KIN 100 1st Edition Lecture 17 Gait Biomechanics and Footwear Lecture by Carl Running walking goals rotational linear motion move forward Speed Efficiency how economical is movement Stride cycle Walking right foot strike to next right foot strike or left foot stance phase foot in contact with ground swing phase foot off of ground Single support only one leg on ground double support both legs on ground only in walking Stride cycle running stance phase much shorter one foot only swing phase flight phase no feet in contact with ground only running Stride stance swing as speed increases stance and flight times change stance time decreases Quantifying stride cycle stride rate frequency of strides sec stride length distance covered by one stride distance between one right foot touch and the next stride rate x stride length speed Efficiency Increased via minimize Vertical COM displacement dont want to waste energy moving up and down economical running com stays at a constant height Relationship bewtween force and velocity 2nd law of motion force m x a early in stance runners foot is exerting a forward directed force on ground ground pushes back with equal force ground reaction force breaking stage posterior acceleration force from ground is opposite of direction late stance propulsive force anterior acceleration increase speed force in direction of motion horizontal forces constant speed breaking forces propulsive forces slowing down breaking force propulsive force accelerating breaking force propulsive force horizontal forces and efficiency always include breaking and accelerating try and minimize force producing equal breaking and propulsive forces minimize breaking force Quantifying motion during gait pronation angle rearfoot angle tibial angle pronation ankle rolls inward supination ankle rolls outward pronation and supination pattern normal supination neutral pronation neutral supination Footwear Shoe Type 1960s running shoes all similar rubber outsole cushioned midsole EVA foam nylon upper material fitness boom of 1970s brought more runners 1980 companies surveyed more when making shoes majority of injury training error excessive foot motion over pronation poor body alignment injury prevention valgus inward bending of knees distal segment knock knees varus bow legged outward bending of distal segment patellofemoral pain pain originating from posterior surface of the patella and the femur bone achilles tendonitis overuse injury straining tendon plantar fasciitis inflammation of the tendon tissue tissue on bottom of foot tibial stress syndrome shin splints injury interventions orthotics put something into shoe to change how foot interacts with the ground gait retraining teach body how to move in more economical way shoe design change stiffness of materials change geometry of the cushioning brooks introduced varus wedge controls foot motion 3 types of shoes also used for foot classification motion control stability cushioned neutral minimalist shoes level platform zero lift shoe foot classification using pronation to assign shoes has limited scope now looking at coupling at knee ankle hip whole foot motion not just pronation foot strike patterns rearfoot runners land with heal transition to midfoot and push off midfoot strikers land flat transition to toe land on toe but heel touches forefoot strikers land on the ball of the foot no heel touch Forefoot ff vs rearfoot rf impact peak occurs early in stance phase active peak occurs in middle not studies have supported that rearfoot is running is bad for you doesn t decrease risk of injury just location of injury drastic change can cause injury elite distance runners change foot strike pattern over course of race increase speed greater tendency to land on balls of feet Barefoot minimalist running advocates believe it allows body to move more naturally not end all cure all environment tarahumara don t run on cement gradual and smooth transition works don t do it all at once might be more useful as a tool in training to strengthen muscles instead of complete change