1. Sit-ups: Lie on the ground with your hands crossed on your chest, knees bent and feet on the ground. Then slowly raise your head and shoulders, contract your abdominal muscles, and then slowly lower your head and shoulders. Repeat.

2. Flat support: Lie on the ground, support the ground with both hands, and keep your body in a straight line. Keep this posture for a while, and you can gradually increase the time. This action can exercise the abdominal muscles and core muscles.

3. Alternate belly rolling: lie on the ground, put your hands behind your head and bend your knees. Then lift your upper body with your legs close to your chest, then slowly lower your upper body and repeat.

4. Lie on your back and lift your legs: Lie on the ground, put your hands on your sides, and straighten your legs. Then slowly lift your legs until they form a 90-degree angle with the upper body, then slowly lower your legs and repeat.

5. Running: Running is a systemic aerobic exercise, which can help burn fat and enhance the strength of core muscles. Choose the running intensity and time that suits you and stick to it.

Please note that it is best to consult a doctor or professional coach before doing any exercise to ensure that your physical condition is suitable for these exercises.