People with type 1 diabetes (T1D) have an increased risk for autonomic dysfunction and those with poorly controlled blood glucose levels have an increased risk for cardiovascular disease. The purpose of this study was to determine heart rate variability (HRV) and glucose variability (GV) parameters in less than optimally controlled patients (Group 2: A1C ≥ 7.0%, n = 6]) compared to well-controlled patients (Group 1: A1C ≤ 6.9% [n = 7]) during steady state treadmill exercise took and rest.
Methods: Thirteen T1D participants, (32.42 ± 10.46 years), performed steady state treadmill exercise (40% VO2Peak) for 30 minutes. Prior to exercise, participants rested for 30-minutes for determination of resting HRV and GV. Participants wore continuous glucose monitors and a Zephyr Bioharness™ to determine GV and HRV, respectively. Nonparametric, paired samples T-tests were conducted using SPSS 24.
Results: In group 2, there were significant differences between the resting period and treadmill exercise in the (1) root mean score of successive differences (RMSSD) (27.71 ± 13.43 vs. 8.01 ± 3.90; z = -2.201, respectively; p <.05); (2) standard deviation of RR intervals (SDNN) (36.54 ± 16.04 vs. 11.68 ± 6.19; z = -2.201, respectively; p <.05); and (3) the stress index (11.17 ± 5.48 vs. 23.07 ± 6.31; z = -2.201, respectively; p <.05). However, during treadmill exercise, there were no significant differences in GV, compared to a resting period. In group 1, there were no significant differences in HRV, during treadmill exercise compared to the resting period. However, there were significant differences in GV (.26 ± .18 vs. .54 ± .38; z = -2.197, respectively; p <.05)., between resting and exercise period.
Conclusion: This study suggests that during steady state aerobic exercise, people with poorer glucose control exhibit a pattern of metabolic inflexibility; however, HRV decreased with steady state exercise in both groups suggesting that exercise training may help to normalize HRV in patients with poorly controlled glucose levels.
M. Park: None. M. Chu: None. Y. Song: None. M. Sevil: None. A. Cinar: Research Support; Self; Dexcom, Inc., JDRF. Stock/Shareholder; Self; Dexcom, Inc., Eli Lilly and Company, Insulet Corporation, Medtronic, Novo Nordisk A/S, Tandem Diabetes Care. L.T. Quinn: None. U.G. Bronas: None.