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Selecting Running Shoes. Injury Prevention and Performance Enhancement. Shoe Anatomy. sole: bottom of shoe insole: interior bottom of a shoe some models have removable insoles outsole: material in direct contact with ground (tread)
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Selecting Running Shoes Injury Prevention and Performance Enhancement
Shoe Anatomy • sole: bottom of shoe • insole: interior bottom of a shoe • some models have removable insoles • outsole: material in direct contact with ground (tread) • midsole: material between insole and outsole (made of EVA or PU) • upper: top of shoe that holds shoe to foot • Low-cut, mid-cut and high-cut uppers • toe box: area that holds toes and heads of metatarsals • vamp: material over the instep • heel counter: specialized area at heel that is relatively rigid in running shoes • last: form for shaping shoe (straight, semicurved, curved) and footprint Biomechanics Laboratory, School of Human Kinetcs
active peaks Forces during Walking vs. Running • walking: • long duration • double “active” peaks • +/-20% body weight • running/sprinting/jumping: • brief durations • single “active” peak • 3 times BW • heel-toe landing • landings: • brief duration • up to 10+ times BW • forefoot landing Biomechanics Laboratory, School of Human Kinetcs
Why Does Running Cause Injuries? • ground reaction forces are high (3x body weight) • impact is brief therefore little time for muscles to dissipate forces • some people’s anatomy may predispose injury (leg length discrepancy, excessively pronated/supinated feet or varus/valgus knees) • running surfaces are rigid (roads, sidewalks, frozen earth) • people tend to over-train (amount per day, no recovery days) • warm-up and stretching are often neglected Biomechanics Laboratory, School of Human Kinetcs
Running Injuries • plantar fasciitis • anatomical, excessive heel impacts, poor running mechanics • heel spur, hammer toes, bunions • poor shoe fit • ankle and foot sprains • mechanically caused by landing off balance or on an obstacle • tibial stress syndrome/fracture • overuse injury, training on hard surfaces, old or poor footwear • knee/back pain • anatomical differences (leg length, abnormal Q-angle) • shin splints • mechanically caused by rapid changes in training surfaces and overuse Biomechanics Laboratory, School of Human Kinetcs
Purposes of Shoes • protection from: • sprains (high cut shoes may help but reduce flexibility) • cuts and abrasions (strong uppers may increase weight and decrease mobility) • punctures from nails, rocks, slivers etc. especially for road running (thick soles help but reduce efficiency) • traction or prevent slippage • tread helps especially on wet surfaces • spikes and studs (check rule books) • cushioning • in midsoles (reduces efficiency) • ventilation • air circulation, water drainage or waterproof? Biomechanics Laboratory, School of Human Kinetcs
Cut of Uppers • low cut • greatest mobility • mid cut • high cut • may help to control ankle sprains Biomechanics Laboratory, School of Human Kinetcs
Running Shoe Types • Cushion: • for high-arch feet, underpronator • extra cushioning in the midsoles to help absorb shocks; their soles have a curved or semicurved shape (last) that promotes a normal running motion • Motion control: • for flat feet or feet that pronate after landing • straight last and a more rigid midsole than other running shoes, these help keep your feet properly aligned. • Stability: • for normal or neutral feet • semicurved last, but the less rigid midsoles allow feet to strike the ground naturally Biomechanics Laboratory, School of Human Kinetcs
Cushioning • measured by durometer (hardness) • mainly in midsole • cushioning is helpful for hard surfaces • especially as muscles start to fatigue • greater cushioning means less efficiency • may cause ankle instability and sprains • gel or air cushions cause landing instability • cushioning columns are better • breaks down over time • impact testing for endurance Biomechanics Laboratory, School of Human Kinetcs
