Sports Buffer Zones

By: Andrés J. Calderón, Ph.D.

In the United States, youth sports are often significant family events.  ESPN estimated that approximately 21.9 million children between the ages of 6 and 17 play sports.  Considering all of the games, as well as practice sessions, it is not surprising that sports injuries occur.  One aspect of a sports field or court that is often overlooked is buffer zones. 

A buffer zone is a safety area around a playing field or court that is reasonably free from obstacles and hazards.  Buffer zones are needed because it is difficult during the aggressive actions of play for an athlete to never exit the boundary lines of the field or court.  This is especially true in sports like basketball, football, and soccer.  In these sports it is often required that athletes run at full speed near the boundary lines, either to save, catch, or go after a ball.  These scenarios are typical in many types of sports. 

This topic has incurred significant debate, and there have been several lawsuits over the years to determine the appropriate buffer zone for sports.  However, specific distances are not necessarily standardized by sport.  For example, the NCAA has a distance at which photographers cannot stand near the end line on a soccer field, essentially creating a soccer end line buffer zone.  However, in the National Basketball Association the photographers and spectators are inches away from the side and base lines.  This results in an inherent risk to players and spectators.  Another limitation is the capacity to incorporate reasonable buffer zones for existing courts or fields.  Therefore, it is essential to analyze each sport in its own capacity.  For example, the area behind the basketball hoop and the backboard should be free of obstacles since players will run towards that area and have significant activity near the hoop.  In other words, this is an expected high energy play area.  However, in a soccer field the area directly behind the soccer goal will usually have little to no interaction from the players.  Understanding the biomechanics of the sport and the surrounding area, will be essential to determining the reasonable safe distances for buffer zones and how obstacles that cannot be removed can be made safer where interactions with the athletes may occur.  When obstacles cannot be removed near playing areas (i.e. football goal posts, walls surrounding a court, etc.) padding should be used.  The National Safety Council provides the engineering hierarchy for safety, which simply stated is to eliminate, guard, or warn.  Eliminating a hazard should be the primary focus of this safety practice when readily achievable.  For example, a pole or wall hazard should be eliminated from the buffer zone when reasonably possible; however, when hazard elimination cannot be reasonably achieved, guarding is warranted, such as padding poles or walls.  Of course, guarding reduces the likelihood of an injury and/or the likely severity of an injury, whereas eliminating a hazard prevents an injury.  Therefore, eliminating a hazard is always a primary goal when reasonably attainable. 

Padding is used on hard surfaces that surround sporting venues to increase the time of contact during an impact.  The impulse force or force transmitted during an impact depends on the average force of the impact multiplied by the time of contact between the two objects that collide.  The shorter the contact time is the larger the transmitted force will be to the objects.  The contact time is also referred to as deformation time, for example vehicles are designed with crumple zones in order to extend the contact time between two vehicles.  The increase in contact time or deformation of the vehicle will decrease the forces experienced by the occupants of the vehicle.  This is the same principle on how padding a hard surface works.  By padding a hard surface, the contact time between two colliding objects is increased and thus reduces the impulse or impact force, see Figure 1.

By not maintaining padding on the poles or walls that may be inside a buffer zone the players are placed in a potentially dangerous scenario for injury, especially when considering head injuries.  ASTM F355-95, Standard Test Method for Shock-Absorbing Properties of Playing Surface Systems and Materials is a standard that provides a testing protocol to choose the appropriate padding for its intended use.  There are situations where removing an object in the buffer zone may not be considered to be reasonably attainable and this may be a location where players will foreseeably be exposed to interaction with the hazard when they go out of bounds.  Such locations should be protected by a padded surface to increase the contact or deformation time to limit the transmitted forces to the player.  Therefore, the importance of engaging the right expert to explain the importance of how buffer zones should be designed and maintained is crucial when explaining a hazard and its potential for a sports related injury.  This is of equal importance for both plaintiffs and defendants.  Choose an expert carefully for cases that involve sports injuries with impact to objects or for defects in flooring in the buffer zone which lead to lower limb injuries.  The right expert can make a drastic difference in the outcome of your case.  What they know is important.  Dr. Calderón has not only biomechanical knowledge of sports, but practical knowledge as well.  He has both coached and played various indoor and outdoor sports.  Contact Dr. Calderón for your sports injury related matter.