1. FORCE-TIME CHARACTERISTICS OF A COUNTERMOVEMENT JUMP IN ELITE YOUTH SOCCER PLAYERS.
R. Morris1, B. Jones1, J. Lake2, S. Emmonds1, K. Till1. 1.
RESULTS: Descriptive statistics, effect size (ES) and results of one-way analysis of variance are presented in Table 1. Age had a
significant effect on all CMJ force-time characteristics and body mass (p<0.001). Tukey pairwise comparisons revealed impulse had a significant, moderate effect on all consecutive age categories (d=-0.72 to -0.99). Similarly, mean power had a significant, small to moderate effect on all consecutive age categories (d=-0.55 – to 0.84). However, mean net force and JH were not significant (p>0.001) for all consecutive age categories.
PRACTICAL APPLICATIONS: The importance of lower limb explosiveness in soccer is apparent and is usually expressed very quickly (<250 ms). These data suggest the differences in jumping performance between age categories can be attributed to duration of the propulsion phase. However, this may not be realistic within a match scenario (<250 ms). As such, practitioners should look to decrease the duration of the propulsion phase and increase the relative force capabilities of youth soccer players to improve jumping performance.
INTRODUCTION: Vertical jump force-time characteristics, like impulse, mean net force, mean power and jump height are of interest to sports scientists. This information, specifically from a force plate, is limited in youth elite footballers across ages of years. The force plate is considered the ‘gold standard’ for obtaining this information but is often financially and logistically unfeasible. The purpose of this study was to determine the effect of age on the force-time characteristics during a countermovement jump (CMJ).
METHODS: Two hundred nighty three elite male youth soccer players (U18s n = 48; U16s n = 39; U15s n = 45; U14s n = 56; U13s n = 54; U12s n = 51) from 4 professional soccer academies, performed 2 maximal CMJs with arms akimbo on a portable force platform (AMTI, 28 ACP, Watertown, MA, 400 Hz). System weight = the average of 1 s of quiet standing force and was subtracted from force to obtain net force; this was integrated with respect to time to obtain net impulse which was summed over the propulsion phase. Net force was divided by mass to obtain acceleration, which was integrated with respect to time to obtain velocity; force was then multiplied by velocity to obtain power. Jump height was calculated using the velocity at take-off. Force, velocity and power were averaged over the propulsion phase which was identified as shown in figure 1. One-way ANOVA was used to identify the effect of age on net impulse, mean net force, jump height (JH) and mean power. Cohen’s d effect sizes were also calculated between consecutive age categories as a measure of practical significance.
Figure 1. Deconstructed force-time graph 2.
@rhysmorris88

2. U12 (n=51) U13 (n=54) U14 (n=56) U15 (n=45) U16 (n=39) U18 (n=48)
Means ± SD
Impulse (N.s)
91.21 ± 12.07
± 17.95a
± 37.53ab
± 25.58abc
± 26.15abcd
± 23.26abcde
ES = ± 0.34
ES = ± 0.33
ES = ± 0.34
ES = ± 0.38
ES = ± 0.37
Mean Net Force (N) ±
± a ±
± abc
± abcd
± abcd
ES = ± 0.33
ES = ± 0.32
ES = ± 0.33
ES = ± 0.37
ES = ± 0.36
Mean Power (W) ±
± a
± ab
± abc
± abcd
± abcde
ES = ± 0.34
ES = ± 0.32
ES = ± 0.34
ES = ± 0.37
ES = ± 0.36
Jump Height (cm)
0.25 ± 0.0
0.26 ± 0.04
0.29 ± 0.06ab
0.31 ± 0.05ab
0.35 ± 0.05abcd
0.35 ± 0.04abcd
ES = ± 0.32
ES = ± 0.33
ES = ± 0.38
ES = 0.00 ± 0.36
Body Mass (kg)
39.65 ± 5.03
45.04 ± 7.07a
52.49 ± 10.61ab
61.36 ± 8.29abc
66.03 ± 8.27abc
72.64 ± 7.47abcde
ES = ± 0.34
ES = ± 0.34
ES = ± 0.37
ES = 0.73 ± 0.37
U12 (n=51)
U13 (n=54)
U14 (n=56)
U15 (n=45)
U16 (n=39)
U18 (n=48)
Means ± SD
Impulse (N.s)
91.21 ± 12.07
± 17.95a
± 37.53ab
± 25.58abc
± 26.15abcd
± 23.26abcde
ES = ± 0.34
ES = ± 0.33
ES = ± 0.34
ES = ± 0.38
ES = ± 0.37
Mean Net Force (N) ±
± a ±
± abc
± abcd
± abcd
ES = ± 0.33
ES = ± 0.32
ES = ± 0.33
ES = ± 0.37
ES = ± 0.36
Mean Power (W) ±
± a
± ab
± abc
± abcd
± abcde
ES = ± 0.34
ES = ± 0.32
ES = ± 0.34
ES = ± 0.37
ES = ± 0.36
Jump Height (cm)
0.25 ± 0.0
0.26 ± 0.04
0.29 ± 0.06ab
0.31 ± 0.05ab
0.35 ± 0.05abcd
0.35 ± 0.04abcd
ES = ± 0.32
ES = ± 0.33
ES = ± 0.38
ES = 0.00 ± 0.36
Body Mass (kg)
39.65 ± 5.03
45.04 ± 7.07a
52.49 ± 10.61ab
61.36 ± 8.29abc
66.03 ± 8.27abc
72.64 ± 7.47abcde
ES = ± 0.34
ES = ± 0.34
ES = ± 0.37
ES = 0.73 ± 0.37