Why do I feel chest tightness and shortness of breath after running 6 kilometers in these two days, but I don't feel this way after running.

Sudden strenuous exercise is bound to cause physical discomfort. Possible solutions are as follows: 1 Muscle or soft tissue strain: stop exercising and knead with ghost oil or wind-chasing oil twice a day, so as not to catch the wind. Sudden exercise leads to lactic acid accumulation. Solution: Do soothing exercises regularly every day, such as jogging for half an hour or walking for 40-50 minutes.