Papers of the Week

An estimated 1.6 to 3.8 million concussions occur in sport and recreational activities annually. A sport related concussion (SRC) is contemporarily defined as a traumatic brain injury induced by biomechanical forces. Symptoms of concussion are caused by the metabolic cascade that includes excitatory neurotransmitter release, abnormal ion fluxes, increased glucose metabolism, lactic acid accumulation, elevated cerebral blood flow, energy deficit, and inflammation. These changes in the brain are responsible for the hallmark symptoms of a concussion such as headache, nausea, loss of consciousness, and pressure in the head. Most concussions resolve within 2-4 weeks, but approximately 10-33% of individuals have persistent symptoms for months after the initial injury. An associated comorbidity following concussion is post-concussion syndrome (PCS). Clinical diagnostic criteria for PCS requires a history of brain injury and the presence of at least two symptoms for a minimum of four weeks. Having three of eight symptoms (headache, dizziness, fatigue, irritability, insomnia, concentration problems, memory difficulty, or intolerance of stress emotion or alcohol) for at least four weeks has also been identified as grounds for PCS classification. The mainstay of treatment for a SRC traditionally is rest followed by a stepwise return to learn, then physical activity, and finally return to sport. Time lost due to concussion is at least five days following symptom resolution when following best practices for full return to contact sports. Currently, prescribed rest in which patients avoid physical and cognitive activity is the most widely used intervention. Recent research indicates that strict rest longer than one to two days following a concussion does not improve outcomes and may potentially cause an increase in symptom reporting. The increase in symptom reporting especially in athletes after prescribed rest may be due to physical deconditioning and the development of secondary symptoms such as fatigue and reactive depression. Exercise in general has benefits for body composition, skeletal health, cardiorespiratory fitness, depression, anxiety, and academic achievement, and it also improves cognition through increased cerebral blood flow, oxygen extraction, brain metabolism, and neuroplasticity. Aerobic exercise conducted at subsymptom and submaximal intensities has been proposed as a potential intervention for the negative effects of inactivity following a concussion. Subsymptom aerobic exercise has been defined as aerobic exercise performed at an intensity and duration that does not exacerbate post-concussion symptoms. The American College of Sports Medicine defines submaximal exercise as aerobic activity occurring at 85% of the age adjusted maximum heart rate. These terms used by different authors often refer to similar exercise intensities, but they cannot be used interchangeably. Therefore, the purpose of this critically appraised topic is to examine the safety of varying aerobic exercise intensities in patients with a concussion. In appraising the safety of controlled aerobic activity in comparison to complete rest clinicians will be able to determine if physical activity can be implemented in the plan of care for patients with a concussion.