Traumatic Brain Injury
It is estimated that approximately 1.6 to 3.8 million sports related traumatic brain injuries (TBI) occur every year, accounting for roughly 15% of all high school sport-related trauma reported. However, these numbers may be considered an underestimate due likely to failures in reporting of head injuries sustained or seeking medical attention. In fact, approximately 55% of pediatric athletes who sustained a concussion were not seen within a health care facility and approximately 42% of adults with a mild TBI (mTBI) did not seek medical care as well. The age group most vulnerable for sustaining a sports related concussion (SRC) is between ages 9-22 years old when team sports are most popular. Additionally, females have been diagnosed at higher rates of concussion susceptibility than males during both competition (1.46x) and practices (1.75x).
A TBI can be defined as a bump, blow, or jolt to the head or a penetrating head injury that leads to the disruption of normal brain function. The severity of this injury can be measured based on their Glasgow Coma Scale (GCS) score (Mild [13-15]; Moderate [9-12]; Severe [3-8]). A sport related concussion (SRC) is considered a form of mTBI and overlaps with a GCS score of 13-15.
According to the Concussion in Sport’s Group (CISG) 5th International Conference, the current definition of an SRC involves the following criteria:
- Direct or indirect trauma to any area of the body with an associated force transmitted to the head
- Rapid (seconds to minutes) or delayed (minutes to hours) symptom presentation, typically seen with spontaneous resolution
- Negative standard neuroimaging (computerized tomography [CT] or magnetic resonance imaging [MRI]) reflecting the appearance of a functional rather than structural injury of the brain
- Occurring with or without loss of consciousness and treated with a stepwise resolution of symptoms
A concussion should be treated as both structural and functional trauma to the brain. Structural damage includes the alterations in the structures of the brain related to concussion symptomology while functional damage is related to the changes in cellular and/or neuronal connections and functions that produce the concussive symptoms.
How do you prevent a traumatic brain injury?
Currently, experts agree that the prevention of incurring a mTBI during practice or competition is highly unlikely as no materials or action plans are available as supported by research-based evidence. At this point, the only way to completely prevent a TBI from occurring during sport would be not participating. However, the associated injuries and illnesses that may occur due to a general lack in exercise could lead to similarly detrimental implications regarding one’s health.
With this consideration in mind, the following include certain measures of prevention that have been proposed to minimize the risks of TBIs from occurring while focusing on the reduction of long-term risks of injury after SRC diagnosis.
Legislation and Education
By 2014, all 50 states and the District of Columbia had successfully passed youth concussion laws through their state-based legislative systems. These laws required all organizations involved in operating sports programs for youth athletes (<18 years old) to provide educational materials and programs to inform coaches, athletes, and parents about the nature and associated risks of concussions. These materials should be provided on an annual basis and all parties involved should acknowledge their participation and understanding of these concepts via signature. Furthermore, these mandated laws state that any athlete suspected of sustaining a concussion should be immediately removed from play and inhibited from returning to same-day and future activities without written medical clearance received from a health care provider properly trained in the evaluation and management of a concussion. It should be noted that variations in type of education provided, frequency of signed certification required, return-to-play content, and type of health care provider allowed to provide written clearance may vary from state to state. Previously conducted research has indicated that these laws have had a positive impact by increasing the amount of athletes reporting on symptoms present and a decrease in the amount of coaches allowing players to return to play while symptomatic.
Rule changes have been recently mandated and enforced by multiple governing officials in a variety of sports in an effort to reduce the amount of player-to-player collisions occurring within competitions and practices at a younger age. Additionally, officials have lobbied for a stricter enforcement of rules already in place to provide safer environments for athletes to compete in. Furthermore, coaches have begun to influence technique alterations in an effort to provide safer means of collisions between players when competing in compact sports. They have also encouraged their athletes to play by the rules enforced by officials while discouraging unnecessarily aggressive playing styles. All of these actions have been associated with measures taken to decrease the number and severity of concussions occurring within athletics.
