The purpose of this study was to investigate the effects of swimming exercise and combined exercise for 16 weeks, bone mineral density and health-related physical fitness of elementary school boys.
Total twenty-two boys who live in J-gu, Busan metropolitan city came in for experiment. There were 7 swimming exercise group (11.0±1.3 years), 8 combined exercise group (10.6±0.7 years) and control group (11.7±0.7 years). Both swimming exercise group and combined exercise group were trained three times a week for an hour for 16 weeks.
For the analysis, SPSS Ver. 18.0 was used to get mean (M) and standard deviation (SD). One-way ANOVA was applied to confirm the homogeneous test between 3 groups physical character and dependent variable.
To verify mean difference of 3 groups, two-way repeated measures ANOVA was used. If interaction was appeared, changes within 3 groups is analyzed using one-way ANOVA and paired t-test was used for periods.
And the test was used as posteriori tests to verify percentage of differences about 3 groups both during and after the exercise session. The statistical significance level was set at .05.
The conclusions of this study were as follows;

For health-related physical fitness change, there was significant decrease on body fat percentage in the combined exercise group. And there was significant increase on bat-free mass in the swimming exercise group and the combined exercise group. In the case of muscular strength, while there was significant increase in the combined exercise, there was significant decrease in the swimming exercise group and the control exercise group. In addition, there was each significant increase on muscular endurance in the swimming group and the combined group, on flexibility in the combined group, and on cardiopulmonary endurance in the swimming group and the combined group. Also, the effects of interaction between groups and periods showed significant improvement in fat-free mass, muscular strength, muscular endurance, and cardiorespiratory endurance.
For bone mineral density change, there was significant increase on femur shaft, femur total in the swimming exercise group and on L3 in the combined exercise group. And there was significant increase on L2, femur trochanter, femur shaft and femur total in the control exercise group.

In conclusion, regular swimming exercise and combined exercise for grades 4 to 6 elementary school boys have a good effect on their health-related physical fitness.
There is, however, no clear evidence that both exercises have any effect on bone mineral density change. Thus, it needs to perform followup study about the effect of high-intensity and long-term physical activity program on bone mineral density for growth children.