The Effect of Foot Type on In-shoe Plantar Pressure During Walking and Running

Abstract

PURPOSE: The purpose of this study was to determine if foot type (flat or normal) resulted in loading differences during walking and running. This information may aid in understanding which individuals are at increased risk for certain foot injuries. METHODS: 54 healthy subjects (108 feet) with an average age of 24.52 ± 3.9 years walked and ran over a 10 m walkway at 1.8 m/s and 3.3 m/s, respectively. Each subject completed 5 trials in each condition while speed was controlled by 2 pairs of infrared photocells. In-shoe pressure data was collected using a Pedar-X system collecting at 100Hz. Contact area, maximum force, and the force time integral were analyzed in the rearfoot, the medial and lateral midfoot, the medial, middle, and lateral forefoot, the hallux, and the lesser toes. Foot type was determined by examining navicular height, arch angle, rearfoot angle, and a clinical score given by a foot and ankle orthopaedic surgeon. To be classified as a flat foot, 3 of these 4 variables had to classify the foot as flat. Paired samples t-tests were used to determine statistical differences (α=0.05). RESUITS: 31 feet were denned as flat (29%) while 77 were normal (71%). During walking, flat feet demonstrated a decrease in rearfoot contact area and maximum force in the middle forefoot. In addition, flat feet demonstrated an increase in contact area, maximum force and the force time integral in the medial midfoot. However, flat feet demonstrate a decrease in rearfoot contact area when compared with normal feet in walking. During running, flat feet demonstrated an increase in contact area, maximum force, and the force time integral in the medial midfoot. In addition, flat feet demonstrated an increase in maximum force and the force time integral in the lateral midfoot and rearfoot. Finally, flat feet demonstrated an increase in both total foot contact area and contact time during running. All results were statistically significant (p<0.04). CONCLUSIONS: During running, the total foot contact area and contact time, as well as the maximum force and force time integral in the lateral midfoot were significantly different based on foot type, which did not occur during walking. These loading differences between foot types could be important in understanding and assessing the risk factors for metatarsal stress fractures.