Weaker neck muscles have been found to be a predictor of TBI occurrence due to their inability to reduce forces maintained from impact to the head. In fact, with each additional pound of strength obtained within the neck, athletes may see a resulting 5% reduction in risk of SRC during practice or competition. Therefore, a cervical muscle strengthening program has been recommended for athletes by some experts regarding concussion prevention. This improved neck strength along with the ability to anticipate and activate the neck musculature during impact has been associated with a reduction of kinematic impact to the head.
Mouthguards, helmets (and modifiers), and other forms of headgear have all been associated with a lack in evidence-based support for a benefit in use when considering concussion prevention. However, this equipment has established a role in the prevention of other head, face, and neck injuries that could occur during practice or competition in athletics.
Currently no evidence-based support is available for medicinal or supplemental use in the prevention of concussions. Acetaminophen and nonsteroidal anti-inflammatory (NSAIDs) medication has been most commonly recommended for treatment of certain symptoms associated with a concussion, but not in any preventative measure. Similarly, there are no current supplements available on the market that can effectively prevent a concussion from occurring. However, future usage may be possible as positive trials have been recorded within animal models.
What puts an individual at risk for traumatic brain injury?
Table 1 adapted from: Satarasinghe, P., Hamilton, D.K., Buchanan, R.J., & Koltz, M.T. (2019). Unifying pathophysiological explanations for sports-related concussion and concussion protocol management: literature review. Journal of Experimental Neuroscience, 13, 1-10.
|Potential Risk Factors for Sport Related Concussion (SRC)||Potential Consequences of Sport Related Concussion (SRC)|
|History of previous concussions||Onset of headaches|
|Participation in full/limited contact sports||Cognitive deficits|
|Position played in sport||Balance/coordination issues|
|Age||Neurodegenerative disease (Chronic Traumatic Encephalopathy [CTE])|
|Occurrence of migraines|
|Depression and other psychiatric disorders|
Diagnosing a concussion
The diagnosis of a concussion is a challenging process to complete and must be conducted by a licensed health care provider, such as an athletic trainer (ATC) trained in the clinical assessment of traumatic brain injury. This diagnosis may be helped even further by enlisting the services of someone familiar with the athlete in question to obtain more accurate identification of alterations in normal personality traits in order to judge deviations from baseline behaviors. Unfortunately, the process of diagnosing a concussion lacks assessments that have been constructively validated and are based on objectively-founded evidence. Additionally, initial reports are forced to rely on self-reported symptoms which can be troublesome if these symptoms may be caused by other common conditions.
If not already required, sports organizations should consider implementing mandatory preparticipation physical evaluations for all participating athletes before the upcoming season. These assessments should also include a medical history evaluation of traumatic brain injury history including the number incurred, recovery course of each, and time between each injury. Additionally, the presence of any other premorbid or comorbid conditions or modifiers which could make the diagnosis of a concussion more difficult should be identified. These may include a history of learning disorders or attention deficit disorders (ADD/ADHD), motion sickness or sensitivity, personal or family history of mood disorders or migraine/headache disorders, and information on current medication usage.
Some experts also suggest the use of baseline evaluations before sports participation to assist with diagnosis of traumatic brain injuries and decisions regarding an athlete’s ability to return to play after sustaining an SRC. The National Collegiate Athletic Association (NCAA) has recommended that these evaluations include a symptom checklist, cognitive evaluation, and balance assessment as best practice for this particular evaluation. However, these tests should not be repeated on an annual basis and are not considered a requirement for appropriate standard of care suitable for SRC management.
On Field/Sideline evaluation
“When in doubt, take them out!”
When an injury such as a TBI is suspected, it is recommended that this athlete be immediately removed from play and prohibited from returning to any activity at least within that same day even without a proper diagnosis. This process should be performed in a distraction-free environment where adequate time for examination and administration of all necessary concussion tests should be given for the licensed medical provider on staff.
