MMT: A Neuromuscular Perspective

A couple weeks ago I was evaluating someone with low back and groin pain. I did my usual systematic examination that included various mobility and strength measurements. I was surprised to find the patient had MMT (Manual Muscle Test) strength of 2+/5 in her gluteus maximus bilaterally. The patient was in her mid-20's, an avid rock climber, and had reported doing clamshells for strengthening regularly. The patient immediately showed a positive response to approximately 20 repetitions of repeated lumbar sideglides. While her pain wasn't 100% improved, I thought it would be interesting to reassess her gluteus maximus strength. Without doing any strengthening exercises, the patient's strength improved to 3+/5 on her MMT.

This finding brings several different thoughts to mind. The most significant finding is likely just how interconnected the neuromuscular system is. We are all taught in exercise physiology classes that the first 6 weeks of strengthening exercises has a neural impact, before hypertrophy can occur. What stands out to me is just how quickly the MMT findings can change. Just as pain and mobility can quickly change in rapid responders, so can strength. What we should be asking ourselves at this point is what does the MMT actually tell us? What role do strengthening exercises play? It's very possible that the strength deficits we find in many of our patients are at least partially secondary to decreased neural input. If you remember some of our previous discussions on double crush syndrome, decreased neural flow proximally (in a potentially non-painful area) can make nerves more susceptible to injury distally. For example, a patient may lack lumbar mobility, decreasing the axoplasmic flow, which can then decrease the axoplasmic flow to certain muscle, thus appearing “weak.” This is a perfect example of why we must always check the spine systematically. The muscle might not actually be “weak!” It may just be suffering from double crush syndrome.

There are several ways we can address this: manipulation/mobilization, IASTM, repeated motions, and exercise. General strengthening exercises may take the longest as it does not directly solve the “double crush” phenomena. By working on the mobility deficits, we can improve the neural input that may alter our strength measurement findings. I am not saying there isn't a role for strengthening exercises. There are definitely examples of true strength deficits that require strengthening exercises. Even in rapid responders, they can play a role. Think of it similar to IASTM. We are stimulating the affected nerves peripherally which can improve the neural input. The strengthening exercises can also work to truly improve strength. The best approach is likely an eclectic approach.

-Chris

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