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Lessley D.J.,University of Virginia | Lessley D.J.,Biomechanics Research and Consulting LLC | Crandall J.,University of Virginia | Frederick E.C.,Exeter Research Inc. | And 3 more authors.
Footwear Science | Year: 2016

In American football, hyper-dorsiflexion of the first metatarsophalangeal (first MTP) joint is the predominant mechanism of first MTP joint sprains (turf toe). The risk of acute first MTP joint sprain has been found to increase as first MTP joint angle increases. The bending resistance of the shoe dictates the proportion of an externally applied load that can be passed into the shoe (i.e. not through the first MTP joint) and thus may influence the magnitude of flexion imparted to the first MTP joint and hence the risk of injury. The current study introduces the Football American Shoe Tester (FAST), a flexion apparatus designed to measure the bending resistance of American football shoes at angles of forefoot dorsiflexion from 15° to 75°. The FAST was used to quantify the forefoot bending behaviour of a range of American football shoes. Thirty different models of US size 12 shoes were tested. Linearized bending stiffness ranged from 0.27 to 0.8 Nm/deg, while peak torque ranged from 11.8 to 25.5 N m. The testing revealed characteristic differences in torque-angle response across shoe models and quantified the extent of shoe stiffening at angles of dorsiflexion beyond those studied in the past. © 2016 Informa UK Limited, trading as Taylor & Francis Group

Breine B.,Ghent University | Malcolm P.,Ghent University | Frederick E.C.,Exeter Research Inc. | De Clercq D.,Ghent University
Medicine and Science in Sports and Exercise | Year: 2014

PURPOSE: This study assessed initial foot contact patterns (IFCP) in a large group of distance runners and the effect of speed on the IFCP. METHODS: We determined the strike index to classify the runners in IFCP groups, at four speeds (3.2, 4.1, 5.1, and 6.2 ms-1), by measuring center of pressure (COP) with a 2-m plantar pressure plate. Such a system allows a direct localization of the COP on the plantar footprint and has a low threshold value (2.7 cm-2), resulting in more accurate COP data at low ground reaction forces than when obtained from force plate. RESULTS: The IFCP distribution evolves from mostly initial rearfoot contact (IRFC) (82%) at 3.2 m·s to more anterior foot contacts with an approximately equal distribution of IRFC (46%) and initial midfoot or forefoot contact (54%) at 6.2 ms-1 Approximately 44% of the IRFC runners showed atypical COP patterns with a fast anterior displacement of the COP along the lateral shoe margin. Apart from the different COP patterns, these atypical IRFC were also characterized by a significantly higher instantaneous vertical loading rate than the typical IRFC patterns. CONCLUSIONS: The IFCP distribution changes were due to intraindividual alterations in IFCP at higher speeds. That is, 45% of the runners made one or even two "transitions" toward a more anterior IFCP (and 3% shows some other type of transition between initial foot contact styles as speed increases). However, 52% of the runners remained with the same IFCP. Copyright © 2014 by the American College of Sports Medicine.

Determan J.J.,Sole Technology Institute | Frederick E.C.,Exeter Research Inc. | Frederick E.C.,University of Massachusetts Amherst | Cox J.S.,Sole Technology Institute | Nevitt M.N.,Sole Technology Institute
Footwear Science | Year: 2010