During a sideline evaluation, the sports medicine clinician will obtain a brief history of the event and/or the athlete behavior along with evaluations of the athlete’s orientation, memory, concentration, balance, speech patterns, and how they seem to be processing information. Additionally, cervical palpations and range of motion assessments may be performed to assess for other concurrent injuries.
Signs and Symptomology
Table 2 adapted from: Harmon, K.G., et al. (2019). American Medical Society for Sports Medicine Position Statement on Concussion in Sport. Clinical Journal of Sports Medicine, 29, 87-100.
|Reasons for immediate removal and prompt evaluation||Concerns for more serious head injury activating emergency action plan (EAP)|
|Loss of Consciousness (LOC)||Prolonged LOC|
|Impact seizure||Severe/worsening headache|
|Tonic posturing||Repeated emesis|
|Gross motor instability||Declining mental status|
|Confusion||focal neurological deficit|
|Amnesia||Suspicion of significant cervical spine injury|
|Motor incoordination/balance problems|
A suspected concussion may include any of the above-mentioned points and the associated signs and symptoms of a concussion may include physical signs, behavioral alterations, cognitive impairment, and sleep disturbance resulting from mechanisms resulting from either player-to-player contact or equipment-to-player contact.
Research has found that 54.9% of athletes presenting with a diagnosed TBI have reported 5 or more symptoms upon evaluation with the most common symptoms including:
- Headaches (94.7%)
- Dizziness (74.8%)
- Difficulty concentrating (61.0%)
- Sensitivity to light (46.6%)
- Sensitivity to sound (39.3%)
Additionally, most symptoms have been reported as resolved most commonly within a period of 7 days (40.7%) or 2 weeks (21.7%). Furthermore, studies have shown that females have a greater association with symptomology lasting for a longer period of time than males. A more detailed list of signs and symptoms can be found below:
|Loss of Consciousness (LOC)||Balance issues/dizziness|
|Unequal pupil size||Diplopia|
|Slowness to answer questions||Trouble sleeping|
|Loss of balance||Trouble concentrating|
|Atypical behavior/personality changes||Memory issues|
|Nystagmus||Sensitivity to light or noise|
Available Evaluations for TBI Assessment
When considering a sideline evaluation, administrators must remember that there is no single, gold-standard test that exists and that all widely accepted tests for TBI assessment currently have questionable reliability standards possibly leading to high variability and a large number of errors during diagnosis. It is suggested that due to the multiple areas of SRC sign and symptomology that must be evaluated, the combination of multiple evaluation tools may be beneficial. These evaluation protocols may include:
- Sports Concussion Assessment Tool V5 (SCAT5)
- Available for children and adolescents/adults
- Modified Balance Error Scoring System (mBESS)
- Post-concussion Symptom Scale (PCSS)
- Vestibular/Ocular Motor Screening (VOMS)
Emergency room or other medical care facility
It would be ideal for an athlete who is suspected of incurring a TBI to be immediately tested by a sideline health care provider if available. However, we understand that these services may not always be accessible. Therefore, if first contact with an athlete suspected of suffering from a TBI is within an emergency room or other medical care facility, a comprehensive history and neurological examination should be conducted. This evaluation should include an assessment of medical history for the athlete, details of the injury mechanism, symptom trajectory, neurocognitive functioning, sleep disturbances, ocular and vestibular functionality, and an examination of any gait, balance, or cervical spine disturbances. Additionally, it would be important to assess for any structural injury if needed to rule out injuries to the cervical spine, skull fractures, or an intracranial hemorrhage.
What else could this be?
Always be aware of possibly premorbid or comorbid conditions that could be presented by the athlete during assessment for a TBI. Additionally, the following includes a list of possible other diagnoses that should be considered instead of or with an TBI diagnosis:
- Intracranial hemorrhage
- Subdural hematoma
- Epidural hematoma
- Skull Fracture
- Second impact syndrome
- Heat illness
- Drug overdose or interaction
How do you treat an individual with traumatic brain injury?
