How Core Muscles Can Affect The Lower Extremity

Author(s): 
Brian Fullem, DPM

What The Research Reveals

Fredericson has published several significant articles proving the association between weakness in the hip abductors and running injuries. One study compared a group of 24 runners with ITBS to a control group of 30 healthy runners.3 The injured group had significantly weaker hip abductors. After six weeks of strengthening of the core muscles primarily through eccentric exercises, 22 of the 24 runners in the injured group were back to full activity. Traditional treatment of ITBS had focused on stretching but with Fredericson’s work, the focus should now shift to strengthening.
In another study of recreational runners, researchers compared 30 runners with injuries to 30 randomly chosen healthy runners.4 The runners had various injuries throughout the whole leg and there was a statistically significant difference in hip abductor strength in the injured runners’ affected limb versus the healthy side. The uninjured runners did not have any difference in hip abductor strength. A third study showed a correlation between patellofemoral pain and hip abductor weakness.5 Thirteen athletes with unilateral patellofemoral pain underwent examination and a significant difference was present in hip abductor strength in comparison to the healthy limb.

Key Diagnostic Tests For Hip Abduction
In order to examine the strength of the hip abductors, one should start with non-weightbearing testing. Test patients on their side with the leg raised up laterally. Make sure they rotate their hips forward on the side that is not on the table. This will eliminate the influence of other muscles such as the quadriceps. Have the patient resist while you push down the leg.
Another test is checking for a Trendelenberg sign on the examination table. Have the patient bridge up off a flat table with the feet flat. The patient should then fully extend one leg out with the knee locked. If the hip drops on the side of the extended leg, that is a sign that the opposite hip abductors are weak. Physicians can also look for a Trendelenberg sign during the gait examination.

A Guide To Core Strengthening Exercises
All of the recent studies point toward the addition of hip abductor and core strengthening as being beneficial for the training of distance runners.
In regard to strengthening of the core muscles, there is an excellent guide at http://www.coachr.org/core_stabilisation_training_for.htm. Fredericson has developed this program specifically for runners to help prevent injuries. The plan includes the use of dynamic exercises, including the use of a stabilization ball, rocker board, medicine ball, lunges and step-ups. Injured runners can begin simply with side leg lifts.
I recommend people lie on their side and slide the leg up a wall with the back of the leg against the wall and the foot pointed down. Start with one set of 20 on each side and progress to three sets of 20 per day.
I also begin people on bridging up exercises, and side and front planks. One can find another excellent core program at smiweb.org.

In Conclusion
Indeed, weakened core muscles can lead to increased pronation and subsequent lower extremity pain. Podiatric physicians should consider this possibility if athletes do not respond to conventional treatments for conditions such as plantar fasciitis and Achilles tendonitis.
There are simple tests one can perform to detect hip abduction. If core muscles are contributing to lower extremity ailments, one may need to consider the possibility of a physical therapy referral.

Dr. Fullem is a Fellow of the American College of Foot and Ankle Surgeons, and the American Academy of Podiatric Sports Medicine. He is board-certified in foot and ankle surgery by the American Board of Podiatric Surgery. Dr. Fullem is in private practice in Newtown, Ct.

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