Pronated feet are stronger, okay?
How often have we been told that a pronated foot must be a weak foot? That because the muscles cannot possibly be being loaded properly they must be suffering?
And, how often have you read that a pronating foot needs to be "strengthened", often with the suggestion the arch height will improve and that this should be done via "foot core" exercises. You can read my thoughts on this in my blog.
Well, a brand new study really puts the heat on this position, and all those people who have been making these statements for so long, have suddenly gone very quiet!
Comparison of foot muscle morphology and foot kinematics between recreational runners with normal feet and with asymptomatic over-pronated feet.
Zhang et al,
Gait & Posture, Volume 54, May 2017, Pages 290–294
Over-pronated feet are common in adults and are associated with lower limb injuries. Studying the foot muscle morphology and foot kinematic patterns is important for understanding the mechanism of over-pronation related injuries. The aim of this study is to compare the foot muscle morphology and foot inter-segmental kinematics between recreational runners with normal feet and those with asymptomatic over-pronated feet. A total of 26 recreational runners (17 had normal feet and 9 had over-pronated feet) participated in this study and their foot type was assessed using the 6-item Foot Posture Index. Selected foot muscles were scanned using an ultrasound device and the scanned images were processed to measure the thickness and cross-sectional area of the muscles. Muscles of interest include abductor hallucis, abductor digiti minimi, flexor digitorum brevis and longus, tibialis anterior and peroneus muscles. Foot kinematic data during walking was collected using a 3D motion capture system incorporating the Oxford Foot Model. The results show that individuals with over-pronated feet have larger size of abductor hallucis, flexor digitorum brevis and longus and smaller abductor digiti minimi than controls. Higher rearfoot peak eversion and forefoot peak supination during walking were observed in individuals with over-pronated feet. However, during gait the forefoot peak abduction was comparable. These findings indicate that in active asymptomatic individuals with over-pronated feet, the foot muscle morphology is adapted to increase control of the foot motion. The morphological characteristics of the foot muscles in asymptomatic individuals with over-pronated feet may affect their foot kinematics and benefit prevention from injuries.
This article is the fuse I plan to light in relation to a bigger discussion of pronation. And.. I plan to make the case that, with the exception of the really big outlier cases of "overpronation", pronation is good!
The take-home message from this study lies in the word "asymptomatic". So many of us for so long have been banging home the message that, in relation to a "pronating foot" the rules change between symptomatic and asymptomatic cohorts. This study provides more evidence that there is no rational reason to strengthen a pronated foot.
Watch this space for more updates.
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Director of Bartold Clinical