Exercise prescription
The exercise intensity of the HIIT exercise prescription for OA rats was set according to VO2max, which was 38.6±8.8mL/ (kg‧min) [27]. The rats underwent familiarization training for one week. The training program was as follows: the rats first moved freely on the turned-off treadmill (YS101, Tianjin, China) for 10min, then moved at 5m/min~10m/min for 10min. A total of eleven rats were removed during the exercise, including seven that did not cooperate with the training and four with severe infections in their paw and tails. The number of missing rats in each group was supplemented until all the rats acclimated to the treadmill environment and speed change. HIIT was received as follows: First, warm-up at 10 m/min (30% VO2max) for 3min, and then high-intensity running at 24 m/min (80% VO2max) for 1 min (five cycles), moderate-intensity running at 15 m/min (50% VO2max) for 3min (five cycles), and finally cool down at 10 m/min for 2 min. The interval ratio of high-intensity to moderate-intensity exercise was 1:3, and each exercise was 25 min, three days a week (10:00 am every Tuesday, Thursday and Saturday). The total duration of HIIT exercise training was 75 min/week (Table 1). The other groups were given exercise intervention at a speed of 10 m/min, and the exercise duration and frequency were the same as HIIT.
Table 1 HIIT training protocol for OA rats