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Department
of Podiatry
Biomechanics
of Running
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Outline
the
running cycle
spatial parameters
runner's varus (?)
impact forces
overuse injuries
do
running shoes cause injury? (Robbins-Gouw hypothesis)
CD-ROM
component of lecture:
"Running & Sprinting: a dynamic analysis"
BUNDOORA LIBRARY AV 612.76
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The
running cycle
- no
double support phase
- three phases
stance (40%)
float (30%)
swing (30%)
- stance consists of
contact, midstance, propulsion
- 'float' phase
body airborne, no foot contact
consists of forward swing and foot descent
- the duration of each phase is relative to the speed of running
jogging: stance > swing
distance: stance = swing
sprinting: stance < swing
Spatial
parameters
- step and stride length much greater than walking
- stride width much narrower
- no double support phase
uphill running
- shorter stride length
- increased stride rate
downhill running
- longer stride length
- decreased stride rate
NB: at any given running speed, each individual has an optimal combination
of stride length and rate to minimize energy requirements
Increased speed leads to
- increased hip flexion
- increased knee flexion
- increased forward trunk lean
- increased float phase duration
- decreased support phase
Runner's
varus
- foot
must be placed under CoG, due to lack of double support
- requires adduction of femur in the acetabulum
- increased varus position at heel strike
- this varus position favours increased STJ pronation, particularly
in females
Impact
force
- F=MV,
therefore running will result in greater impact force than walking
- two peaks:
heel strike (2 X BW)
midstance (3 X BW)
- joint compressive forces in the foot may reach up to 10 X BW
- high potential for stress fracture
- rapid STJ pronation and knee flexion
Overuse
injuries
- massive
increase in number of joggers in last 20 years
- estimated thirty million joggers in the USA (Nigg, 1986)
- Runners World survey found that two out of three joggers are affected
by injuries every year
- the knee is most common site of injury (Nigg, 1986)
Factors associated with overuse injuries
- impact force
- hard surfaces
- stress fractures
- downhill running: shin splints, patellar tendinitis
- lack of flexibility: esp. achilles and hamstrings
- overstriding: hamstrings, knee pain
- anatomy
- shoes: a large lateral flare provides ground reaction forces with
a longer lever arm for pronating the STJ. This will increase the velocity
of contact phase pronation and may predispose to injury
 -
running
on one side of road
- environmental LLD
Do running
shoes cause injury ?
Evidence:
... large increase in overuse injuries over the last 20 years
... a Boston marathon study found that there was a higher incidence
of overuse injury in subjects who wore more expensive shoes
very low incidence of injury in barefoot runners
Robbins-Gouw hypothesis:
running shoes cause injury due to creating a perceptual illusion of
lower impact force
excessive cushioning decreases proprioceptive feedback
body unable to judge severity of impact
reduced innate impact moderating behaviour
increased impact
Click
here to learn more about common running injuries.
Summary
- significantly
altered mechanics
- floatation phase
- impact forces up to 3 X BW
- rapid contact phase pronation
- increased varus heel strike
- not necessarily heel to toe pattern
- increased
incidence of injury
- different orthotic requirements (see links from this page - not
examinable)
 References
Nigg
BM (1986) Biomechanics of running. Human Kinetics Publishers, Illinois,
Chapter 1.
Subotnick SI (1975) Podiatric Sports Medicine. Futura Publishing company,
Chapter 3.
Links:
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