An Introduction to Concussions

Dr. Jill Murphy, DPT, LAT, CSCS

Concussions. Few words in sports medicine bring so many thoughts to mind, from professional sports heroes to protecting your very own little soccer or football player from a serious head injury. The media is all over it, and why wouldn’t they be, with NFL athletes choosing to forego millions of dollars by retiring early to avoid permanent brain damage? This article series will shed light on true details about concussions, from the frequency, risk by sport, prevention, diagnosis, and treatment. The facts presented here have been published in the latest sports medicine research journals; you won’t find any hype here. With solid information, you can quell any fears and draw your own opinions to make tough decisions based on accurate knowledge surrounding concussion risk and sports participation.

Concussion is a trauma-induced alteration in mental status whether or not the individual loses consciousness. It is categorized as a mild traumatic brain injury (TBI) that can range in severity from mild to very severe. Diagnosing concussion is a bit more difficult than defining it, because while there are tests to quantify symptom severity and functional loss, we cannot image the brain to determine the severity of a concussion once it occurs. Unless there is active bleeding in or around the brain, which only occurs as a result of the most severe concussions, imaging studies such as CT scans are typically negative. However, this does not mean that a concussion did not occur. At this time we simply do not have a way to image or a laboratory test able to capture the cascade of physiological changes that occur immediately following a concussion which are responsible for the functional losses associated with concussions.

These functional losses can be categorized into various symptom categories including mental, emotional, physical, coordination/balance, and visual changes that reflect the extent of neurologic injury. The symptoms typically come on immediately or within one hour of the original injury, but some issues might not be noticed until the days and weeks that follow. Concussion signs and symptoms may include one or all of the following: headache, nausea, vomiting, dizziness, fogginess, lightheadedness, light sensitivity, double vision, change in vision, tinnitus (ringing in the ears), slurred speech, memory loss, disorientation, confusion, loss of appetite, depressed mood, fatigue, sleeping more than usual, insomnia (not able to fall asleep or stay asleep), becoming more emotional than usual, dyscoordination, loss of balance, seizures, numbness or tingling, changes in behavior, slowed thinking, difficulty reading, and difficulty focusing and concentrating to study and/or take tests.

According to the CDC, the number of annual concussions in the US from recreational and formal sports participation is 3.8 million. The real number of concussions is likely to be much higher, because not all concussions are reported and formally evaluated by a medical professional. The 3.8 million concussions do not include head injuries occurring annually outside of sports. Any time a head is hit by a hard object in a forceful way, or anytime a head hits a hard object, the brain that is floating in fluid inside the skull is jostled, banging against the sides of the interior of the skull, complete with sharp prominences that can injure the brain. A whiplash effect from rapid acceleration followed by deceleration can also injure the brain and nerve fibers from direct impact, and even indirectly as the brain sloshes forward and back. Common head injuries that occur outside of sports participation are related to slips and falls that involve the head hitting a hard surface in toddlers, kids, and older adults, bomb blasts during military service, workplace mishaps, motor vehicle accidents, assaults, and injuries to kids engaged in free play. Because concussion risk is cumulative with each concussion sustained, it is important to note a child or athlete’s complete concussion history, not just the head injuries they may have incurred while participating in sports.

The number of concussions treated in US emergency departments from 2001 to 2009 increased by 62%. This increased awareness has driven more research into all aspects of concussion prevention and management. While football has the highest number of reported traumatic brain injuries, it also has the highest number of high school and collegiate participants than any other sport. Football is not the only sport where kids have an elevated concussion risk. Hockey, in contrast to football, has one of the lowest numbers of overall participants in the US, yet has one of the highest rates of concussions. Other contact and collision sports such as soccer, basketball, as well as other formal athletic participation in gymnastics, skiing and snowboarding, and even cheerleading place kids at a higher risk of concussion.

Please note that epidemiological data varies widely over time due to changes in reporting standards and lack of reported concussions in older data, so the data below is listed in terms of incidence of injury per athlete exposures, versus the total number of concussions sustained annually. Also of interest to note in the football data is that even though the practice rate of injury is much less than the game rate, because there are far more practices than games, more concussions are sustained in practice. This offers an opportunity to reduce concussion risk by reducing contact during football practice, a theory that has been validated by a recent research study conducted right here in Wisconsin.

The risk of getting a concussion due to sports participation is listed in the table below by sport and gender. These data are based on typical practice and game participation without alterations or limitations in contact.

High School Concussion Epidemiology (2005-06 Season)

Injury rate per 1,000 athlete exposures (defined as one athlete playing in one game or practice)
Volleyball  .05.05
Softball  .09.04
High School data provided by the High School Sports-Related Injury Surveillance System
Data from Gessel LM, Fields SK, Collins CL, Dick RW, Comstock RD. Concussions among United States high school and collegiate athletes. J 
Athl Train. Oct-Dec 2007;42(4):495-503.


The NCAA athlete’s concussion incidence is listed in the table below by sport and gender. Again this data is from normal practice and game participation without alterations to help prevent concussion such as limited contact practices.

Collegiate Concussion Epidemiology (2005-06 Season)

Injury rate per 1,000 athlete exposures (defined as one athlete playing in one game or practice)
Volleyball  .21.13
Collegiate data provided by the National Collegiate Athletic Association Injury Surveillance System 
Data from Gessel LM, Fields SK, Collins CL, Dick RW, Comstock RD. Concussions among United States high school and collegiate athletes. J 
Athl Train. Oct-Dec 2007;42(4):495-503. 


Collegiate Concussion Epidemiology (1998-2004 Seasons)

Injury rate per 1,000 hrs of athlete exposures
*Data collection for women's ice hockey began in 2000-2001.
Data from Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15 sports: summary and recommendations for 
injury prevention initiatives. J Athl Train. Apr-Jun 2007;42(2):311-319. 


Clearly concussions are a problem for many popular sports in the US and deserve increased attention to find ways to decrease the frequency and intensity of these mild traumatic brain injuries. The good news is that the injury rate in youth sports such as football are lower than that of older and more experienced high school and collegiate athletes due to the lower velocity and power of young football players. Other rule changes such as no headers in youth soccer also help reduce injury risk.

Upcoming articles in this series will further break down concussion risk by sport, gender, and position, in addition to addressing concussion assessment and diagnosis, treatment, and specific methods to prevent concussions that are supported by sports medicine research. If you have any questions about concussions or the specialized concussion rehabilitation MotionWorks has available for athletes with lingering symptoms from concussions including headaches and neck pain, nausea, vision changes, balance issues, and difficulty with returning to school and test taking, please contact our concussion specialist physical therapist and licensed athletic trainer, Dr. Jill Murphy, at or call us at 920-215-2050.

Click here for a PDF from the NATA on concussion symptoms and red flags:

Want additional resources for your school or team? Check out the CDC website for Heads Up for concussion resources at