Cardiovagal modulation and efficacy of aerobic exercise training in obese individuals

Type 2 diabetes is associated with poor exercise tolerance and peak aerobic capacity (VO2peak) even when compared to obese non-diabetic peers. Exercise training studies have demonstrated improvements in VO2peak among 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: To determine the effects of a 16 wk aerobic exercise program on VO2peak 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/19 men; BMI = 36.1 kg/m) were studied in the fasted state. ECG recordings were obtained while seated for 3 min, prior to and after 4 mo of exercise training (4 d/wk, 65% VO2peak). The ECG recording was analyzed for HRV in the spectral domain. Groups were split on a marker of CVM (normalized high frequency (HFnu)) at the 50th percentile, as either high (H) or low (L) CVM. RESULTS: VO2peak only increased with exercise training among those classified as having HCVM, regardless of diabetes status (T2D: HCVM 20.3 to 22.5 mL/kg/min, LCVM 24.3 to 25.0 mL/kg/min; Obese non-diabetics: HCVM 24.5 to 26.3 mL/kg/min, LCVM 23.1 to 23.7 mL/kg/min) (p<0.05). No change in VO2peak was observed for the LCVM group. Changes in weight do not explain the change in VO2peak among the HCVM group. Glucose tolerance only improved among the LCVM group with T2D. CONCLUSION: Obese individuals, with or without T2D, when classified as having relatively HCVM prior to exercise training, have a greater propensity to improve VO2peak following a 16-week aerobic training program.