Running in situ is helpful for fitness in the following aspects:

1. Aerobic exercise: Running in situ is an aerobic exercise, which can improve cardiopulmonary function and enhance the health of cardiovascular system. Long-term running in situ can effectively reduce the risk of cardiovascular disease.

2. Burn calories: Running in situ is an efficient calorie burning exercise, which can help you lose weight and control your weight. Running in situ can burn about 10- 15 calories per minute.

3. Improve physical endurance: Running in situ can enhance the strength and endurance of leg muscles and improve the endurance and explosiveness of the body. By gradually increasing the running time and speed, the endurance level of the body can be gradually improved.

4. Improve mental health: Running in situ helps to release stress and anxiety and promote physical and mental relaxation. Exercise can promote the brain to release dopamine and other happy hormones, and improve mood and happiness.

5. Convenient and easy to operate: In-situ running does not need additional equipment and venues, and can be carried out indoors or outdoors without being affected by weather conditions. Therefore, it is a very convenient and easy fitness method.

In a word, running in situ is a simple and effective way to keep fit, suitable for people of all ages. It can provide full-body exercise, help improve heart and lung function, burn calories, and improve physical endurance and mental health.