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Biomechanics of Running
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Characteristics of Running Cycle
Biomechanical Analysis of Running
Special Considerations in Sprinting
Special Considerations in Jogging
- Hamilton, N., & Luttgens, K. 2002. Kinesiology, Scientific Basis of Human Motion, 10thed.
Boston, MA: McGraw-Hill. Chapter 19, pp. 480-484.
- Adelaar, R.S. 1986. The practical biomechanics of running. American
Journal of Sports Medicine 14:497-500.
- Cavanagh P.R. 1987. The biomechanics of the lower extremity action in distance running.
Foot and Ankle 7:197-217.
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Characteristics of Running Cycle
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Running cycle
contact phase (support phase; drive phase)¡G one foot is in contact with the ground, i.e., from foot strike to toe-off
foot strike
midsupport
take off
swing phase¡G the lower extremity is swinging through the air, i.e., from toe-off to foot strike
follow through
forward swing
foot descent
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Characteristics of running
stride length and frequency tend to increase with increased running speed
stride length depends on leg length, range of motion of hip, and strength of leg extensors
stride frequency depends on speed of muscle contraction and the skill of running
for speeds over 7 m/s, a increment in stride length is small but the stride frequency is significantly greater
Both feet tend to fall on the same line along the path of progression.
With increasing running speed, duration of contact period decreases but that of swing phase increases.
As the foot strikes on the ground, the foot is in front of the COM of the body but the distance from foot contact to the COG is shorter
in running as compared to walking. This distance becomes shorter with the increase of the speed.
In barefoot running, the degree and duration of maximum foot pronation are increased
as compared to that in running with shoes and/or foot orthoses.
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Comparisons of running with walking
to distinguish walking from running
a double swing phase during running while a double support phase during walking
the body is totally airborne for a period of time during running whereas at least one part of the body (usually indicating foot)
contact the ground for the whole gait cycle during walking
comparisons of kinematic and kinetic parameters of running with those of
walking
| |
running |
walking |
| entire cycle |
swing phase longer |
stance phase longer |
| duration of stance phase |
shorter |
longer |
| double support period |
absent |
present |
| duration of swing phase |
longer |
shorter |
| floating period |
present |
absent |
| stride length |
longer |
shorter |
| stride frequency |
higher |
lower |
| position of body COM |
lower |
higher |
| vertical oscillation of body COM |
less |
more |
| linear and angular velocity of lower extremity |
faster |
slower |
| required ROM |
greater |
less |
| muscle activities |
greater |
less |
| leg drive during swing phase |
muscular |
momentum (pendulum) |
| foot progression line |
1 line along midline of body |
2 parallel lines |
| ground reaction force |
2.5~3 times body weight |
~90% of body weight |
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Biomechanical Analysis of Running
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Foot strike
patterns of foot strike
heel strike¡G better for long-distance running because the heel pad has a better ability to absorb high impact force
midfoot strike or whole-foot strike
forefoot strike
only can be used in sprinting
metatarsalgia or stress fracture of the central metatarsal bones commonly occurs in the jogger with forefoot strike
because of repetitive large loads onto the central metatarsal heads
At the moment of foot strike, the foot is slight supinated with the tibia in some external rotation.
The most important event during foot strike is to absorb the initial impact of the foot striking the ground through
rapid extension of the hip
flexion of the knee
internal rotation of the tibia
pronation of the subtalar joint
shoes and/or orthoses
initial impact (impulse)
impulse = F ´ t
initial ground reaction force = 2.5~3 times body weight, depending on the running speed
heel pad has better ability to absorb initial impact than other adipose tissues in human body
improvement in materials of shoes (e.g. air-cushioned shoes)
or ground surface (e.g. PU or wooden surface) may decrease the initial impact
effect of lateral heel flare
common used in jogging shoes because the heel flare increases base of support of the heel, resulting in decreased impact force
per unit area at the moment of initial contact
Heel flare shifts the initial contact point laterally,
which increases length of the moment arm (lever arm) and then increase amount of ankle moment.
