| Jul 06, 2015
By Li-Shan Chou, Ph.D.
The relative re-injury risk for individuals who have sustained a concussion has been reported to be almost six times greater than those with no history of concussion. However, the factors, which contribute to this increased risk, are not clearly understood. Hence, the clinical decision of when to allow individuals to return to pre-injury levels of activity remains among the most difficult decisions in sports medicine.
Previous research has reported that student athletes with concussion may experience a worsening of symptoms if they return to sports or school prematurely. Therefore, proper timing of activity resumption after a concussion is of critical importance to reduce the risk of prolonging the course of recovery. As deficits in physiologic functions have been documented to persist beyond patient-reported recovery of symptoms, additional objective measurements may be assistive in determining full recovery of the brain after injury.
The ability to effectively execute motor tasks under conditions of divided attention (dual-task) is an important element for successful sport performance. Of particular interest to our research, this ability has been shown to be particularly sensitive to a concussion and remains impaired for several weeks after injury. In our April 2015 MSSEarticle
, we addressed the questions of how return-to-activity (RTA) affects the recovery of single and dual-task gait balance control as well as recovery of cognitive functions and clinical symptoms. We employed a dual-task gait paradigm, which involved a recorded voice played over speakers. The voice expressed the words “high” or “low,” at pitches that were occasionally inconsistent with the meaning of the word (e.g., a low-pitched voice might say the word “high”). The subject, while walking, was required to identify the correct pitch, regardless of the word that was heard. In a prospective-longitudinal study, we followed 19 concussed high school students over a period of two months post-injury and measured these variables in the acute post-injury period (within 72 hours of injury) and at systematic intervals thereafter (one week, two weeks, one month, two months post-injury) against 19 uninjured matched controls. To test the effect of activity resumption within this two-month testing period, we examined the recovery trajectory of the variables immediately prior to and immediately after RTA clearance for each concussed subject. The results revealed improvement in dual-task gait medial-lateral balance control during the period immediately prior to RTA, but a worsening immediately after RTA. All other variables showed improvement in the pre-RTA period, and these continued to improve or remain stable post-RTA. This study concurs with findings from our group
reported previously in MSSE, which showed a recovery reversal in side-to-side stability when walking with a divided attention following RTA in concussed college-age students.
The finding that regression of recovery was only observed in dual-task gait balance control immediately following the clearance for activity resumption, but not in cognitive, symptom or single-task walking variables suggests that dual-task medial-lateral sway is particularly sensitive to a concussion and its recovery may be influenced by premature RTA. This study also suggests that examination of dual-task gait stability may be able to detect important residual concussion-related impairments after cognitive and symptom resolution. Moreover, these findings reinforce the need for a multifaceted approach to concussion management. Viewpoints presented on the SMB blog reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.
Li-Shan Chou, Ph.D., is a professor and department head in the Department of Human Physiology at the University of Oregon. He directs the Motion Analysis Laboratory, and his research falls under general areas related to biomechanics and motor control of human movement, with focuses on the investigation of mobility impairments associated with ageing, musculoskeletal diseases or injuries and traumatic brain injury.
This commentary presents Dr. Chou’s views on the topic of a research article which he and his colleagues published in the April 2015 issue of
Medicine & Science in Sports & Exercise®