Sports Medicine Research: In the Lab & In the Field: Are Side to Side Strength Comparisons Useful in Injury Evaluation and Rehabilitation? (Sports Med Res)
Friday, September 9, 2011

Are Side to Side Strength Comparisons Useful in Injury Evaluation and Rehabilitation?

Elbow flexor and extensor muscle weakness in lateral epicondylalgia

Coombes BK, Bisset L, Vicenzino B.Br J Sports Med. 2011 Jun 27. [Epub ahead of print]

http://www.ncbi.nlm.nih.gov/pubmed/21708935

As sports medicine professionals, one of the first items ingrained into us during our education is to compare an injured joint or muscle to its uninjured counterpart. Through this process we can hopefully identify what is normal for the individual and if strength and stability deficits are present post-injury. Is it possible though, that comparing bilaterally might not be as strong an indicator to normal function as we have been lead to believe, especially if the dominant extremity is injured? In this study, Coombes et al. investigated elbow flexor and extensor strength in individuals with unilateral lateral epicondylalgia (LE).
One hundred sixty-five individuals with the following symptoms were recruited: unilateral pain over the lateral epicondyle for > 6 weeks, aggravation from palpation, gripping and resisted wrist and/or finger extension. All patients in both the affected and control groups (n=54) underwent bilateral dynamometric voluntary isometric testing for both elbow flexion and extension with the maximum value from 3 repetitions in each direction being utilized for analysis. Pain-free grip strength was also measured via a digital grip dynamometer with the patient lying supine and the elbow in a relaxed, extended, and pronated position. The subjects performed 3 grip repetitions per side and were instructed to grip smoothly until pain was elicited on the affected side. Upon comparison, elbow flexion and extension strength of the affected arm was significantly less when compared to the matched arm of controls. The strength of the unaffected arm was comparable to that of the arm-matched controls. Pain-free grip strength was significantly lower for the LE group when compared to controls as well.

While these findings aren't surprising, it should be noted that the dominant extremity was affected in 73% of the subjects. When doing side to side comparison under these conditions, the authors state that the deficits in both elbow flexion and extension strength tend to be underestimated. By virtue of this, getting a true read on the extent of the injury might be difficult due to the pre-existing asymmetry of strength. What are your thoughts on this? Can the same be said for any injury to the dominant extremity? When evaluating your athletes do you take into consideration the fact that the healthy non-dominant side is being used as your frame of reference and more than likely weaker than the healthy dominant extremity? Is it possible that rehabbing an athlete back to a point where the dominant side strength is equal to the non-dominant side is setting them up for future injury?

Written by: Mark Rice
Reviewed by: Stephen Thomas

4 comments:

Natalie Kramer said...

I think this post brings up a lot of good questions. I too diligently check bilaterally for strength and special tests, but often wonder what information I am really gaining from doing it. While the article shows strength deficits are underestimated in the elbow in relation to dominant and non-dominant sides, I wonder in general about the way in which we test strength. In the upper extremity, I have more confidence in my manual strength testing because I know I can give myself the mechanical advantage over the patient. I think even larger deficits would be found in the lower extremity. In the lower extremity, I often find it difficult to know if I am applying enough resistance, especially if the patient is quite a bit larger than me. Even if using dynamometry, questions arise about methods used and amount of force application. When it comes to rehab, I think the strength component is better assessed in terms of functionality. This is an optimal place to use functional outcome measures. A patient usually has a good idea of their strength deficits based on their differences in functionality before injury and while completing rehab. This article is one of many which are making clinicians rethink their evaluation and rehab methods with hopes of creating better practices.

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

Hi Natalie: Great comments! I agree that testing lower extremity strength, even with a dynamometer can be challenging. We recently completed reliability testing for assessing hip strength. While it was challenging it is possible. We found that we needed to identify a position that every patient could assume as well as a position that helped stabilize the clinician. In the end we found that she needed to move the treatment table closer to the wall so that she could use the wall as an external support. It definitely takes some trial and error but it is often possible.

I agree that functional assessments should be a critical part of our evaluations but I don't think we can underestimate the roll of traditional strength assessments. This study further highlights that it is probably less than ideal to use a contralateral control. This makes sense considering there is usually a limb dominance issue as well as evidence that the contralateral limb can have neuromuscular changes after injuries like ACL tears. Based on the growing body of the evidence why should we rely on the opposite limb. Strength assessments, however, are important though because they can demonstrate to the patient (and insurance companies for reimbursement) that they are making progress over time. Even if they aren't running yet they can see that they continue to gain strength. Secondly, strength assessments can help isolate potential problems. For example, I once had an athlete who was one of the fastest runners on her team complaining of IT band pain. Obviously she was functioning at a high level but when you asked her to perform hip extension against gravity with her knee flexed she couldn't lift her thigh off the table. She apparently had been compensating for a considerable strength deficit while still outperforming many of her peers. Strength assessments in this case were important for isolating a problem and then monitoring progress over time.

As you suggested, it is time for us to rethink how we evaluate our strength assessments but they will remain an important part of our evals I think.

Mark A. Rice said...

Natalie, thanks for reading. One of the things that I enjoy most about posting here at SMR is how often I end up questioning everything that I've learned. The contributors at this site do an awesome job of reviewing and recapping articles and challenging all their readers to look critically at a lot of items that seem so fundamental (ie. side to side strength comparisons). Please keep reading and suggesting this site to your friends and colleagues.

Ryan Tonucci said...

Comparing everything bilaterally is only good for the individuals subjective baseline strength. Anything above a MMT which is 3+ becomes subjective to that individuals however anything below that we can objectively measure.

This being said non dominate side and dominate side of each body part is going to have subjective submaximal strengths. For example, if there is a wrestling who leads with his left hand, that hand is going to have more strength than the bilateral hand. That hand may become injured and have a strength weakness however the grip strength dynameters may read identical of the bilaterally hand. This is a strength deficit but as we compare bilaterally we do not see this deficit; even when the athlete may tell use they feel weak.

It is important to understand the sport in which that athlete is in and if the injured body part is their lead leg, plant leg, lead hand, throwing arm, etc. This is so that our bilateral measurement of strength will have more meaning to it. Or the best case scenario would be to have baseline measurements before the injury happened.

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