This study examined 4- and 5-year-old children to elucidate effects of playing tag as an intervention for endurance ability in kindergarten children. Two classes in each age group were designated as an intervention group and a control group. Six highly active tag programs were chosen, three tag playing sessions, 70-80 s each, were conducted five times in each intervention. A 20 m shuttle run was used pre-intervention and post-intervention as a test. The test for 20 m shuttle run performance after the 4-week intervention revealed no significant difference between groups of four-year-old children. However, significant improvement was found for the intervention group of five-year-old children. Results suggest that exercise intensities in five-year-old children were higher than in four-year-old children.

This study aimed to investigate the relationship among quadriceps femoris muscle architecture, jump performance, and age in months in junior high school basketball players. Nineteen male junior high school basketball players (age, 13.7±0.7 years［168.1±9.5 months］；height, 166.3±10.3 cm；body mass, 54.3±12.6 kg；competitive career duration, 5.3±1.7 years) volunteered to participate in this study. We measured the vertical jump (VJ) and running jump heights using a single leg (RJS) or both legs (RJB). Quadriceps femoris (vastus medialis oblique［VMO］, vastus medialis［VM］, rectus femoris［RF］, vastus intermedius［VI］, vastus lateralis［VL］) muscle thickness (MT) was measured using real-time ultrasonography. The total MT of the VMO, VM, RF, VI, and VL was calculated (Total). Pennation angle (PA) was measured at the RF and VL. Images were analyzed by an image analysis software and fascicle length (FL) of the RF and VL were calculated by MT and PA. The ratio of MT to body mass^1/3（MT/BM^{1/ 3} ratio) was calculated to normalize the morphological differences. We observed a significant correlation between VJ and MT of the VMO (r＝0.558, p＝0.013), RJB and MT of the VMO, RF, Total (VMO, r＝0.538, p＝0.017；RF, r＝0.483, p＝0.036；Total, r＝0.539 p＝0.017), and between RJS and MT of the VL (r＝0.536, p＝0.018). We also observed a significant correlation between RJB and FL in VL (r＝0.569, p＝0.011). There were significant correlations between MT and MT/BM^{1/ 3} ratio in VMO and age in months (MT, r＝0.659, p＝0.002；MT/BM^{1/ 3} ratio, r＝0.511, p＝0.026). The results of the present study suggest that different parts of the quadriceps femoris muscle are related to jump performance in junior high school basketball players. When growth spurts occur during the age of junior high school student (12-15years old), VMO distal to the VM may increase specifically.