Drop-Jump Landing Varies With Baseline Neurocognition: Implications for Anterior Cruciate Ligament Injury Risk and Prevention.
Herman DC, Barth JT. Am J Sports Med. 2016 Sep;44(9):2347-53. doi: 10.1177/0363546516657338. Epub 2016 Jul 29.
Take Home Message: An athlete with low baseline neurocognitive scores is likely to produce knee movement patterns that are associated to anterior cruciate ligament (ACL) injury.
An athlete with a low neurocognitive test score or poor neuromuscular control is more likely to experience an anterior cruciate ligament (ACL) injury. During sport activity, an athlete may have altered visual processing, movement planning, and reaction time due to external stimuli. Neuromuscular screening protocols are used to identify at-risk individuals to implement injury prevention programs. It may be beneficial to know if neurocognitive testing, which many athletes complete, can also serve as an injury screening tool. If relationships exist between these tests, then commonly administered neurocognitive tests may be used to help identify athletes at-risk of injury. The authors aimed to determine if differences exist in neuromuscular landing performance during a challenging athletic task between athletes with high or low neurocognitive performance. A total of 123 recreational athletes were administered the Concussion Resolution Index (CRI) to identify 20 high performers and 17 low performers. The CRI comprised three indices that were used in the study: Simple Reaction Time, Complex Reaction Time, and Processing Speed. The authors defined high performers as athletes that scored above the 80th percentile in 1 index and no lower than the 60th percentile in the other two. The low performers were identified by as athletes that scored below the 40th percentile in one index and no higher than the 70th percentile in the other two or athletes who had two index scores below the 30th percentile. These participants then underwent an unanticipated jump landing task. The participants jumped forward off a 30-cm box onto a forceplate before jumping at maximum effort to a second target. The second target was either directly in front, 45 degrees to the left, or 45 degrees to the right. The arrow that prompted the second target was randomly presented 250 milliseconds before the initial landing. At initial landing, the low performers demonstrated higher peak proximal anterior tibial shear force, higher peak vertical ground-reaction force, a greater knee abduction angle, and a lower truck flexion angle.
Overall, the authors found neuromuscular patterns that are associated with ACL injury among healthy recreational athletes with low neurocognitive scores. The unanticipated landing task may be able to simulate sport competition by demanding fast cognitive processing to execute a desired function. The results of this study may provide neurocognitive characteristics about athletes who are at risk for a noncontact ACL injury. The relationship between neurocognitive scores and neuromuscular performance may help explain why an athlete is at greater risk for an injury during the first year after a concussion. However, these authors looked at the relationship between neurocognitive scores and neuromuscular performance and not actual risk of injury. Despite this limitation, this study offers evidence that commonly used neurocognitive tests may provide important information about a person’s risk of ACL injury. For patients returning back to sport activity, clinicians may be able to address these neuromuscular and neurocognitive concerns by providing dual-attention tasks. Dual tasks with cognitive (counting backwards from 100 by 7) and physical (ball toss during a single leg balance stance) tasks may offer a greater challenge to a patient by limiting direct focus on the rehabilitation task. Clinicians may also consider using computerized testing of reaction time and processing speed as an additional screening tool to identify individuals at a greater risk for injury.
Questions for Discussion: With computerized baseline concussion tests commonly being administered, should clinicians use reaction or processing scores as a screening tool for injury?
Written by: Stephan Bodkin
Reviewed by: Jeffrey Driban