Abstract: To evaluate the effects of 9 months swim drill on maximal aerobic capacity of children, 91 boys and girls aged 8 to 11 years were test ed by using a treadmill running test. Fourty-two swimmers ( 20 boys, 22 girls ) were s elected from the swim team of Haidian amateurish sports school in Beijing ( the trained group ) and 49 untrained ones ( 24 boys, 25 girls ) with the normal physical activity level for their ages from common school ( the control group) .
The result demonstrated that the trained children increased more in body height, weight, lean body mass and vital capacity than those in the control group before and aft er observation. Most increase rates of morphological indicators did not emerge significant differences between two groups during the period of observation. It showed that both the trained and control group had the same velocity of growth. The trained group had great er vital capacity than control one ( especially for boys), it meant that the swim drill would increase respiratory function of children.
The trained group had obviously higher VO2max in absolute value and in several relative values than the control group. There were no significant differences in the increments of most indicators between the trained and control group during the period of observation. But the increments of maximal endurance time and VO2max /HRmax were significantly higher in trained group than in control group of boys. It show ed that the swim drill might improve cardiac and respiratory function of preadolescent boys, but there were no significant effects for girls.

Key words: Swim drill, Children, VO2max