An attenuated heart rate recovery (HRR) immediately after exercise is considered an index of autonomic imbalance and is a predictor of all cause mortality in patients with type 2 diabetes (T2D). Because autonomic dysfunction in T2D patients has shown to be reversible with glycemic control, weight loss, and fitness gain, we investigated the effect of a 12 week aerobic exercise (AE) intervention compared to standard care on HRR in patients with T2D.
T2D patients (n=32) were randomized to a 12-week AE intervention (n=19) or standard of care (n=13). The AE intervention consisted of supervised exercise training for 1h/day 5/wk for 12 weeks at 80% VO2peak. All subjects completed body composition analysis (DEXA), oral glucose tolerance test (OGTT), and maximal exercise testing before and after the study period. HRR was measured every minute for 10 minutes after cessation of maximal exercise testing.
Baseline HRR 1-minute values were negatively associated with ASCVD Risk (rho = 0.623; p = 0.002) and positively associated with VO2peak (rho = 0.361; p = 0.042). Body weight was unchanged in both control (p = 0.989) and AE group (p = 0.248) after the study period. Following AE training intervention, VO2peak increased by 7.4 ± 1.9% (p < 0.001), glucose metabolism, as measured by OGTT area under the curve (AUC), improved by 11.6 ± 6.0% (p = 0.040), and HRR 1-minute increased by 10.4 ± 6.1% (p = 0.234). The control group showed no significant changes as VO2peak increased by 0.7 ± 2.6% (p = 0.826), AUC improved by 3.1 ± 3.5% (p = 0.585), and HRR 1-minute increased 3.9 ± 9.0% (p = 0.915). Baseline HRR predicted change in HRR after the study period in the control group (rho = −0.817; p = 0.002) but not in the AE group (rho = −0.054, p = 0.860). Upon controlling for baseline HRR, AE group possessed a significantly higher post intervention HRR 1-minute value than control by 28.5% (p = 0.036). We found the AE group also had higher HRR values than control during the post-intervention 10-minute recovery resulting in a main effect of group (p < 0.001).
T2D patients with higher HRR, only receiving standard of care, are more susceptible to chronic detriments in HRR indicative of gradual autonomic function loss. To our knowledge these are the first data showing regular moderate-vigorous intensity exercise, which improved glycemic control and fitness gain independent of weight loss, outperforms standard of care alone for greater HRR.
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