Heart Rate During Exercise in Type 2 Diabetes

The resting heart rate (HRrest), maximum HR (HRmax), HR recovery (HRRTEST), delta HR recovery (ΔHRRTEST) were measured by continuous telemetric heart rate sensor (Polar FT4, PolarTM, Finland) during an incremental exercise test designed to obtain maximum oxygen consumption (VO2max) on a cycle ergometer (Lode Corival, Groningen, The Netherlands) similar with previous studies using similar cohort. An indirect calorimetry/ergospirometry system (Ultima CPXTM metabolic system, Medgraphics, Minnesota, USA) was used to measure VO2max until volitional exhaustion. Thus, the modified Astrand volitional protocol was applied in the participants of all NG, Pre-T2D and T2D groups increasing the load (i.e., Watts) 25 W each 2 min to women, and 50 W each 2 min to men.

Subjects also participated in a single HIIT session composed of 10-cycling intervals, using a Lode Corival cycle ergometer. The exercise session consisted of 1-minute cycling at high intensity (workload during each interval was set at \~80-100 % maximal power achieved during the incremental exercise test with a workload that allowed to work until the volitional muscle failure in 1-minute), followed by 2-minutes of inactive resting period (sitting still on the cycle ergometer), and was repeated 10 times (1x2x10 protocol; 1:2:10 to work:rest:repetitions respectively).