This increase in ankle moment facilitates rapid pronation of the subtalar joint at the moment of landing,
decrease the possibility of lateral ankle sprain
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Takeoff
the greater the power of the leg drive, the greater the acceleration of the runner (F = ma)
to make the foot act as a rigid lever to propel the body forward through
supination of the subtalar joint
locking of the midtarsal joint
dorsiflexion (extension) of the MP joint of the big toe
impulse = F ´ t
= m ´ a ´ t
= m ´ v
= momentum
since running is a forward motion of the entire body, the horizontal component of the momentum is
much more important than the vertical component
momentum¡G a product of mass and velocity
momentum = mv
impulse-momentum relationship¡G any changes in momentum equals to the impulse that produced it
concentric contraction of the gastrocnemius muscle
the moment arm of the Achilles tendon increases during takeoff
moment of inertia is greatest at take-off during the entire running cycle
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Swing phase
the larger distance the body will move during swing phase depends on
less angle of takeoff
higher speed of body projection at takeoff
less difference in the height of COM at the moment of takeoff and landing
reduce the moment of inertia by lifting the knee and the hip close to the body
increase ROM of the lower extremity to bring the mass of the swing leg close to the hip and
increase the angular velocity of the swinging leg
moment of inertia
definition¡G the property of an object that causes it to remain in its state of either rest or motion
(Hamilton & Luttgens, 2002)
I = I0 + Ar2
where I0 = I about centroid axis
A = area
r = distance
moment of intertia about centroid axis at different fixed-shape objects
circular area:¡G I0 = (1/4) p r2
rectangular area¡GI0 = (1/12) b h3
traingular area¡G I0 = (1/36) bh3
example¡G determine moment of inertia around centroid axis of a T-shaped beam
 |
I = S I0 + Ar2
= [(1/12)(2)(10)3(2)(10)(8.55-5)2] +
[(1/12)(8)(3)3(8)(3)(4.45-1.5)2]
=645.6 |
According to Newton's first law of motion,
force is needed to change the velocity (amplitude and direction) of an object.
moment of inertia is greatest at take-off and least after acceleration has ceased
clearance of the foot from the ground is completed by
ankle dorsiflexion
knee flexion
hip flexion
distance of a body moving in the air depends on
the angle of take-off i.e. ths distance of the body COG ahead of take-off point
the speed of the body projection at take-off
the height of the COM at take-off and landing
muscle activities of the lower extremity during swing phase
| |
joint motion |
force for movement |
muscle used |
| hip |
flexion |
muscle |
iliopsoas + rectus femoris (concentric) |
| knee |
first 2/3¡G flexion
last 1/3¡G
extension |
first 2/3¡G
momentum
last 1/3¡G muscle |
first 2/3¡G --
last 1/3¡G hamstrings (eccentric) |
| ankle |
dorsiflexion |
muscle |
tibialis anterior + toe extensors (concentric) |
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Special Considerations in Sprinting
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Definition
running distance < 400 m
stance phase of sprinting is only 22% of the running cycle
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Efficiency of running -- to get maximum horizontal velocity without falling
increase in stride length
speed = stirde length ´ stride frequency
stride length is dependent on leg length, angle of hip raising, and strength of the leg extensors
stride frequency is dependent on speed of muscle contraction and the skill of runnerDuring the acceleration phase of the race, the trunk is more erect so
that the length of the stride increase dependent on the angle that the hip
joint raises
decrease in vertical displacement of the COM
Given the same ground reaction force, the smaller the vertical component of the leg drive,
the the greater the horizontal component of running velocity
foot strike close to center of gravity
better to use midfoot or forefoot strike in order to have line of gravity passing through the ankle joint
If the foot strikes ahead the line of gravity,
the ground reaction force creates a upward and backward moment that will retard forward motion.
Therefore, as the running speed increases, the distance between the
contact point of foot strike and the center of gravity decreases in
order to reduce the stance and facilitate propulsion.
If the foot strikes behind the line of gravity,
the ground reaction force create a upward and forward moment that will make the body fall forward
decease in lateral movements
motions occurring in the entire lower extremity should be in the sagittal plane
the arm movement is used to counterbalance rotation of the pelvis only
shortening of swing leg
the shortening of swing leg shortens the moment arm to decreases moment of inertia and increase forward velocity
the higher the knee lifts, the greater the velocity is created.
decrease internal resistance from the viscosity of the soft tissues
warm-up and stretching exercises can reduce the viscosity of the soft tissues of the participating limbs
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Sprint start
crouching start (ÃÛ½õ°_¶])
the greater the power of the leg drive, the greater the acceleration of the runner (F = ma)
assistance of starting block (°_¶]¬[)
make it possible that trunk inclines forward without overstretching the Achilles tendon
provides a tilting surface against which the foot pushes horizontally while using total hip, knee, and ankle extension
the horizontal push-off force (impulse) results in an increased horizontal velocity (momentum)
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Biomechanics of Jogging
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Definition
running > 1500 m
classification of long-distance runners (Brody, 1980)
jogger¡G run 3-20 miles per week at a rate of 9-12 minutes per mile
sports runner¡G run 20-40 miles per week and participate in "fun runs" or races of 3-6 miles
long-distance runner¡G run 40-70 miles a week at a pace of 7-8 minutes per mile and may compete in 10,000 m races or marathons
elite marathoner¡G run 70-200 miles a week with a pace of 5-7 minutes per mile
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Characteristics of jogging
stance phase decreases to 31%
should prevent repetitive impact stresses
heel strike or midfoot strike
medial and lateral flares
better material for heel pad
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