Fifteen minutes of high intensity running can impair performance on concussion testing; Implications for on-field diagnosis in sport

Objectives: To examine the effects of 15 min of high intensity treadmill running on concussion testing assessed by the King-Devick test. Design: Prospective Cohort Study. Methods: Participants self-selected to either a running or a control group. At baseline both groups were assessed using the King-Devick concussion test. The running group then completed 15-minutes of treadmill running at rating of perceived exertion of 7–9/10 while the control group sat quietly. Both groups repeated the King-Devick test following that 15-minute period. Results: Participants (n = 84 men, 53 women) were divided in two groups; running or control. Both groups, on average, had significant improvement after 15 min (suggesting a learning effect). Comparisons between the baseline and re-assessment scores indicated impaired performance was more common following high intensity treadmill running (n = 23 participants, 34.3%) compared to the control group (n = 10 participants, 14.3%, p = 0.006, OR = 3.44 [95%CI 1.40–8.50]). Four participants in the running group worsened their score at reassessment by more than 3 s compared to no participants in the control group. Conclusions: After 15 min of high intensity treadmill running, 1 in 3 participants scored a slower time at follow-up or committed a mistake compared to baseline. Implications for clinical practise include: the recommendation that baseline tests be conducted at rest and after high intensity exercise to provide accurate comparisons to assist in clinical decision making; and a cut-off of > 3 s may be a clinically useful difference between resting baseline and re-assessment using the King-Devick test.