HIIT Paradigm

Mice in the HIIT group were familiarized with five bouts of treadmill running (4 min × (20–22) m/min) and active rest (2 min × 10 m/min) for 5 days. After familiarization, the mice completed 6-week HIIT. They were exposed to the HIIT exercise protocol for five consecutive days each week. This exercise regime has been previously described (Morland et al., 2017). Briefly, each session consisted of warm-up (10 min × 10 m/min), followed by 10 bouts of 4 min high-intensity running (4 min × (80–90)% Speed_max), and separated by active rest (2 min × (40–50)% Speed_max). Running took place on a treadmill at a 0 degree (Figure 1A). The maximal speed test for mice was, respectively, performed at the end of adaptive training, the second and the fourth week of training, and adjust the speed of interval training (Figure 1B). In this regard, the beginning speed of mice was 10 m/min for lasting 10 min to warm up. Then the speed was increased by 2 m/min every 2 min until exhaustion. Throughout the experiment, the Ctl group did not receive any exercise training.

The exercise paradigm of 6-week HIIT and exercise performance in the maximum test. (A) The exercise paradigm of 6-week HIIT. In the first and second week, the HIIT group completed warm-up (10 min × 10 m/min) and then 10 bouts of high-intensity running [4 min × (22–23) m/min], and separated by active rest (2 min × 10 m/min). In the third and fourth week, the HIIT group completed warm-up and then 10 bouts of high-intensity running [4 min × (26.5–28.5) m/min], and separated by active rest [2 min × (12–14.5) m/min]. In the fifth and sixth week, the HIIT group completed warm-up and then 10 bouts of high-intensity running [4 min × (30–33) m/min], and separated by active rest [2 min × (12–15) m/min]. (B) The exercise performance in the maximum test. The exercise performance of the HIIT group was, respectively, performed at the end of adaptive training, the second and the fourth week of training.