What is Concussion?

  • Concussion is a type of traumatic brain injury (TBI)
  • It can be defined as a head injury with a brief loss of brain function which can cause physical, cognitive and emotional symptoms. Concussion can occur with or without loss of consciousness.
  • It occurs when the body or head receives an impact causing the brain to shake inside the skull. The impact damages and stretches the brain cells causing them to release chemicals that affects how the brain works.

What are the Symptoms?



  • In New Zealand it is estimated that up to 36,000 people suffer TBIs each year, of which 95% are mild.
  • About one in every 8-10 people will not seek medical assistance or report their TBI to ACC.
  • TBIs which are sustained by the general population are significantly uncounted because people with mild concussion do not always seek medical treatment.
  • ACC statistics show that nearly 14,000 people are treated for TBIs each year.
  • The cost of TBI-related claims was $83.5 million in the 2015 financial year.
  • The New Zealand Treasury has identified that TBIs are second only to stroke for their impacts on employment and income
  • The leading causes of TBI in New Zealand are falls, mechanical forces, driving-related accidents, and assaults
  • Just over 20% of all TBIs in New Zealand are sustained through sport-related activity.
  • ACC launched the Traumatic Brain Injury and Strategy Action Plan (2017-2021) which aims to improve the quality of life for New Zealanders by reducing the incidence, severity and impacts of TBIs.

What is the science behind a concussion?

Exercise Vs Rest?

For years the research into concussion has suggested that rest is the key factor in the initial stages of recovery. It was understood that concussions create a temporary energy deficit in the brain, therefore activity (physical or cognitive) which requires energy would, in theory, make the concussion worse. Therefore, the rest was thought to help the brain conserve energy and recover.

However new emerging research suggests that this advise maybe actually prolonging recovery.  Recent studies into this new theory found that light exercise may play an important role in the recovery of acute concussion and in the prevention of the development of prolonged concussion symptoms (PCS)

Another article published in the Paediatrics Journal in Dec 2018 supports the above theory and suggests that after a concussion, initial reductions in physical and cognitive activity can be beneficial to recovery, but prolonged restrictions on physical exertion or removal from school can have negative effects on recovery and symptoms. The article documents that the neurological symptoms of concussion are not related to the neural damage but involves a neurometabolic series of events.

The below diagram explains the neurological processes involved upon sustaining a concussion or there is a more detailed description below.

Explanation : A Biomechanical injury to the brain such as a rugby tackle occurs where there is either direct or indirect contact to the head. In response to a signal initiated at a dendrite (from the neurotransmitter glutamate) the sodium channels (Na+) open within the axon of the membrane. This depolarisation causes the neuronal activity to reduce. To try and restore homeostasis/ balance the sodium-potassium pumps (Na+-K+) become more active which depletes the energy supply of the cells (as this uses ATP and hyperglycolysis). Blood flow to the brain is reduced and coupled with an increased energy demand this leads to an energy crisis. To normalise the intracellular levels neurons store sodium in the mitochondria. However, this actually reduces the efficiency of oxygen production which in turn worsens the energy crisis. After the increased use of ATP and glucose for energy the hypometabolic state that has been created can last for up to 4 weeks. 

One of the largest studies on paediatric concussion found that people who engage in physical activity within the first week after injury were significantly less likely to suffer from symptoms beyond 4 weeks.  Additionally, researchers have also found that with each successive day that a patient waited to initiate exercise the more prolonged the recovery. The participants who started exercise earlier returned to school faster. The evidence from this study revealed that very light exercise, which include walks and light stationary bike, is safe and could speed up recovery.

What does this mean ?

There are limitations to the above studies, however, there is evidence that the old methods of rest in a dark room for days are not as beneficial as once thought. Very light exercise as stated above is recommended in the initial few days post sustaining a concussion.



Dixon, S. (2015). The Employment and Income Effects of Eight Chronic and Acute Health Conditions. New Zealand Treasury Working Paper 15/15. Wellington New Zealand Government.

Feigin, V. L., Theadom, A., Barker-Collo, S., Starkey, N., McPherson, K., Kahan, M., Ameratunga, S. (2013). Incidence of traumatic brain injury in New Zealand: a population-based study The Lancet Neurology, 12(1), 53-64. doi:10.1016/S1474-4422(12)70262-4.

Grool AM, Aglipay M, Momoli F, Meehan WP III, Freedman SB, Yeates KO, et al. Association Between Early Participation in Physical Activity Following Acute Concussion and Persistent Postconcussive Symptoms in Children and Adolescents. JAMA. 2016 Dec 20;316(23):2504.

Lawrence DW, Richards D, Comper P, Hutchison MG. Earlier time to aerobic exercise is associated with faster recovery following acute sport concussion. Janigro D, editor. PLoS ONE. 2018 Apr 18;13(4):e0196062.


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