Purpose. Despite concerns elicited by the injury-rate statistics for skateboarding, the literature has been silent on biomechanical factors that might be causing or exacerbating these injuries. To help fill this void, we sought to describe the kinetic characteristics of landing from a rail slide, one of the more high-risk, albeit common, maneuvers practiced by skateboarders. Methods. Twelve top-amateur or professional skateboarders (BW=688±89 N) performed rail slide maneuvers down a steep handrail before landing on a force plate. We recorded ground reaction force (GRF) data whether the subjects landed successfully (L) on their skateboards, or, bailed-out (BO), i.e. landed on their feet. Results. Vertical GRF (VGRF) during L had an initial peak, due to skateboard contact, immediately followed by a set of impact peaks (mean=7.98±1.32 (SD) BW) representing landing on the board. BO showed a VGRF impact peak rising to a significantly higher (P<0.05) mean of 12.09±2.63 BW. Conclusions. These data suggest that the skateboard provides significant shock attenuation. However, because BO landings are frequent, the relatively high peak ground reaction forces are a cause for concern. Given the musculoskeletal immaturity of typical skateboarders, clinicians should be aware of these high impact forces, and footwear manufacturers should explore ways to reduce peak pressures, and high impact and shear forces in the heel, forefoot, and toe box. © 2010 Taylor & Francis.

TenBroek T.M.,New Balance Athletic Shoe Inc. | TenBroek T.M.,University of Massachusetts Amherst | Rodrigues P.A.,New Balance Athletic Shoe Inc. | Rodrigues P.A.,University of Massachusetts Amherst | And 2 more authors.
Journal of Applied Biomechanics | Year: 2014

The purpose of this study was to: (1) investigate how kinematic patterns are adjusted while running in footwear with THIN, MEDIUM, and THICK midsole thicknesses and (2) determine if these patterns are adjusted over time during a sustained run in footwear of different thicknesses. Ten male heel-toe runners performed treadmill runs in specially constructed footwear (THIN, MEDIUM, and THICK midsoles) on separate days. Standard lower extremity kinematics and acceleration at the tibia and head were captured. Time epochs were created using data from every 5 minutes of the run. Repeated-measures ANOVA was used (P < .05) to determine differences across footwear and time. At touchdown, kinematics were similar for the THIN and MEDIUM conditions distal to the knee, whereas only the THIN condition was isolated above the knee. No runners displayed midfoot or forefoot strike patterns in any condition. Peak accelerations were slightly increased with THIN and MEDIUM footwear as was eversion, as well as tibial and thigh internal rotation. It appears that participants may have been anticipating, very early in their run, a suitable kinematic pattern based on both the length of the run and the footwear condition. © 2014 Human Kinetics, Inc.

TenBroek T.M.,New Balance Athletic Shoe Inc. | Rodrigues P.,New Balance Athletic Shoe Inc. | Frederick E.C.,Exeter Research Inc. | Hamill J.,University of Massachusetts Amherst
Footwear Science | Year: 2013

Introduction: Research on minimal footwear hasn't utilised runners who habitually wear typical training footwear and therefore what adjustments to running patterns are made and how quickly they occur is unknown. Purpose: The purposes of this study were: 1) to investigate how kinematic patterns are adjusted while running barefoot and in footwear with systematic changes in shock attenuating material; and 2) to determine the time it takes for adjustments to occur when little is known about the footwear condition before running commences. Methods: Ten male heel-toe runners performed treadmill runs of 6 minutes in thin, medium, and thick footwear and barefoot. Participants ran immediately after putting shoes on to limit information about each footwear condition. Standard kinematics and acceleration signals were captured. Repeated measures analysis of variance (ANOVA) was utilised (p < 0.05) to determine differences across footwear conditions and time. Results: The foot was flatter at touchdown (due to a more vertical leg segment and more plantar flexion), the knee had reduced excursion, and stance times, eversion and tibial rotation excursions were greater in the thin footwear or when barefoot. Several variables were adjusted from the initial steps to later in the run. Acceleration standard deviations had more variability during initial steps than immediately following. Discussion: Many kinematic adjustments agreed with previous works though participants did not adopt a midfoot or forefoot strike pattern. Experimental design and participant knowledge and experiences may be contributing to discrepancies in footstrike patterns. Runners sensitive to eversion and tibial internal rotation should use caution when barefoot or in minimal footwear. Finally, the greatest kinematic changes occurred within the first six to eight steps, however more subtle changes continued throughout the six minute run. © 2013 Copyright Taylor and Francis Group, LLC.

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