The Influence of Arch Type on Injury in Minimally-Shod Runners


Galbreath K.M., Harrison K.D., McCrory J.L., FACSM, West Virginia University, Morgantown, WV

Greater than 30% of runners are injured annually. In shod runners, individuals with high arches (pes cavus) are more likely to sustain a bony injury and those with low arches (pes planus) are more likely to sustain a soft tissue injury. However, this relationship has not been established in minimally-shod runners. Purpose: To determine if arch type (pes cavus, pes planus) is related to location and type (bony, soft tissue) in minimally shod runners. Methods: Sixteen experienced minimalist runners participated (age: 27.4±10.1 yrs, hgt: 170.3±25.0 cm, mass: 78.1±18.0 kg, gender: 8M, 8F). Informed consent was obtained. Arch index (AI) was obtained via an inked footprint. Subjects were surveyed about the type and location of pain felt while running. Pain in areas of common running injuries (hip, knee, ankle, lower leg, and foot) was quantified using a validated visual analog scale (VAS). Based on survey data, injuries were classified as soft-tissue or bony. Subjects were considered to be injured if pain on the VAS >3. Left and right side data were pooled together. Feet were classified as being pes cavus (AI < 0.21, n=7 feet), or pes planus (AI>0.26, n = 11 feet). Feet with normal arches (n = 14) were excluded from further analysis. Chi-squared analyses were performed to determine if arch type was related the incidence of soft-tissue or bony pain. Separate chi-squared analyses assessed if arch type was a factor in the location of pain. (α = 0.05). Results. Runners with a pes cavus foot were more likely to report soft-tissue pain than those with a pes planus foot (PC: 85.7%, PP: 40.0%; p=0.040). No differences were found in the likelihood of runners with different arch types to report pain in the hip, knee, ankle, foot, or calf (p > 0.05). Conclusions: The results of this pilot study seem to contradict the results of a study on shod runners. We found minimalist runners with a pes cavus foot more likely to report soft-tissue pain whereas others reported shod runners with a pes cavus foot more likely to sustain a bony injury. Soft tissue pain was reported by our subjects in the Achilles tendon, calf muscle, patellar tendon, peroneal tendon, plantar fascia, and a Morton’s neuroma. The loading mechanics of minimally-shod running need to be further investigated to determine why these runners with pes cavus feet are more likely to experience a soft-tissue injury.

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