The Potential for Brain Injury on Selected Surfaces Used by Cheerleaders
by Brenda J. Shields, MS1 and Gary A. Smith, MD, DrPH
J Athl Train. 2009 Nov-Dec; 44(6): 595–602.
from the Journal of Athletic Training 2009;44(6):595-602
This is the first study to investigate the potential for brain injury on selected surfaces used by cheerleaders, employing a method used to measure the impact attenuation of surface systems under and around playground equipment.16 Cheerleading-related falls from 15 and 20 ft (4.57 and 6.10 m) have been reported.14,27 Brain injuries, and even death, have resulted from cheerleading-related falls.14 In 2006, a collegiate cheerleader fell 15 ft (4.57 m) from a pyramid, landed on her head on a wood gym floor during a time-out performance for a basketball game, and sustained a chipped neck vertebra and a concussion.28 In our study, the critical height for a wood gym floor was 4.5 ft (1.37 m). Based on our data, we believe the cheerleader should not have been performing this type of maneuver on a wood floor.
Falls onto an impact-absorbing surface are less likely to cause a serious injury than are falls onto a hard surface, and the potential for life-threatening head impact injuries can be minimized by increasing the shock-absorbing capacity of the surface, decreasing the height from which the person falls, or both.16 Bare earth, grass, asphalt, and concrete are categorized as non–impact-absorbing surfaces,6 yet Hutchinson29 recommended that cheerleaders practice on grass rather than a hard gym floor. We found that the critical height for dry grass ranged from 3.5 to 4.5 ft (1.07–1.37 m), which is comparable with the 4.5 ft (1.37 m) for a wood gym floor (hard gym floor). Based on our data using critical height as an indicator of the impact-absorbing capacity of the surface, grass is not more impact absorbing than a wood gym floor. Therefore, the above-mentioned recommendation by Hutchinson29 would not be expected to improve cheerleading safety.
Many variables can affect the impact-absorbing capacity of a surface. Examples include temperature, moisture, age of the surfacing material, and thickness of the surfacing material. We demonstrated that the height of the grass and the moisture content of the soil can affect the impact-absorbing capacity of a grass surface. In cold temperatures, the resiliency of some surfaces may decrease, thus decreasing the impact-absorbing capacity of the surface. Temperature changes may also affect moisture retention by surfaces such as soil and grass, thereby altering the impact-absorbing capacity of these surfaces.
The American Association of Cheer-leading Coaches and Administrators30,31 created rules for cheer-leading safety that address the types of surfaces that are appropriate for cheer-leading and that limit the height of pyramid formations and partner stunts. The rules for collegiate cheerleaders state that “technical skills should not be performed on concrete, asphalt, wet or uneven surfaces, or surfaces with obstructions.”31 All pyramids and partner stunts are limited to 2 persons high for high school cheerleaders30 and 2 1/2 body lengths for pyramids formed by collegiate cheerleaders.31 Basket and elevator or sponge tosses and similar multibase tosses are prohibited on surfaces other than grass (real or artificial), a mat, or rubberized track,30,31 and pyramids of 2 1/2 body lengths are prohibited on surfaces other than grass (real or artificial) or a mat.31 Based on the results of the present study, we believe that some of these rules should be revised. The critical heights reported in our study for artificial turf, grass, a 4-in (0.10-m)–thick landing mat on a vinyl tile floor, and a rubberized track are all lower than the heights that are achieved during cheer-leading tosses and pyramids of 2 and 2 1/2 body lengths. Therefore, performing these maneuvers over these surfaces could place cheerleaders at risk for serious brain injury in the event of a fall. In our study, only the spring floor and a landing mat placed on a traditional foam floor were suitable for performing these maneuvers.
Data from our companion study32 illustrate the potential effectiveness of using our findings to help prevent brain injuries among cheerleaders. All the concussions reported in that study were sustained by cheerleaders who fell from higher heights than the critical heights reported in the present study for the surfaces on which they landed. These falls included a 6-ft (1.83-m) fall onto grass while performing a single-based stunt; a 5-ft (1.52-m) fall onto a wood floor while performing a single-leg stunt; a 5.5-ft (1.68-m) fall onto grass while performing a single-leg stunt; and a 6-ft fall onto artificial turf while performing a transition. It is customary to report fall heights as the distance between the surface the person was standing on before the fall and the surface the person landed on during the fall. This was the case for these 4 injury event descriptions. Therefore, the fall heights of the cheerleaders’ heads in these 4 cases were actually greater than the fall heights reported. In other studies, fall height may be defined as the difference in the positions of the person’s center of gravity at the start and end of the fall. Further research is needed to determine if these findings can be replicated with a larger sample size and among different populations of cheerleaders.
It is important to note that the critical heights we report in this study assume an unobstructed, vertical fall, in which the primary impact with the surface is made by the head. In some cases, a cheerleader may land on another cheerleader (spotter or base) during the fall, thus decreasing the deceleration of the head when it strikes the surface. It is also possible that another part of the body makes the primary impact with the surface and that the head makes a secondary impact. In this case, head deceleration upon impact is also reduced. Therefore, the critical height for each surface reported in our study represents a conservative estimate of the height at or below which a serious head impact injury from a fall is unlikely to occur on that surface.
Somehow, we do not associate concussions with cheerleaders, yet when you think of those giant people pyramids made out of stacked people, especially those at the top of the heap the height differences to the ground are high, as much as twenty feet if someone at the top falls. The other very scary aspect is that head contact with the regular practice floors typically like a gymnasium only require anything over four an a half feet before serious potential concussion can happen. This is not a big height difference at all.
So for you cheerleaders out there you should always practice on cushioned mats especially if you are doing athletic stunts over four and one half feet. Also here’s another suggestion: maybe have a Judo expert teach everyone how to roll-fall to dissipate energy away from the head onto the torso.