Lower Extremity Stiffness Changes after Concussion in Collegiate Football Players
Dubose DF., Herman DC., Jones DL., Tillman SM., Clugston JR., Pass A., Hernandez JA., Vasilopoulos T., Horodyski M., Chielewski TL. Medicine & Science in Sport & Exercise. 2016; 49(1):167-172.
Take Home Message: An athlete with a recent concussion has altered lower extremity stiffness at the leg, hip, and knee, which could increase their risk for musculoskeletal injury.
Even when an athlete meets concussion return-to-play criteria they may be at an increased risk for musculoskeletal injury. This may be due to unresolved neuromuscular impairments, which can affect lower extremity stiffness. However, few researchers have looked at the effect of concussion on lower extremity stiffness. Therefore, the authors compared pre- to post-season changes in stiffness during a jump-landing task in a cohort of 39 Division I football athletes (13 with a history of concussion and 26 matched [age, position, season] controls with no history of concussions]). All athletes completed a jump-landing task starting with the left leg. The jump-landing task consisted of hopping off a 25 cm step with hands on hips and eyes facing forward. A test trial was successful if the athlete made solid foot contact with force plate and maintained balance on test leg for 3 seconds. Testing was repeated until a successful trial was obtained, and then repeated with the right leg. Then, the authors calculated leg, hip, knee, and ankle stiffness. Concussed athletes completed the post-season jump-task test ~50 days after the concussion. The authors found no differences between preseason or postseason values for hip, knee, ankle, and leg stiffness between groups. However, when the authors compared change in stiffness from preseason to postseason they found that the concussed athletes exhibited decreased stiffness at the leg and knee, and increased hip stiffness compared with the non-concussed athletes. There was no difference between groups for change in ankle stiffness.
The authors demonstrated that concussed athletes have altered lower extremity stiffness from pre- to post-season when compared with non-concussed athletes. Specifically, leg and knee stiffness decreased and hip stiffness increased in the concussed athletes. The authors suggest that stiffness in the lower extremity is controlled by the neuromuscular system, and this data provides further evidence of neuromuscular dysfunction after return to play from concussion. These changes in lower extremity stiffness could alter how an athlete lands, runs, and performs other movement patterns, which places them at risk for a musculoskeletal injury. Medical professionals should be aware of these changes in stiffness within the lower extremity. Additionally, clinicians need to recognize that an athlete is at greater risk for lower extremity injury after a concussion, and therefore should consider whether return to play guidelines need to be improved to include a high demand neuromuscular task. Lastly, medical professionals may need to consider implementing neuromuscular tasks in the concussion rehabilitation protocol to reduce the risk of subsequent injuries following a concussion.
Question for Discussion: Do you perform any neuromuscular tasks prior to releasing an athlete to full return to play? What type of tasks do you think should be incorporated into a concussion return to play protocol?
Written by: Jane McDevitt, PhD
Reviewed by: Jeff Driban
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