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.