Sports Medicine Research: In the Lab & In the Field: Guest Post: Single-Limb Tasks Identify Lower Extremity Functional Deficits (Sports Med Res)


Friday, July 8, 2011

Guest Post: Single-Limb Tasks Identify Lower Extremity Functional Deficits

Utilization of Modified NFL Combine Testing to Identify Functional Deficits in Athletes Following ACL Reconstruction

Myer GD, Schmitt LC, Brent JL, Ford KR, Barber Foss KD, Scherer BJ, Heidt RS, Divine JG, Hewett TE. J Orthop Sports Phys Ther. 2011 June; 41(6): 377-388.

Anterior cruciate ligament (ACL) tears affect a large group of young athletes. Functional deficits such as strength deficits and decreased functional scores have been reported up to 2 years after an ACL reconstruction. Unfortunately, there is a lack of objective clinical measures that can identify these deficits and can be used to influence return to play decisions. This highlights the need for a performance-based, on-field assessment tool capable of detecting lower extremity deficits in the later stages of rehabilitation. Therefore, Myer and colleagues, attempted to identify unilateral lower limb deficits using a modified version of the NFL Combine tests (modified double-limb tests) and single-limb tests. Eighteen ACL reconstructed patients that were cleared to return to play and 20 matched, healthy-control athletes performed functional tests that included broad jump, vertical jump, modified agility T-test, timed hop, triple hop, single hop, and crossover hop (full text and slides available online for detailed descriptions). The authors reported that single-limb tasks (e.g., single hop test, triple hop) detected significant functional deficits in individuals who had undergone ACL reconstruction, while the modified bilateral-limb tasks (e.g., modified agility T-test) were not sensitive enough to identify these deficits.

Overall, this study highlights the effectiveness of using single-limb tasks (e.g., single hop for distance, crossover hop for distance, triple hop for distance) to identify functional deficits in ACL reconstruction patients that had been previously cleared to play. Properly identifying these deficits may be critical in determining an athlete’s return to play status, minimizing the risk for reinjury, and identifying functional deficits that should be addressed in rehabilitation or a strength training program. The authors suggest that we need more research exploring other combinations of functional tasks and measures of movement quality (e.g., does the hip adduct during a hop landing). This study supports other research [see Eitzen 2010], which indicated that these single limb tests can detect functional deficits. Clinically, these tests are fairly easy to administer without the use of extraneous materials or equipment. Is this something you currently use in your return to play decisions? If not, what is it about these test that makes you apprehensive?    

Written by: Kyle Harris
Reviewed by:  Jeffrey Driban


Amy castillo said...

This brings up the thought. Is it a motor or proprioceptive deficit. Or is it fear.

Andrew Kubinski, MS said...

Does fear cause a motor or proprioceptive deficit?

Tommy Nowakowski said...

I use alot of SL (single leg) and DL (double leg) "tests" to assess my ACL rehabilitations. I also feel that the SL tests are much better indicators of where this athlete is functionally. You cannot totally dismiss these DL activities however many of these "DL activities" have significant single leg time incorporated in them. The key I believe, however, is not using SL activities just as functional measures but also emphasized throughout the rehabilitation process.

Jeffrey B. Driban, PhD, ATC, CSCS said...

Amy, Andrew, and Tommy: Thanks for the comments. I think that some of the deficiencies we are seeing with these tasks are a related to a combination of neuromuscular deficiencies and apprehension. Apprehension may influence muscle tone and even the response we have to startling stimuli (our startle response). Many of us have also seen and/or read evidence in the literature that additional cognitive distractions can alter balance performance (apprehension may be a subtle cognitive distraction). With that said there has been ample evidence that there is chronic quadriceps weakness after ACL tears (and some evidence that it may be a bilateral phenomenon; which is concerning). I included below some links to abstracts that discuss chronic quadriceps weakness following ACL injuries. I'm not sure if people have really assessed if we also see chronic hip weakness after an ACL injury (that would be interesting).

Tommy, I agree with you that we shouldn't dismiss the double-leg tasks. They are important components of sports activities. As Kyle noted in the post, the authors suggested that other double-leg tasks (besides those tested in this study) should be evaluated. I also agree that single-leg tasks are very valuable in rehabilitation. I like them because it keeps the patient from shifting weight to the healthier leg. It's also a nice way of demonstrating to the patient that they still are limited.

Some interesting articles related to chronic strength deficits following an ACL injury:

For the latest research check out the JAT supplement for NATAREF Free Communication abstracts on this topic by Thomas AC (pg S-102), Klykken LW (pg S-104), Lepley AL (pg S-107)

Link to full-text of supplement:

Kyle Harris said...

Jeff, you hit many important points here. One thing you touched on that I think is very important is the use of the single leg activities to, as I keep thinking, "keep the athlete honest" for lack of a better term and prevent them from using their healthier leg. We deal with a highly motivated group of patients who want to RTP as soon as possible. The SL tasks are a great way to view the patient's true ability and deficits. With this all being said, we cannot dismiss the DL tasks. As Tommy pointed out so correctly, the DL tasks do have significant portions of the test in which the athlete is relying on a single leg. I do think that using DL tasks, where the athlete moves from the healthier leg to the injured leg can be very effective in demonstrating performance deficits as compared to a healthier "control" leg and also in showing the athlete that they are functionally limited as Jeff pointed out.

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