After a conclusive TBI diagnosis has been completed, the effected athlete should be provided at least 24 to 48 hours of both physical and cognitive symptom-limited rest before being gradually reintroduced to normal daily activities while staying below symptom-exacerbation thresholds. When considering this ‘prescribed rest’ period, ‘total rest’ or ‘cocoon therapy’ is no longer recommended due to possibly detrimental effects similarly seen with social isolation. Athletes should not be isolated to a dark room with prohibitions on electronic usage. Instead, rest periods should be in environments as tolerated by vestibular, ocular, cognitive, and physical signs and symptoms. Alterations such as limitations to electronic screen time, adjustments to brightness levels, or increasing font size may be necessary to reduce episodes of symptom exacerbation during rest. Athletes who are legally able to drive should also be discouraged from driving due to deficits in reaction time and judgement of road hazards. Above all else, remember that each athlete and their corresponding concussion is unique and must be treated as such!
Therapy and Collaborative Care
When considering the treatment of a TBI efforts made towards collaborative care regarding concurrent signs and symptoms may prove beneficial.
Vestibular therapy should focus on specific deficits identified by the clinician and use an ‘expose-recovery’ model towards vestibular rehabilitation.
Cognitive work should be limited or modified so that symptoms are not further exacerbated causing for elongated recovery measures.
Sleep hygiene may need to be addressed, monitored, and treated with nonpharmacologic and/or pharmacologic strategies.
Psychological symptoms, such as irritability, depression, and anxiety, should be evaluated and offered appropriate treatment when necessary.
Medicinal use, such as acetaminophen and nonsteroidal anti-inflammatory (NSAIDs), has been recommended by medical personnel after a concussion diagnosis to deal with certain symptomology. However, chronic use is discouraged and usage should be noted during diagnosis or serial evaluations due to possible masking of signs and symptoms.
When can the individual return to activity?
At the conclusion of the initial 48-hour window of symptom-limited rest, athletes should be encouraged to gradually pursue cognitive and physical activity while remaining below the symptom-exacerbation threshold.
When considering the recovery process for an athlete diagnosed with a TBI, a reasonable approach must be taken dependent on the symptomology presented. Athletes should be inhibited from returning to physical activity and competition to quickly due to the dangers of incurring a longer recovery period. Studies have shown that athletes who continued to play after an SRC diagnosis were approximately 9x more likely to have a recovery period longer than 21 days. Additionally, athletes who have been suspected of incurring an SRC sustained an additional head impact within 24 hours of the original injury, were found to have a greater symptom burden and longer recovery time period. However, negative consequences have also been associated with extremes of stricter restrictions during the recovery period from an SRC.
When considering a return to play protocol, each stage should be conducted over a time period of 24 hours and may last from 5-7 days without symptom exacerbation. If signs and symptoms return, the athlete should be immediately shut down from that particular stage and enter a rest period of 24 hours before resuming the stage they had previously began. However, it must be stressed that each athlete and their symptomology may react differently during the return to play protocol and appropriately individualized alterations may be required during rehabilitation. Studies have demonstrated a recovery period of one to four weeks for a majority of pediatric and adolescent athletes diagnosed with an SRC. For athletes that require a return to academia, students should receive academic adjustments to reduce workload and environmental triggers that may exacerbate symptoms. However, athletes should be successfully returned to academics before returning to sports.
