Effect of foot orthoses and short-foot exercise on the cross-sectional area of the abductor hallucis muscle in subjects with pes planus: a randomized controlled trial. Jung DY1, Koh EK, Kwon OY. J Back Musculoskelet Rehabil. 2011;24(4):225-31.
To prevent overuse injuries related to excessively pronated feet, the strengthening of the foot intrinsic muscles has been recommended. The purpose of this study was to examine the effects of foot orthoses and a short-foot exercise intervention on the cross-sectional area (CSA) of the abductor hallucis (AbdH) muscle and strength of the flexor hallucis (FH) in subjects with pes planus.
Twenty-eight subjects with pes planus were randomly assigned to the foot orthosis (FO) group or the combined foot orthosis and short-foot exercise (FOSF) group for an 8-week intervention. The CSA of the AbdH muscle and the strength of FH were assessed before and after intervention. Data were analyzed using a mixed-model ANOVA.
Significant group by intervention interaction effects were observed in CSA of the AbdH (p=0.009) and strength of the FH (p=0.015). The results of the post hoc paired t-test showed that that the CSA of the AbdH muscle and the strength of the FH significantly increased after the intervention in both groups (p=0.000). The mean CSA of the AbdH muscle and the strength of FH were significantly greater in subjects in the FOSF group compared with subjects in the FO group (mean difference of FO vs. FOSF=13.61 mm(2) in CSA of AbdH muscle; 0.90 kgf in strength of FH; p=0.008).
Results from this study demonstrate that foot orthoses combined with short-foot exercise is more effective in increasing the CSA of the AbdH muscle and the strength of FH compared with foot orthoses alone. Therefore, foot orthoses combined with short-foot exercise are recommended for improving strength of AbdH muscle in subjects with pes planus.
There have been a number of recent studies on the “short foot exercise”. Standing on one leg, you try to shorten your foot by pulling the ball of your foot towards your heel while keeping your toes relaxed. This attempts to isolate the foot intrinsic muscles rather than extrinsic toe flexors which work more with towel bunch type exercises. In this case for 3 sets of 5 repetitions holding each rep for 5 seconds and working up to holding each rep for 10 seconds, 2 times per day for 8 weeks. I should make a video and insert it here.
In this case the exercise was effective at increasing muscle hypertrophy of the foot intrinsics, which are known to be weak and atrophied in conditions such as plantar fasciitis and posterior tibial tendinopathy. This likely contributes to a number of other lower extremity problems including medial tibial stress syndrome, patellofemoral pain, etc. Having tried the exercise myself it did feel like my foot muscles were working, but I also noticed I was was using my tibialis anterior and and posterior tibialis to raise the arch of my foot, so I don’t think it’s entirely isolating the foot intrinsic muscles. Also the intensity of intrinsic muscle contraction feels well inferior to what I get with electric muscle stimulation (EMS) of those muscles. Plus, with EMS isolation of the foot intrinsic muscles is easy. Still it feels effective and might be a good alternative or addition to EMS.
This study was done on those with pes planus (flat feet) that did not have pain so it is still not established that it will help with plantar fasciitis and related conditions. However, I expect it would help as PART of a more comprehensive exercise program including strengthening of the calf musculature (which has recently been shown to help with plantar fasciitis) in addition to strengthening of other LE and hip muscles also shown to be weaker with foot and LE pain. Also there has yet to be a study that has shown exercise might decrease pes planus, which would be interesting to see in future research. I think what isolation studies like this do is demonstrate how each component might fit into a comprehensive physical therapy program, and it would be a mistake to use just this exercise in isolation.
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Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.