Table 1. Estimated ball velocity for an HIC=1000.
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Age (years) H/B mass ratio Accidental Impact H+T/B mass ratio Intentional Impact 6 8.20 7.06 m.s−1 28.71 20.44 m.s−1


The results of this study provide significant information for future studies on head injuries in soccer. The results of this study that a change in the inflation pressure between 10 psi and 14 psi has little effect on the peak impact force. The similarity between the peak impact force curves allow the HIC curves to be created using the properties of a 12psi ball.The results of this study indicate that 18-year old boys can sustain head injuries from accidental ball impact when the ball is traveling close to 9.5 m.s−1 and for 18-year old girls injuries can occur at velocities close to 8 m.s−1. In both cases, the velocities are below the reported ball velocities observed in professional (25.60 m.s−1) and unskilled (19.92 m.s−1) soccer games. However, the ball velocities in children’s games are not well known, but would be below the reported velocities for both professional and adult players (Levendusky et al., 1988). An important result to emerge from this work is the difference between accidental and intentional impact. By increasing the contacting mass, the risk of head injuries is decreased; hence the player with a prepared head (i.e. neck muscles contracted to fix head to the truck) has less chance of incurring head injuries as compared to the player with an unprepared head. In addition, these results indicate the importance of teaching players to use proper technique when heading the soccer ball, meaning the player should tighten the muscles around the neck and actively head the ball instead of allowing the ball to hit him or her.