These seemingly harmless jokes belie a real concern of soccer parents: heading and head injuries in soccer.
Soccer is a unique sport in that players can control and advance the ball with their head. At the World Cup in June, Germany scored six of their eight goals against Saudi Arabia with headers. Last year, however, the leading scorer in Algeria died following complications when he landed head-first after losing his balance in the air while competing for a head ball.
Such examples raise a number of questions: Are there dangers from purposeful ball-to-head contact? Are there dangers from accidental ball-to-head contact? How dangerous is it for the head when contacting a hard surface like another players head, foot, elbow, etc? These questions have lead to the consideration of head protection in soccer.
Mechanics of heading
Heading is a complex skill involving the coordination of many body parts, complicated by standing, walking, running forward or backward, jumping when challenged by an opponent, or diving.
The idea is to contact the ball on the forehead at or near the hairline, roughly in the area where you would place your hand to detect a fever. The motion is active; coaches tell their players, Hit the ball, dont let the ball hit you.
The trunk is hyper-extended, the chin is tucked toward the chest, and the neck muscles are contracted. This is important because contracting the neck fixes the head to the trunk, which provides a larger body mass overcoming the velocity of the ball.
The more the trunk is extended, the faster the eventual forward velocity of the trunk and impact on the ball. The arms are usually extended for balance and to protect the player from other players. If jumping is involved, the hips are slightly extended and flexed at the knee just before ball contact. This happens during "straight-on heading." The skill varies when the ball is redirected.
The skilled player requires precise timing of all limbs, trunk, hips, neck, and head. Contact with the ball should be made at the top of a jump, and the trunk is flexed to generate force on the ball. Failure to contract the neck muscles upon contact can result in the head being pushed backward, decreasing control of the ball.
Coaching books rarely discuss heading for players younger than 10 - 12 years old. Heading is an insignificant part of the game before age 12 - 14 years. Teaching the skill of heading to very young players takes time from more valuable skills that might actually get used in a game.
Among very young players (5 - 9 years old), heading is a novelty as head contact is made with a bounced ball traveling at a very low velocity.
Mechanics of impact
It is difficult to accurately measure the impact of a ball on the head. But there are some common sense practices that can protect the young player. Most importantly, players should use the proper ball size for their age group (#3 for ages 6 - 9; #4 for ages 10 - 13; and #5 for 14 and older).
About 50 percent of hand and wrist fractures in young goalkeepers were caused by use of an adult ball that was shot by an adult.
The mechanics of impact are determined by the relationship f = ma, where f = the force of impact, m = the mass of the object, and a = the acceleration of the object at any instant in time.
In this equation, the ball is the object of interest, but one must not forget about the mass of the object hitting the ball. This is an important distinction; a ball hitting a prepared head is hitting a large object because the mass of the player is much greater than the mass of the ball. However, an unprepared head presents only the mass of the head vs. the mass of the ball; in this case, accidental contact with the head can lead to a head injury.
Can a kicked ball lead to a concussion? This is most likely to happen when an unprepared player accidentally gets struck with the ball. The ball velocity necessary to potentially lead to a concussion in a prepared head is in excess of 100 mph (well beyond what anyone could kick).
Another factor to consider is head motion after contact is made. Rotational impact (as in many accidental ball-to-head contacts where a player not paying attention is struck on the side of the head by a goalkeeper punt) is thought to be more injurious to the brain than linear impact (as occurs in most prepared headers).
Mechanism of head injury in soccer
Purposeful heading does not appear to be the real issue in discussions of concussion. Although concussions do occur in soccer, it is not purposeful heading of a ball that causes injury. Most all concussions are caused by head contact with some other hard object, such as another head, an elbow, a foot, knee, goal post, or the ground.
In womens soccer, there are a number of head-to-head injuries; however, in mens soccer, there seem to be more elbow-to-head injuries. Players losing their balance in the air often hit the ground with their head, which can lead to a more serious injury (like that Algerian player I mentioned).
Thankfully, these more serious injuries are extremely rare in soccer. Among high-school players, a team might expect a concussion about once every four to five seasons. In college, a team might see upwards of one concussion per season. Some high schools report concussion rates similar to those at the college level, and professional teams might see even more.
As the level of play increases, so does the incidence of concussion (and most other injuries). Nevertheless, the incidence of concussion in soccer is lower than in other sports like football, hockey, wrestling, and gymnastics.
Whenever parents of young soccer players gather, talk often turns to head protection. There are a number of devices on the market, and one suburban Milwaukee school district actually mandated head protection for middle school players.
The problem is with the perception of the problem and the design of the products. The perception is that purposeful heading can lead to brain injury and this is incorrect. Concussions and repeated heading are two separate entities.
As has been stated, mathematical modeling of heading shows that the ball velocity necessary to potentially cause a concussion in a prepared head is greater than any ball velocity ever recorded (over 100 mph). No one knows the effect of repeated subconcussive impacts.
But the fact that non-concussed soccer players have no real differences in cognitive function would suggest that purposeful heading is not a concern. Longitudinal research is needed for this question.
The design of the products is directed at the misperception that heading is the issue. These products provide padding around the forehead of the player where they would head the ball. However, damaging head injuries like concussion come from a hard object hitting anywhere on the head, such as two players competing for the same air ball. When their heads collide, one or both may be concussed, but the contact points are usually not where the ball would contact the head.
This also applies when an elbow hits the opponent on the side of the head. Furthermore, there are a number of head-to-nose or -chin contacts in which a player below jumps up and into the player behind, causing a whiplash type of injury.
Head contact with the ground often occurs at the back of the head when an opponent undercuts the player.
I havent seen any product currently on the market that would protect players from these injuries, because what they protect is not what typically is injured.
Cognitive function of soccer players
Some early studies out of Norway have suggested heading as a cause of cognitive deficits like concentration and short-term memory. However, studies of American, Swedish and Dutch players have failed to demonstrate long-term deficits following repeated heading or increased exposure to soccer.
Numerous well-controlled, cross-sectional studies have concluded that concussions not heading are behind any cognitive deficits. Unfortunately, there are no published longitudinal studies on changes in cognitive function in players without head injury. Both the English FA and U.S. Soccer have begun longitudinal studies on this topic.
There is no scientific evidence to suggest that heading in soccer is unsafe for soccer players. Concussions in soccer are rare compared to other popular sports and most likely occur from accidental head-ball contact or when the head contacts a hard object like the ground, post, head, foot, knee, or elbow.
Soccer coaches should always use age-appropriate soccer balls when teaching heading and other soccer skills. Although it appears that current protective headgear design will not protect the head from concussion, further study is needed.