Sports Medicine Research: In the Lab & In the Field: Alterations in Leg Stiffness Following A Concussion May Lead to Changes in Return-to-Play Protocol (Sports Med Res)


Wednesday, January 18, 2017

Alterations in Leg Stiffness Following A Concussion May Lead to Changes in Return-to-Play Protocol

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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Dubose DF, Herman DC, Jones DL, Tillman SM, Clugston JR, Pass A, Hernandez JA, Vasilopoulos T, Horodyski M, & Chmielewski TL (2017). Lower Extremity Stiffness Changes after Concussion in Collegiate Football Players. Medicine and science in sports and exercise, 49 (1), 167-172 PMID: 27501359


Brooke Daniell said...

This study was an interesting read. I think this study shows yet another set of evidence for neuromuscular changes following a concussion. It is very interesting, yet not surprising, that increased chance for lower extremity injury is associated with a recent concussion. Because the results of this study found differences in leg, knee, and hip stiffness, but not in ankle, I wonder if that could have something to do with the exclusion criteria. They mentioned that they ruled out any LE injury that would be preventing the athlete from participating in sport. From what I understand, this means that an athlete with chronic ankle instability (that is still participating in a sport) wouldn't have been excluded from this study. CAI is actually quite common in collegiate athletes, so I would think it may have somewhat of an impact. It caused me to wonder if maybe the ankle results were confounded, due to the fact that CAI athletes already have neuromuscular changes in their ankles- even without a concussion. So, there may have actually been ankle stiffness changes with concussion, but they were somewhat masked by the changes in stiffness already present from previous ankle sprains or CAI in the unconcussed population. The previous idea may be a stretch, but it did spark my curiosity. Regardless, I think this study was well constructed, and presents a great argument for recognition of neuromuscular changes after concussion. This is something that clinicians may need to begin thinking about and including in their rehabilitation and return to play decisions.

Jane McDevitt said...

You make a great point. The statement the authors make about healthy participants (anything that limited the athlete from participating) could have very well excluded a lot of athletes with CAI or just having a history of a previous ankle injury. I do think we have to be cautious returning concussed athletes to play. When we return athletes with musculoskeletal injuries we rehab them using proprioception exercises; however, we do little to no rehab exercises with concussed patients, let along proprioception techniques to ensure proper neuromuscular re-conditioning. I think there has certainly been a trend of this type of research highlighting that concussed athletes are at a greater risk of lower extremity injury. So, maybe inserting some rehab exercises and not just cardiovascular and strength training to recondition the athlete may better prepare them for full participation.

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