Should athletes continue to play after a concussion?

Why athletes should not continue to play after a concussion

The majority of athletes continue to play after a concussion because they do not tell their trainers how they feel. Kay 2014, found that more than half of concussions sustained during athletic competition are never reported. Furthermore, trainers and coaches do not know the signs and symptoms of a concussion.


One study found that high school and collegiate athletic trainers estimated that 5% of their football players sustained a concussion during the season. When the same athletes were asked how many of them had a concussion that year, 50% felt they had sustained a concussion.

The purpose of this article is not to cover sideline concussion management or the signs and symptoms of a concussion. For more information check out our article on the NFL sideline concussion management. This article is going to address the consequences of athletes who remain in a game after sustaining a concussion.

It may seem ridiculous that any athlete would continue playing after sustaining a suspected concussion. However, based on personal experience, the first thing an athlete does when they have a concussion is say “I’m fine”. Followed by, “I can play”. In fact, until recently professional athletes were allowed to remain in a game after sustaining a concussion.

NHL, NFL and the 1997 American Academy of Neurology Guidelines

Until 2013, the NHL/NFL used the 1997 American Academy of Neurology (AAN) guidelines for returning to play following a concussion. AAN guidelines state an athlete can return to play in the same game if they suffered a grade 1 concussion. It should be noted that there’s no longer a grading system for concussions. AAN guidelines classified a grade 1 concussion as consisting of transient confusion, no loss of consciousness. Also symptoms or mental status abnormalities that resolve in less than 15 minutes. If an athlete had a normal sideline assessment at rest, then they would be physically exerted. This consisted of a 40-yard sprint, 5 push-ups, 5 sit-ups, 5 knee bends. If an athlete could perform these maneuvers then they were permitted to return to play (Broshek et al., 2012).

In 2013, the AAN changed their recommendations to align their guidelines with the concussion in sport, 2012 Zurich consensus statement. The 2012 consensus statement and current AAN guidelines state, “any athlete suspected of experiencing a concussion immediately be removed from play”.

So what is the reason for the change in the recommendations and does the literature support this?

What is a concussion?

ConcussionA concussion is an energy deficit injury, as energy production (ATP) in the brain (mitochondria) is reduced by approximately 20%. This energy deficit causes a build up of reactive oxidative species (ROS) [think lactate acid after working out]. Accumulation of ROS can damage the nerve cells in the brain.

Continue to play after a concussion and body temperature

A study by Miyauchi et al., 2013, found that rats whose body temperature was immediately cooled following a concussion (hypothermic 35°C) had significantly improved cerebral blood flow and significantly reduced oxidative axonal damaged (damage to nerves by ROS), compared to a normal population (normothermic 37°C).

Furthermore, Titus et al., 2014, found that rats whose bodies were hyperthermic (39°C) 15 minutes prior to and 4 hours after a concussion were found to have significant impairment on long-term cognitive measures. However, rats that were injured in a hyperthermic state and then immediately cooled for 15 minutes, demonstrated no significant long-term cognitive deficits (similar to normothermic population).

These studies stress the importance of removing an athlete from competition after a suspected concussion and reducing their body temperature. Athletes should also be encouraged to sit in the shade or apply ice packs to the back of their neck immediately after a concussion to further reduce their body temperature.

Continue to play after a concussion and blood flow impairment

continue to play after a concussion and bloodflow

Animal models have shown as much as a 50% decrease in cerebral blood flow following a concussion. Although the evidence on blood flow impairments and concussions in humans is limited, there are a couple studies that have demonstrated profound effects. Following a concussion, advanced imaging (NIRS) has demonstrated that oxygen saturation in the brain decreased by 35 and persisted for up to a week. Further research has demonstrated that systemic oxygen saturation decreased by 20% during post-injury exercise on day 1 (Len et al., 2010).

Therefore, individuals who remain in a game after sustaining a concussion are putting their health at risk. This is because the brain already has reduced energy levels and high amounts of ROS. The addition of blood flow impairments only compounds this issue further.

Continue to play after a concussion and Impact testing (Neuropyschological) results

A study by Lovell et., 2004 investigated high school and collegiate athletes that suffered a concussion and their performance on neuropsychological testing (impact). The researchers compared the athlete’s baseline impact test score to post-injury scores immediately after a suspected concussion and then again at 36 and 72 hours later. The researchers found that 15 minutes after sustaining a concussion the athletes were asymptomatic and passed their baseline impact scores. However, the same athletes failed their baseline impact scores at 36 and 72 hours, and their symptoms continued to increase.

Coaches and trainers need to be taught that an athlete’s symptoms and cognitive performance immediately following a concussion is not a reliable method of determining whether or not they should be allowed to return to the same game.

Continue to play after a concussion and the effect on secretion of brain healing proteins

Brain-derived neurotrophic factor (BDNF) is essential to the maintenance of existing neurons, as well as promoting the growth of new neurons and synapses. Specifically, BDNF has been shown to decrease neurodegeneration, and increase neuroplasticity (Aguiar et al., 2011).

In the brain, BDNF is active in areas related to learning, memory and higher thinking. BDNF has been shown to be important in the formation of long-term memories (Bekinschtein P, et al., 2008). BDNF has also been shown to decrease anxiety and depression, and decreased levels have been associated with depression (Duman and Monteggia, 2006Martinowich et al., 2007).

In normal/healthy individuals, exercise promotes the synthesis and release of BDNF (Aguiar et al., 2011). Exercise immediately follow a concussion has shown to decrease BDNF, which correlates with impaired performance on cognitive memory tasks. Researchers have found that BDNF is decreased for approximately a week following a concussion. However, BDNF can be suppressed up to 3 weeks depending on the severity of injury (Griesbach GS,et al., 2004).

Therefore, athletes who continue to play after sustaining a concussion decrease the release of BDNF. This corresponds with the increased anxiety/depression and decreased cognitive performance experienced by some individuals after a concussion.

Continue to play after a concussion and recovery time

Should athletes continue to play after a concussionElbin et al., 2016, found athletes who continued to play after a concussion were almost 9 times more likely to have a prolonged recovery. A prolonged recovery defined as longer than 3 weeks of symptoms. Studies have shown the majority of concussed individuals will be symptom-free around 7-10 days; with only 10-15% of all concussions progressing to post-concussion syndrome. Therefore, research suggests athletes who continue to play following a concussion a far more likely to develop post-concussion syndrome.

This is important information for athletes, coaches and parents as research shows that continuing to play after a concussion not only exposes the brain to further harm. The athlete will also miss more playing as a result of staying in the game.

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