Fifty high school students of both sexes with an age range of 17 to 19 years were selected for this study. They included 30 males-half regularly did exercise, while half did not and 20 females-half had regularly engaged in sports activities, the other half did not. Before running, on average males had a lower respiratory rate (RR), but a higher blood pressure and serum creatinine kinase (CK) level. In both sexes, students who regularly engaged in sports habits had a lower pulse rate (PR) but higher serum CK. The latter suggested the possibility of sports injury in the males active in sports. After they ran for a distance of 400 meters, there were increased PR, RR, body temperature, skin temperature and systolic pressure; but a decreased diastolic pressure. These physiological signs recovered within the first hour after running, and then were followed by the decrement of blood pressure for two days. The physiological phenomena caused by this kind of anaerobic exercise were more prominent in the groups of students inactive in sports. As for the serum lactate, it rose immediately after running and markedly declined within the first hour. This suggests that short distance running is a typical anaerobic exercise. After their run, serum CK elevated and persisted for two days in the habitual-exercise students, which confirms again the possibility of muscle injury in these students.