In recent years there has been a great deal of attention paid to head injuries and brain injuries suffered by football players, and whether the cumulative effect of these impacts is detrimental to their health. But too often we overlook the potential dangers of sports that lack the raw, bruising physicality of football. Soccer is the only sport in which players actually use their heads to advance and control the ball. Professional soccer players will head the ball many thousands of times during their careers. Although the effect of any single blow may be minimal, those thousands of impacts can have a serious effect on a player’s ability to think, reason, and concentrate.
But what does a header actually entail, and what are the forces involved? An average soccer ball weighs almost exactly a pound, and can fly through the air at speeds of more than 75 mph. The force applied when such an object strikes the head is just under acceptable force tolerance guidelines used by the automobile industry when studying automobile accidents. However, these raw numbers do not tell the whole story. Proper heading technique places the ball on the bridge of the forehead, where the skull is thickest. Furthermore, the upward, driving motion of a header causes most of the force to dissipate down to the chest. As a result, the average soccer header delivers only about 500 Newtons of force to the head, with even the fastest travelling balls barely breaking 1000 Newtons. For comparison, the average boxing punch delivers about 6300 Newtons directly to the head and face.
Now that we understand how and in what amounts force is delivered during a header, we need to understand the effects of that force. The University of Texas Health Science Center has begun a new study designed to take advantage of technological advances to bring testing equipment to players on the field. The study focused on a high school girl’s soccer team in the Houston area. The researchers attended a practice at which the team worked on headers, then tested the girl’s responses to point and counter-point stimuli. They also tested a dozen other girls who did not play contact sports. The study revealed a small but significant gap between the response times of the soccer players and the control group, with the soccer players performing slightly worse. Furthermore, number of headers, amount of time spent practicing, and number of years playing soccer all had a negative impact on performance in the tests.
This study should not be taken as a sign that soccer is dangerous or that parents should immediately begin pulling their kids out of the sport. This is one test, on one team, during one practice. The researchers admit that they did not follow up with the players, and that their responses could well have returned to normal a few hours later. What this study does demonstrate is that researchers are becoming more aware to the possibility of headers being dangerous, and undertaking studies to learn more. In particular, they are concerned with the finding that years of soccer played may be a significant variable, as this could indicate long-term damage. The University of Texas Health Science Center is expanding its investigation into this matter, and other groups are not far behind.
Although there is no conclusive evidence that headers in general are dangerous, there are a number of situations in which researchers agree the force of the ball represents a serious problem. The first is a poorly executed header. If the player has poor technique, the head is not well supported by the chest and body as it strikes the ball, which prevents the force from being absorbed and greatly increases the amount of trauma to the skull. The second dangerous situation involves young players. Too often, very young players use full-size balls, and the ratio of ball weight to player size creates a dangerous situation. Youth leagues should always use smaller soccer balls designed for children. Finally, older soccer balls can become dangerous as they lose their waterproof coating and begin to take on water. A soaked ball can gain several pounds of weight, and easily injure an unsuspecting player attempting a header.
Soccer, just like most other sports, forces the player to take certain risks. But it is still the most played and watched sport in the world. If you play with proper technique and the correct equipment, you can minimize your risks and enjoy the sport.
 One Newton is the amount of force needed to accelerate one kilogram of mass at a rate of one meter per second squared.