This was an interesting study in that researchers took 30 young physically active adults with pronated feet and divided them into two groups: one group with a history of prior injury, and another group that had not been injured. The authors analyzed three-dimensional motion during the gait cycle, and used ultrasonography to measure cross-sectional area of the peroneal muscles, flexor digitorum longus and brevis, and the abductor hallucis muscles. The authors concluded the symptomatic pronators demonstrated significantly smaller cross-sectional areas of the flexor digitorum longus and abductor hallucis, and thinner peroneal muscles compared to the asymptomatic group. The symptomatic pronators also had excessive abduction of the forefoot during stance phase, possibly from weakness of the abductor hallucis.
This was an interesting paper because there has been a long-standing argument as to whether or not excessive pronation is a contributing factor to injury. This research shows that it might be possible to prevent people with low-arches from getting injured by strengthening their foot and ankle muscles. This is significant because until recently, excessive pronators were primarily treated with orthotics, which new research shows that orthotics can actually weaken the intrinsic muscles of the arch, producing anywhere from 11 to 17% muscle atrophy in as little as 12 weeks. The take away from this paper is that you can’t go wrong by prescribing strengthening exercises for people with low arches. This is consistent with research showing that foot strengthening exercises can improve horizontal jump distance, vertical jump height, and agility.