Transcript Selection Running Shoes

Running Injuries
and Shoes
Injury Prevention and
Performance Enhancement
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
• jump landings:
– brief duration
– up to 10+ times BW
– forefoot landing
Vertical ground reaction forces
3xBW
2xBW
running
active peaks
walking
1xBW
0
Biomechanics Laboratory, School of Human Kinetcs
Time (s)
Running Forces
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Visual3D animation of walking,
jogging and running.
4 force platforms
10 Motion Analysis infrared
cameras
ground reaction force
centre of gravity
force platforms
centre of pressure
line of gravity
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, hard surfaces, old/poor footwear, poor prep.
• knee/hip/back pain
– anatomical (leg length, abnormal Q-angle, supinated foot)
• shin splints
– mechanically caused by rapid changes in training surfaces
and overuse
• heel contusion (bruise) – poor heel protection, heavy landings
Biomechanics Laboratory, School of Human Kinetcs
Anatomical Indicators of Running Knee Pain
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femoral neck anteversion
excessive Q-angle
knee (genu) varum (bowlegged)
squinting patellae
functional equinus
pronated feet (valgus) in weight-bearing
Ref.
• S L James, BT Bates, LR Osternig, Injuries to runners, Amer J
Sport Med, 6(2):40-50,1978.
Biomechanics Laboratory, School of Human Kinetcs
Q-angle or Quadriceps-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
Pronation versus Supination
• of hand:
– one-dimensional rotation
– turning palm upwards is supination, downwards is pronation
• of foot
– three-dimensional motion
• supination = inversion, plantiflexion and internal rotation
• pronation = eversion, dorsiflexion and external 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
Knee (Genu) Varus or Varum
• inward angulation of the
distal segment
– “bowlegged”
– common in horse riders
and infants
Biomechanics Laboratory, School of Human Kinetcs
Knee (Genu) 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
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; Undermanned 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
Foot Orthotic Appliances
• orthotic with medial forefoot post
for forefoot supination (varum)
• orthotic with lateral forefoot post
for forefoot pronation (valgus or
plantiflexed first ray)
• orthotic with medial heel post for
subtalar varum
Biomechanics Laboratory, School of Human Kinetcs
Heel Protection
• heel cup
– rigid material that doesn’t “absorb”
impact but does spread impact over
larger area
• heel cups with gel cells
– attenuates peak forces by “spreading”
impact over time
• “doughnut” (cushion with hole under
calcaneus)
– same as gel cells but also transfers
impact forces to wider area
Biomechanics Laboratory, School of Human Kinetcs
Impact Protection
• object is to reduce peak forces especially at weak areas
• reduction can be done by spreading impact forces over a wider
area
• distributing the forces to the strongest structures or away from
damaged structures
• delaying the forces by gradually “absorbing” the impact (you
cannot actually decrease the total impact (impulse)
• run on softer surfaces
• decease amount of exposure
• reduce duty cycle (avoid high-impact aerobic dance, i.e., use
step aerobics)
• use appropriate footwear
Biomechanics Laboratory, School of Human Kinetcs
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
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
varum/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
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
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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
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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
Orthoses and Orthotics
• orthosis (singular of orthoses)
– 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
Prostheses
• prosthesis (singular of prostheses)
– 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
Sprinting Prostheses
•
LAUSANNE, Switzerland -Double-amputee sprinter Oscar
Pistorius won his appeal and can
compete for a place in the Beijing
Olympics.
•
IAAF Rule 144.2: 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.
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
Sprinting Prostheses
Disadvantages
Advantages
• very stiff in torsional rotation
therefore difficult in bends
• passive spring therefore
cannot add energy
• slower to accelerate
• lighter therefore lower
locomotor energy cost
• may increase stride length
on straight-aways
Biomechanics Laboratory, School of Human Kinetcs
References
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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 21:623630,2006.
• 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