Variability in the application of force during the vertical jump in children and adults.

The purpose of this study was to determine if children exhibit greater variability in center of mass movement and kinetics compared with adults in vertical jumping. Countermovement jumps with arms (CMJA) and without arms (CMJ) performed by 20 female children and 20 female adults were examined using force platform. The data were analyzed using continuous methods to determine differences in variability between groups and between types of jump. Jumping variability was measured by using the average coefficient of variation of the force-, velocity-, displacement-, and rate of force development-time curves across the jump. The analysis indicated that children and adults had similar levels of variability in the CMJ but different levels in the CMJA. In the CMJA, the children had a greater coefficient of variation than adults in force- (20 ± 7% and 12 ± 6%), velocity- (41 ± 14% and 22 ± 9%), displacement- (8 ± 16% and 23 ± 11%) and rate of force development-time (103 ± 46% and 75 ± 42%) curves, as well as in force-velocity relationship (6 ± 2% and 4 ± 2%). The results of analysis suggest that the variability depends on both the level of maturation of the participants as well as the task complexity.