Biomechanical Efficiency? • all shoes absorb and dissipate energy • cushioned running shoes absorb the most energy • the greater the cushioning the more lost energy • sprinters’ shoes have the least cushioning and are therefore the more efficient • bare feet are most efficient but traction may be compromised and they offer little protection from stones, heat or sharp objects Biomechanics Laboratory, School of Human Kinetcs
Athletic Shoe Types • basketball/volleyball • sturdiest with thick midsole cushioning • for wooden floors and high impacts • cross-trainers • most versatile athletic shoes available • less cushioning • spiked for track & field • greatest traction on rubberized tracks • lightest and fastest • studded for soccer or rugby etc. • greatest traction of grass or artificial turf Biomechanics Laboratory, School of Human Kinetcs
Pronation versus Supination • of hand: • one-dimensional rotation • turning palm upwards is supination, downwards is pronation • of foot • three-dimensional motion • inversion, plantiflexion and internal rotation • supination is turning foot so that plantar surface (bottom of foot) is directed medially (towards midline) • pronation is turning foot so that plantar surface (bottom of foot) is directed laterally (away from midline), this is most common motion when a foot lands during running Biomechanics Laboratory, School of Human Kinetcs
Supinated Foot Pronates during Landings • foot is supinated at landing pronates during loading • orthotics help to reduce rates of pronation during landings (Bates et al. 1979; Mündermann et al., 2003; Stackhouse et al., 2004) but it is unclear how they affect the kinetics (MacLean et al., 2006) Biomechanics Laboratory, School of Human Kinetcs
Orthoses and Orthotics • orthosis • device added to support an anatomical structure • i.e., brace or wedge • e.g., custom foot orthotic (CFO) appliances (“orthotics”), ankle-foot orthoses (AFO) and knee braces Biomechanics Laboratory, School of Human Kinetcs
Foot Orthotic Appliances • orthotic with medial forefoot post for forefoot supination (varus) • orthotic with lateral forefoot post for forefoot pronation (valgus or plantiflexed first ray) • orthotic with medial heel post for subtalar varus Biomechanics Laboratory, School of Human Kinetcs
References • Bates B et al. Amer J Sports Med 7:338-342,1979. • Huberti HH & Hayes WC. J Bone Jnt Surg 66A:715-724,1984. • Insall J, Falvo KA & Wise DW. J Bone Jnt Surg 58A:1-8,1976. • MacLean C, McClay Davis, I & Hamill J. Clin Biomech 21:623- 630,2006. • Mündermann A et al.Clin Biomech 18:254-262,2003. • Stackhouse CL, McClay Davis, I & Hamill J. Clin Biomech 19:64-70,2004. Biomechanics Laboratory, School of Human Kinetcs
Knee (Genu) Valgus • valgus: outward angulation of the distal segment • distal segment is rotated Laterally • distal means farther away from the body’s centre • “knock-kneed” • common in women Biomechanics Laboratory, School of Human Kinetcs
Knee (Genu) Varus • inward angulation of the distal segment • “bowlegged” • common in horse riders Biomechanics Laboratory, School of Human Kinetcs
Quadriceps-angle or Q-angle • “quadriceps-angle” is formed in the frontal plane by two line segments: • from tibial tubercle to the middle of the patella • from the middle of the patella to the anterior superior iliac sine (ASIS) • in adults is typically 15 degrees • Increases or decreases in the Q-angles are associated with increased peak patellofemoral contact pressures (Huberti & Hayes, 1984). • Insall, Falvo, & Wise (1976) implicated increased Q-angle in a prospective study of patellofemoral pain. Biomechanics Laboratory, School of Human Kinetcs
Prostheses • prosthesis • device that replaces an anatomical structure • i.e., an artificial limb • e.g., solid-ankle, cushioned-foot (SACH) foot, FlexFoot, C-knee, Mauch leg Biomechanics Laboratory, School of Human Kinetcs
LAUSANNE, Switzerland -- Double-amputee sprinter Oscar Pistorius won his appeal Friday and can compete for a place in the Beijing Olympics. Olympic Rule: For the purpose of this Rule the following shall be considered assistance, and are therefore not allowed: e) use of any technical device that incorporates springs, wheels or any other element that provides the user with an advantage over another athlete not using such a device. Sprinting Prostheses It's a great day for sport. I think this day is going to go down in history for the equality of disabled people. -- Oscar Pistorius Biomechanics Laboratory, School of Human Kinetcs