The following is a general return to play protocol that may need to be individually adapted for each athlete diagnosed:
Table 4 adapted from: McCrory, P., et al. (2017). Consensus statement on concussion in sport- the 5(th) international conference on concussion in sport held in Berlin, October 2016. British Journal of Sports Medicine, 51, 838-847.
|Rehabilitation Stage||Functional Activity/Exercise|
|Stage 1: Prescribed rest||24-48 hours should be provided for symptom-limited rest|
|Stage 2a: Activity limited by symptoms
Stage 2b: Return to learning
|2a) Introduction of daily activities that are below symptom-exacerbation threshold
2b) Athlete should be fully returned to academic schedule if injury occurs during school year
|Stage 3: Light aerobic exercise of low intensity||Activity with elevation of heart rate above baseline (i.e. walking or cycling at leisurely pace)|
|Stage 4: Exercise specific to sport||Sport-specific movement with contact strictly avoided|
|Stage 5: Training without contact||Resuming sport-specific drills with goal of resuming proper coordination with continued avoidance of contact|
|Stage 6: Resumed full contact practice||Practicing in drills with included contact while closely monitoring for any symptom exacerbation|
|Stage 7: Full return to play||Resume all normal activities and participation in sport|
Harmon, K.G., et al. (2019). American Medical Society for Sports Medicine Position Statement on Concussion in Sport. Clinical Journal of Sports Medicine, 29, 87-100.
National Collegiate Athletic Association (NCAA). Interassociation Consensus: Diagnosis and Management of Sport-Related Concussion best Practices. Indianapolis, IN; 2016.
Patricios, J., et al. (2017). What are the critical elements of sideline screening that can be used to establish the diagnosis of concussion? A systematic review. British Journal of Sports Medicine, 51, 888-894.
Randolph, C., McCrea, M., and Barr, W.B. (2005). Is neuropsychological testing useful in the management of sport-related concussion? Journal of Athletic Training, 40, 139-152.
Echemendia, R.J., et al. (2017). The Sport Concussion Assessment Tool 5th Edition (SCAT5): background and rationale. British Journal of Sports Medicine, 51, 848-850.
Davis, G.A., et al. (2017). The Child Sport Concussion Assessment Tool 5th Edition (SCAT5): background and rationale. British Journal of Sports Medicine, 51, 859-861.
McCrory, P., et al. (2017). Consensus statement on concussion in sport- the 5(th) international conference on concussion in sport held in Berlin, October 2016. British Journal of Sports Medicine, 51, 838-847.
Collins, M.W., et al. (2016). Statements of agreement from the Targeted Evaluation and Active Management (TEAM) approaches to treating concussion meeting held in Pittsburgh, October 15-16, 2015. Neurosurgery, 79, 912-929.
Schneider, K.J., et al. (2013). The effects of rest and treatment following sport-related concussion: a systematic review of the literature. British Journal of Sports Medicine, 47, 304-307.
Hoffman, N.L., et al. (2017). Influence of postconussion sleep duration on concussion recovery in collegiate athletes. Clinical Journal of Sports Medicine. [epub ahead of print].
McCarty, C.A., et al. (2016). Collaborative care for adolescents with persistent postconcussive symptoms: a randomized trial. Pediatrics, 138, e20160459.
Hugentobler, J.A., et al. (2015). Physical therapy intervention strategies for patients with prolonged mild traumatic brain injury symptoms: a case series. International Journal of Sports Physical Therapy, 10, 676-689.
McKeithan, L., et al. (2019). Sport-related concussion: evaluation, treatment, and future directions. Medical Sciences, 7, 44-63.
Langlois, J.A., Rutland-Brown, W., & Wald, M.M. (2006). The epidemiology and impact of traumatic brain injury: A brief overview. Journal of Head Trauma Rehabilitation, 21, 375-378.
Kerrigan, J.M. & Giza, C.C. (2017). When in doubt, sit it out! Pediatric concussion-an update. Child’s Nervous System, 33, 1669-1675.
Starling, A.J., Leong, D.F., Bogle, J.M., & Vargas, B.B. (2016). Variability of the modified Balance Error Scoring System at baseline using objective and subjective balance measures. Concussion, 1, CNC5.
