The experimental group will undergo 60 minutes of PNF training.

The control group will follow the curriculum standards set by the Sports University.

The subjects underwent rehabilitation training for 8 weeks, three times a week (Monday, Wednesday and Friday, 6:00 PM to 10:00 PM in the Physical Education College of Guangxi Normal University), and the rehabilitation training time was about 40-45 minutes per person. Before each rehabilitation training, the subjects warmed up the ankle and lower leg muscles for 5 minutes, followed by the corresponding rehabilitation training for 30-35 minutes, and relaxed the ankle and lower leg muscles for 5 minutes after the training.

CAIT consists of 9 questions with a total of 30 points, scoring ≦27 points for diagnosis of functional ankle instability, 28 points and above for diagnosis of non-functional ankle instability.

1. Before issuing the questionnaire, explain the contents of the questionnaire to the subjects in detail, and the subjects fill in the questionnaire truthfully according to their own situation.
2. The CAIT score of the subjects was calculated and recorded.
3. If you fill in the questionnaire incorrectly, you need to fill it again and keep a record

The lower limb stability test was carried out by MicroSwing 6.0 gravity center moving trajectory tester made in Germany. The test steps and methods are as follows:

1. Before the test, arrange the subjects to be familiar with the lower limb stability test system and test environment, and master the test method.
2. The subject stands barefoot and one foot in the center of the center of gravity movement trajectory tester, with his hands placed on his sides naturally, and maintains his body balance for 30 seconds.
3. Record data of the test system.
4. The measurement was repeated three times with a time interval of 5min. Collect the test data of the center of gravity moving trajectory tester, including swing frequency, coordination coefficient and stability coefficient, and get the best results of the three tests.

The subjects stood in the center of the star chart with the affected side foot as the supporting foot, with bare feet and one foot in the center. The healthy side foot was extended forward, outward front, outer front, outer back, back, inner back, inner and inner front respectively to the farthest distance as far as possible. The supporting foot was extended in the counterclockwise direction when the left foot was used, and the supporting foot was extended in the clockwise direction when the right foot was used. The subject withdrew the non-supporting foot and resumed standing with both feet and rested for 5 seconds. The data of each extension of the subject was recorded, and the farthest score was measured three times. The furthest results in each direction were standardized with the subjects' lower limb length, and the data were recorded.

(4) The furthest scores in each direction were standardized with the subjects' lower limb length, and the data were recorded.