1/10/2013 Shoe-Turf Interaction, Injury Risk, and Performance of Elite Athletes Richard Kent, PhD University of Virginia Center for Applied Biomechanics Foot-and-Ankle Subcommittee, NFL UVA Center for Applied Biomechanics • Mechanical and Aerospace Engineering • Founded 1989 with support from U.S. D.O.T. • Engineers, Epidemiologists, and M.D.’s • Staff of ~60 – Faculty from Schools of Medicine, Engineering – 15 Research staff – 40 Support staff and students 1
1/10/2013 UVA Center for Applied Biomechanics • Mechanical and Aerospace Engineering • Founded 1989 with support from U.S. D.O.T. • Engineers, Epidemiologists, and M.D.’s • Staff of ~60 – Faculty from Schools of Medicine, Engineering – 15 Research staff – 40 Support staff and students CENTER for APPLIED BIOMECHANICS 2
1/10/2013 CENTER for APPLIED BIOMECHANICS Applied Fundamental Research Research Measure mechanics •Gait laboratory study of NFL players Characterize during performance Shoe-Turf Interaction Determine loads Mechanics and toe angle that (BEAST) cause turf toe •Literature review •Video analysis Literature Determine loads •Cadaver experiments Existing practices and foot •Relate to NFL players New research deformations that cause Lisfranc Develop injuries Recommended Determine Practices (RPs) •Literature review mechanisms of for NFL •Determine next steps syndesmotic ankle Surfaces sprains CENTER for APPLIED BIOMECHANICS Fundamental Research – How do injuries happen? 3
1/10/2013 CENTER for APPLIED BIOMECHANICS Applied Research and Testing Implementation – Equipment Recommendations, Practices 4
1/10/2013 CENTER for APPLIED BIOMECHANICS Turf toe (Sprain of 1 st metatarsophalangeal joint) Cadaver tests 5
1/10/2013 θ skin 1.0 0.9 “weakest” injured 0.8 at 101 deg. 0.7 Probability of Injury 0.6 50% risk at 108 deg. 0.5 0.4 “strongest” uninjured 0.3 at 132 deg. 0.2 Survival analysis (Weibull distribution) (n=15 cadaver tests) 0.1 0.0 0 20 40 60 80 100 120 140 160 Peak Angle (deg) � 9 Players � Run, cut (outside foot), cut (inside foot), jump, land, start, walk � Maximum big toe joint angle measured 6
1/10/2013 θ skin 1.0 0.9 0.8 Probability of not 0.7 attaining that angle Probability 0.6 while running 0.5 0.4 Cumulative normal distribution (n=8 players) 0.3 0.2 0.1 0.0 0 20 40 60 80 100 120 140 160 Peak Angle (deg) θ skin 1.0 0.9 Probability of not attaining that angle 0.8 while running 0.7 Probability 0.6 0.5 0.4 Cumulative normal distribution (n=9 players) 0.3 Probability of injury in a cadaver 0.2 Survival analysis (Weibull distribution) (n=15 cadaver tests) 0.1 0.0 0 20 40 60 80 100 120 140 160 Peak Angle (deg) 7
1/10/2013 θ skin 1.0 0.9 Probability of not Design Design attaining that angle 0.8 while running Space Space 0.7 Probability 0.6 0.5 0.4 Cumulative normal distribution (n=9 players) 0.3 Probability of injury in a cadaver 0.2 Survival analysis (Weibull distribution) (n=15 cadaver tests) 0.1 0.0 0 20 40 60 80 100 120 140 160 Peak Angle (deg) Lisfranc (First tarsometatarsal joint) 8
1/10/2013 Lisfranc (First tarsometatarsal joint) Film Analysis Summary At Initiation During General 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 9
1/10/2013 Probability of Lisfranc Injury P(I) 1 0.8 0.6 0.4 0.2 60 0 0 40 0.1 0.2 0.3 20 Twist Angle 0.4 0.5 Axial force 0.6 0.7 0 0.8 0.9 1 Cuneiform Coordinates Cuneiform Cuneiform 10
1/10/2013 Second Metatarsal Coordinates \ Medial Cuneiform 2 nd Metatarsal 11