McAvoy, K., Eagan-Johnson, B., & Halstead, M. (2018). Return to learn: Transitioning to school and through ascending levels of academic support for students following a concussion. NeuroRehabilitation, 42, 325-330.
Facts about concussion and brain injury. Centers for Disease Control and Prevention. https://www.cdc.gov/traumaticbraininjury/pdf/Fact_Sheet_ConcussTBI-a.pdf. Published 2017.
Scopaz, K.A. & Hatzenbuehler, J.R. (2013). Risk modifiers for concussion and prolonged recovery. Sports Health, 5, 537-541.
Daneshvar, D.H., Nowinski, C.J., McKee, A., & Cantu, R.C. (2011). The epidemiology of sport-related concussion. Clinical Sports Medicine, 30, 1-17.
Satarasinghe, P., Hamilton, D.K., Buchanan, R.J., & Koltz, M.T. (2019). Unifying pathophysiological explanations for sports-related concussion and concussion protocol management: literature review. Journal of Experimental Neuroscience, 13, 1-10.
O’Connor, K.L., et al. (2017). Epidemiology of sport-related concussions in high school athletes: National Athletic Treatment, Injury and Outcomes Network (NATION), 2011-2012 through 2013-2014. Journal of Athletic Training, 52, 175-185.
Meehan III, W.P., d’Hemecourt, P., Collins, C.L., & Comstock, R.D. (2011). Assessment and management of sport-related concussions in United States high schools. American Journal of Sports Medicine, 39, 2304-2310.
LaRoche, A.A., Nelson, L.D., Connelly, P.K., Walter, K.D., & McCrea, M.A. (2016). Sport-related concussion reporting and state legislative effects. Clinical Journal of Sports Medicine, 26, 33-39.
Zemek, R.L., Farion, K.J., Sampson, M., & McGahern, C. (2013). Prognosticators of persistent symptoms following pediatric concussion: A systematic review. JAMA Pediatric, 167, 259-265.
Brett, B.L., Kuhn, A.W., Yengo-Kahn, A.M., Solomon, G.S., & Zuckerman, S.L. (2018). Risk factors associated with sustaining a sport-related concussion: An initial synthesis study of 12,320 student-athletes. Archives of Clinical Neuropsychology, 33, 984-992.
Halstead, M.E., Walter, K.D., & Moffatt, K. (2018). Sport-related concussion in children and adolescents. Pediatrics, 142, e20183074.
Collins, C.L., et al. (2014). Neck strength: A protective factor reducing risk for concussion in high school sports. Journal of Primary Prevention, 35, 309-319.
Giza, C.C. & Hovda, D.A. (2014). The new neurometabolic cascade of concussion. Neurosurgery, 75, S24-33.
Graham, R., Rivara, F.P., Ford, M.A., & Spicer, C.M., eds. (2014). Sports-Related Concussions in Youth: Improving the Science, Changing the Culture. Washington, DC: The National Academies Press.
Setnik, L. & Bazarian, J.J. (2007). The characteristics of patients who do not seek medical treatment for traumatic brain injury. Brain Injury, 21, 1-9.
Giola, G. & Collins, M. (2006). Centers for disease control and prevention. Acute Concussion Evaluation (ACE): physician/clinician office evaluation. Available at: https//www.cdc.gov/headsup/pdfs/providers/ace-a.pdf.
Elbin, R.J., et al. (2016). Removal from play after concussion and recovery time. Pediatrics, 138, e202160910.
Terwilliger, V.K., Pratson, L., Vaughan, C.G., & Gioia, G.A. (2016). Additional post-concussion impact exposure may affect recovery in adolescent athletes. Journal of Neurotrauma, 33, 213-223.
Sufrinko, A.M., et al. (2017). The effectiveness of prescribed rest depends on initial presentation after concussion. Journal of Pediatrics, 185, 167-172.
Leddy, J., Hinds, A., Sirica, D., & Willer, B. (2016). The role of controlled exercise in concussion management. PM&R, 8, S91-S100.
