Most sports have a certain degree of danger associated with them, due to flying objects and bodies colliding at high speeds. Soccer and water polo are particularly dangerous for one of the most important parts of the human body; the head. Head injury in these sports may stem from contact with the goal posts, other players, the side walls (in water polo) or the ground (in soccer). However, these sports bear a unique danger to the head when compared with other competitive sports due to the nature of ball interaction. Soccer is the only competitive sport that involves and condones purposeful head contact with the ball, while water polo is one of the only sports that involves ball flight almost exclusively in a plane parallel with head altitude. As a consequence of engaging in these sports, risk of head injury, especially concussions due to such ball interactions, is dramatically increased. In 2009 alone, hospitals reported 24,184 cases of soccer head injury, and 28,716 cases of water polo head injury (American Association of Neurological Surgeons – AANS). Furthermore, head trauma in these cases can cause a plethora of disabilities. These can range from loss of motor function to complete paralysis to death in the most severe cases.

The most common of these adverse consequences include the two aforementioned modes of damage. Traumatic Brain Injury, which is defined as a blow or jolt to the head that disrupts normal function to the brain. This is the main, recordable method of brain disruption (AANS). This sort of injury is classified with a set of values known as the GADD severity index, which measures the amount of acceleration of the head as a function of its exponent. This calculation yields a single value that represents the intensity of collision, acceleration, and therefore the danger of the impact. Even more disconcerting, however, is the presence of Chronic Traumatic Encephalopathy, which occurs due to repeated sub-concussive impacts to the head, and can have long lasting effects. This is equivalent to “creep,” in engineering terms, of damage over time to the brain. After many instances of sub-concussive impacts, which seem harmless as the time, damage slowly builds to a critical level. Repeated sub-concussive impacts build up to major concussive levels. These concussions can be much more severe even if the sub-concussive impacts never reached the magnitude of a singular concussive impact (Spiotta, Bartsch, and Benzel 2011). This is a concern for many athletes, as it is hard to gauge how far along the path of CTE one is. CTE’s are quite difficult to study in a limited time span, it will not be a focus of the experiment, although it is still a serious consideration.

The existence of these serious injuries make it critical to reduce the amount of risk taken when participating in these sports. Specifically, our team is searching for methods of minimizing the amount of impact force imparted to the head by ball contact. Interestingly, there is little to no precedent for tests on ball specifications and their implications on impact forces in these two sports.