1/10/2013 Motion of 1 st and 2 nd Metatarsals 0.03 0.02 M1_C1_X_load&rot M1_C1_Y_load&rot 0.01 Distance (m) M1_C1_Z_load&rot 0 ⁰ 0 ⁰ 0 40 ⁰ M2_C1_X_load&rot 0 1 2 3 M2_C1_Y_load&rot -0.01 M2_C1_Z_load&rot -0.02 -0.03 CENTER for APPLIED BIOMECHANICS Syndesmotic (“High”) Ankle Sprains 12
1/10/2013 CENTER for APPLIED BIOMECHANICS Syndesmotic (“High”) Ankle Sprains CENTER for APPLIED BIOMECHANICS Applied Research – Shoe-Turf Interaction Torg et al., 1974 Heidt et al., 1996 Livesay et al., 2006 Shorten and Himmelsbach---Biomechanica 2002 13
1/10/2013 CENTER for APPLIED BIOMECHANICS • Test Type 1 – Start from Stop (Translation) Inputs: Vertical force and pressure in actuator Outputs: Does shoe break free? If so, how far and fast does it move? 2.8-kN (630 lb) static preload applied to bearing track Imposed F(t) 170 psi cylinder pressure CENTER for APPLIED BIOMECHANICS • Test 2 – Stop/Cut (Drop) Inputs: Mass, drop height, speed over ground Outputs: Does shoe snag? Vertical force, lateral force, and inversion bending moment. (37.5 kg, 82.5 lb.) 1.5 m/s then release and drop (2 5/8”, 6.7 cm) 14
1/10/2013 CENTER for APPLIED BIOMECHANICS • Test 3 – Twist (Rotation) Inputs: Vertical force and pressure in actuator Outputs: Does shoe break free? If so, how far and fast does it rotate? 2.8-kN (630 lb) static preload applied to bearing track 95 psi cylinder pressure CENTER for APPLIED BIOMECHANICS B ioCore E lite A thlete S hoe-turf T ester (B.E.A.S.T.) 15
1/10/2013 CENTER for APPLIED BIOMECHANICS Detachable cleat Nike Air Zoom Vapor Jet Molded cleat Nike Air Zoom Merciless Destroyer Turf shoe CENTER for APPLIED BIOMECHANICS B ioCore E lite A thlete S hoe-turf T ester (B.E.A.S.T.) 16
1/10/2013 CENTER for APPLIED BIOMECHANICS • SELECTED RESULTS: Start from Stop Test Comparison Across 5 Turfs Displacement 250 Cleat moves 200 Horizontal Displacement (mm) 150 Cleat catches, Cleat then releases 100 “snags” 50 BEAST33: Baltimore Ravens, Shoe VJTD2 BEAST45: NY Giants Grass, Shoe VJTD3 0 BEAST62: NY Giants Turf, Shoe VJTD3 BEAST74: Atlanta Falcons, Shoe VJTD3 BEAST90: Carolina Panthers, Shoe VJTD3 -50 0.0 0.2 0.4 0.6 0.8 1.0 Time (s) CENTER for APPLIED BIOMECHANICS • SELECTED RESULTS : Start from Stop Comparison Across 5 Turfs Displacement Old Bermuda Grass Old Bermuda Grass 250 New Bluegrass 200 Horizontal Displacement (mm) 150 Infill manuf 1 100 Infill manuf 2 50 Infill manuf 2 BEAST33: Baltimore Ravens, Shoe VJTD2 BEAST45: NY Giants Grass, Shoe VJTD3 0 BEAST62: NY Giants Turf, Shoe VJTD3 BEAST74: Atlanta Falcons, Shoe VJTD3 BEAST90: Carolina Panthers, Shoe VJTD3 -50 0.0 0.2 0.4 0.6 0.8 1.0 Time (s) 17
1/10/2013 CENTER for APPLIED BIOMECHANICS Interaction Between Shoe and Turf Nike Air Zoom Merciless Destroyer Nike Air Zoom Vapor Jet CENTER for APPLIED BIOMECHANICS • RESULTS: Start from Stop (Translation) Displacement 250 200 Horizontal Displacement (mm) 150 100 50 Molded on Grass Molded on Fieldturf Artificial Turf 0 Turf shoe on Fieldturf Artificial Turf Turf shoe on Momentum turf Artificial Turf -50 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Time (s) 18
1/10/2013 � Recommendations for Field Performance � Evaluation Rubric for Cleats and Shoes � Based on Research � NFL “university” � 10+ Scientific Papers on Foot-Ankle in 5 Years � Regular Dissemination to Equipment and Field Managers •Goal: Policies and procedures based on technically rigorous research (i.e., knowledge) rather than marketing, historical precedent, or rules of thumb 19
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