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Ensuring the Safety of Your Gym Floor

Church leaders need to take time to evaluate several factors when making the decision for the type of athletic flooring in their facilities. These factors include the programming and mission of the facilities, the types of activities they will host, initial cost, the relative importance of each type of activity, life-cycle cost, and maintenance costs, to name a few. 

One factor that should rise to the top of the list is safety. When we are talking about the safety of an indoor athletic surface, we can evaluate it in three ways: shock absorbency, impact attenuation, and surface friction.

This article will give a general overview to each of these aspects. This is not designed to be a science lesson in physics or an engineering project for these performance factors. The goal is to provide you with some basic, unbiased information regarding floor safety to aid in the decision-making process.

1. Shock Absorbency
Proper shock absorption should be considered highly important. As an athlete impacts a sports surface, the impacting force is translated into two resultant forces: one absorbed by the floor and the other returned to the athlete. While hard surfaces such as concrete and asphalt provide little or no force reduction for the athlete upon impact due to running or jumping, a safe sports floor system should absorb a certain amount of these forces and are rated by the percentage of force reduction they provide as compared to hard surfaces. For example, a sports floor with a force reduction value of 40 percent will absorb 40 percent of the impact force and return 60 percent of that force to the athlete.  It is widely accepted in the indoor sports flooring industry that the minimal desired percentage is 50 percent. The general majority of wood gymnasium floors installed at the high school level and above will meet this rating; however, there are exceptions. Contrast this to the general majority of synthetic gym floors (rubber, urethane, PVC) installed over concrete, and their average is closer to 30 percent. This is why nearly every athlete, coach, participant, and official will acknowledge that synthetic floors are “harder” and “worse on my joints.” This measurement is widely tested according to the German Institute of Normalization or “DIN” standard.  The harder the athletic floor (concrete or asphalt being the worst), the more prone participants are to overuse or repetition injuries.  

2. Impact Attenuation
For the sake of this discussion, impact attenuation refers to the impact of a part of an athlete’s body part (head, shoulder, back, elbows, hands, and knees) with the surface.  Athletic surfaces can be grouped into two general categories in how their measurements of impact attenuation (and to a lesser degree shock absorption) are determined: area elasticity and point elasticity. 

Area elasticity refers to how well the floor surface will deform and absorb energy over the area of the impact. For example, a concrete floor would transmit zero area elasticity, and a trampoline would transmit tremendous area elasticity. The resulting impact attenuation would be very low for concrete (all of the impact goes right back to the athlete’s body) and very high for a trampoline (the trampoline absorbs a substantial amount of the energy). 

Cushioned wood athletic floors, like those found in most school gyms in America, are area elastic. Most synthetic floors, namely those installed directly on concrete, are not very area elastic. Point elasticity refers to how well the floor absorbs and returns energy over a small area (“soft underfoot”). For floor safety, soft under head, elbow, and knee is more relevant. The challenge is that athletic surfaces need to be hard enough to dribble a ball, but soft enough to be safe for falls. Wood gymnasium floor are less point elastic than synthetic floors. The resulting impact attenuation for wood vs. synthetic floors is therefore very comparable. 

Currently, indoor sports floors are not rated by any standard in the measurement of impact attenuation. The church leader must therefore make their best decision based on the information provided. Shock absorbency ratings are a good comparative measure.  Additionally, the American Society of Testing and Materials (ASTM) has conducted studies on the impact attenuation of surfacing materials with playground equipment. This study more directly reflects fall impacts from playground equipment and is certainly not definitive for athletic floors, but it does bare some relevance. 

3. Surface Friction

Surface friction, often called the coefficient of friction or sliding coefficient, is used to measure a floor's ability to control the sliding of athletes on its surface. For an indoor sports floor, the surface friction must be high enough to prevent premature and uncontrollable sliding of athletes on its surface, but also low enough to permit sliding off an extreme force. 

Rotating and pivoting motions can create strain on an athlete’s joints unless the floor has the proper friction coefficients. The measurement is in Newtons, and the range for the proper range is .5N to .7N. To contrast the ranges, ice equates to .1N and fly paper is .9N.  Typically for wood floors, surface friction is a direct function of the finish on the surface.  For most types of synthetic floors, the measurement is higher. The maintenance of any of these floors is critical and can affect the measurements. This measurement is also tested according to the German Institute of Normalization or “DIN” standard. 

All three of these criteria should be carefully evaluated prior to the decision of choosing an athletic floor type.

Chris Wedge is Southern regional manager for Aacer Flooring, LLC, www.aacerflooring.com.

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