Halstead, M.E., McAvoy, K., Devore, C.D., Carl, R., Lee, M., & Logan, K. (2013). Council on Sports Medicine and Fitness; Council on School Health. Returning to learning following a concussion. Pediatrics, 132, 948-957.
Baker, A., Unsworth, C.A., & Lannin, N.A. (2015). Fitness-to-drive after mild traumatic brain injury: Mapping the time to trajectory of recovery in the acute stages post injury. Accident Analysis & Prevention, 79, 50-55.
Stache, S., Howell, D., & Meehan III, W.P. (2016). Concussion management practice patterns among sports medicine physicians. Clinical Journal of Sports Medicine, 26, 464-468.
Heyer, G.L. & Idris, S.A. (2014). Does analgesic overuse contribute to chronic post-traumatic headaches in adolescent concussion patients? Pediatric Neurology, 48, 1294-1298.
Nelson, L.D., et al. (2016). Age differences in recovery after sport-related concussion: A comparison of high school and collegiate athletes. Journal of Athletic Training, 51, 142-152.
Boden, B.P, Tacchetti, R.L., Cantu, R.C., Knowles, S.B., & Mueller, F.O. (200). Catastrophic head injuries in high school and college football players. American Journal of Sports Medicine, 35, 1075-1081.
DiFazio, M., Silverberg, N.D., Kirkwood, M.W., Bernier, R., & Iverson, G.L. (2016). Prolonged activity restriction after concussion: Are we worsening outcomes? Clinical Pediatrics (Philadelphia), 55, 443-451.
Green, L. (2014). National Federation of State High School Associations. Legal perspectives, recommendations, on state concussion laws. Available at https:/www.nfhs.org/articles/legal-perspectives-recommendations-on-state-concussion-laws/.
Concannon, L.G. (2016). Effects of legislation on sports-related concussion. Physical Medicine and Rehabilitation Clinics of North America, 27, 513-527.
Wisniewski, J.F., Guskiewicz, K., Trope, M., & Sigurdsson, A. (2004). Incidence of cerebral concussions associated with type of mouthguard used in college football. Dental Traumatology, 20, 143-149.
McGuine, T.A., Hetzel, S., McCrea, M., & Brooks, M.A. (2014). Protective equipment and player characteristics associated with the incidence of sport-related concussion in high school football players: A multifactorial prospective study. American Journal of Sports Medicine, 42, 1224-1229.
Mihalik, J.P., Lynall, R.C., Wasserman, E.B., Guskiewicz, K.M., & Marshall, S.W. (2017). Evaluating the “Threshold theory”: Can head impact indicators help? Medicine & Science in Sports & Exercise, 49, 247-253.
Elbin, R.J., Beatty, A., Covassin, T., Schatz, P., Hydeman, A., & Kontos, A.P. (2015). A preliminary examination of neurocognitive performance and symptoms following a bout of soccer heading in athletes wearing protective soccer headbands. Research in Sports Medicine, 23, 203-214.
McIntosh, A.S., McCrory, P., Finch, C.F., Best, J.P., Chalmers, D.J., & Wolfe, R. (2009). Does padded headgear prevent head injury in rugby union football? Medicine & Science in Sports & Exercise, 41, 306-313.
Reisner, A., et al. (2017). Quality improvement in concussion care: Influence of guideline-based education. Journal of Pediatrics, 184, 26-31.
Ashbaugh, A. & McGrew, C. (2016). The role of nutritional supplements in sports concussion treatment. Current Sports Medicine Reports, 15, 16-19.
Eckner, J.T., Oh, Y.K., Joshi, M.S., Richardson, J.K., & Ashton-Miller, J.A. (2014). Effect of neck muscle strength and anticipatory cervical muscle activation on the kinematic response of the head to impulsive loads. American Journal of Sports Medicine, 42, 566-576.