, yet there is a large amount of variability in this response. Recent evidence suggests that cardiac autonomic modulation may be an important factor when considering improvements in aerobic capacity.

Purpose This study aimed to determine the effects of a 16-wk aerobic exercise program on V˙O2peak in obese individuals, with and without T2D, who were classified as having either high or low cardiovagal modulation (HCVM or LCVM) at baseline.

Methods Obese individuals (38 women and 19 men; body mass index = 36.1 kg·m−2) were studied in the fasted state. ECG recordings were obtained while seated for 3 min, before and after 4 months of exercise training (4 d·wk−1, 65% V˙O2peak). The ECG recording was analyzed for HR variability in the spectral domain. Groups were split on a marker of CVM (normalized high frequency (HFnu)) at the 50th percentile, as either HCVM or LCVM.

Results V˙O2peak only increased with exercise training among those classified as having HCVM, regardless of diabetes status (T2D: HCVM = 20.3–22.5 mL·kg−1·min−1, LCVM = 24.3–25.0 mL·kg−1·min−1; obese nondiabetics: HCVM = 24.5–26.3 mL·kg−1·min−1, LCVM = 23.1–23.7 mL·kg−1·min−1) (P < 0.05). No change in V˙O2peak was observed for the LCVM group. Changes in weight do not explain the change in V˙O2peak among the HCVM group. Glucose tolerance only improved among the LCVM group with T2D.

Conclusions Obese individuals, with or without T2D, when classified as having relatively HCVM before exercise training, have a greater propensity to improve V˙O2peak after a 16-wk aerobic training program.

1Integrative Physiology Laboratory, Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL; 2Department of Physiology, Georgia Regents University, Augusta, GA; 3Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL; and 4Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO

Address for correspondence: Tracy Baynard, Ph.D., Department of Kinesiology and Nutrition, University of Illinois at Chicago, 1919 W. Taylor St., MC-517 Chicago, IL 60612; E-mail: tbaynard@uic.edu.

Submitted for publication June 2013.

Accepted for publication July 2013.

© 2014 American College of Sports Medicine