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Biomechanics of Biomechanics of RunningRunning
RunningRunning•A form of locomotion•A modification of walking•Differs from walking in;
– One phase: neither foot is contact with the ground
– No phase: both feet in contact with the ground
RunningRunning
•All determinants of walking are prominent in running– Pelvic rotation
– Pelvic tilt
– Lateral motion of pelvic
– Motion of hip, knee, foot and ankle
Running – A Gait Running – A Gait CycleCycle
• Contact Phase
• Flight Phase
Contact Phase
•Support Phase
– One foot in contact with
ground
•Foot Strike-Mid Support-
Take off
Flight Phase•Swinging through the air• Increases with increased
running speed•Clearance of foot from
ground:– Ankle dorsiflexion– Knee flexion– Hip flexion
Running StrideRunning Stride
Running Running TerminologyTerminology
•Step length•Stride
length•Foot strike
(heel strike)
•Cycle or stride time
•Stride rate
•Nonsupport phase
•Support phase (stance phase)
Mechanics of Mechanics of RunningRunning
•Stride length
•Arm action
•Center of gravity
•Speed/tension
•Foot position
•Knee action
•Hip action
•Support and
nonsupport
time
•Trunk angle
Step and Stride• Step
– The moment when foot terminates contact with the ground and continues until the opposite foot contacts the surface
• Stride– The termination of contact of foot
with the ground through the next contact of the same foot
– 2 steps
• Take off distance– Horizontal distance that CG is FW
of toe of take off foot when leaving the ground
• Flight distance– Horizontal distance that CG travels
while in the air• Landing distance
– Horizontal distance that toe of leading foot is FW of CG at landing
Stride LengthStride Length
Stride LengthStride Length
•Depends on:
– Leg length
– ROM of hip
– Strength of leg extensors
Stride FrequencyStride Frequency• Number of strides athletes
takes in a given time
•Depends on:
– Speed of muscle contraction
– Skill of running
•Regarded as the sum of – Time during contact the ground
– Time spent in the air
•Ratio– 2 : 1 during start
– 1 : 1.3 and 1 : 1.5 at max speed
Stride FrequencyStride Frequency
• Speed of the run = SL x SF
where; SL = Stride length
SF = Stride frequency
(Hoffman;1971, Teeple; 1968,
Sparks; 1974)
Relationship between Relationship between SL and SFSL and SF
• Long stride + high frequency = fast runner
• Short stride + low frequency = distance runner => conserve energy
• Men 4.87 m (16ft) 5 steps/s• Women 3.65-4.26 m (12-14 ft) 4
steps/s
Relationship between Relationship between SL and SFSL and SF
•Very close relationship between height and SL– SL = 1.14 times of height– SL = 2.11 times of leg length
•SF decreases as height and leg length increase
•Average max SL = 1.24 times of height
Relationship between Relationship between SL and SFSL and SF
Foot PositionFoot Position•Depends on velocity of the run•The contact is first made :
– Heel strike the ground first better for long distance•Heel pad can absorb high impact force
•Midfoot strike (whole foot strike)
•Forefoot strike– Used in sprinting
Foot PositionFoot Position•Foot:
– Slight supination– External rotation of tibia
•To absorb impact in striking ground:– Rapid extension of hip– Internal rotation of tibia– Pronation of subtalar joint
Running EfficiencyRunning Efficiency•Decrease vertical
displacement of Center of Mass
•Foot strike close to line of gravity
•Decrease lateral movements
•Shortening of swing leg• Increase in SL
Skilled and Unskilled Skilled and Unskilled RunnersRunners
• At the beginning of flight phase
– Skilled runners have greater knee and hip flexion in leading limb
• At the beginning of contact phase
– Skilled runners have greater knee flexion of rear limb, bringing the heel closer to buttock
Skilled and Unskilled Skilled and Unskilled RunnersRunners
Foot PositionFoot Position
Stride LengthStride Length
TIME
DISTANCE AVERAGE SPEED
STRIDE LENGTH STRIDE FREQUENCY
STRIDE TIMELANDING DISTANC
E
FLIGHT DISTANCE
TAKE-OFF DISTANCE
SPEED OF RELEASE
ANGLE OF RELEASE
HEIGHT OF RELEASE
AIR RESISTANCE
TURN ON
GROUND
TIME IN AIR
SprintingSprinting
SprintingSprinting
SprintingSprinting• (a) On your marks• (b) Set
– Lift knee of back leg and elevate hips
– Shift CG forward
• (c-e) Go– Swing arms vigorously– Forceful extension of both legs
drives body forward
Sprint StartSprint Start•Crouch start places in position
to move CG rapidly ahead of feet– Bunch or bullet; foot length (10-12
inches)
– Medium; shank length-1/2 of front foot ( 16-21 inches)
– Elongated; shank length ( 24-28 inches)
Starting BlockStarting Block
Sprint Starting Sprint Starting MechanicsMechanics
• Block spacing vary from 11-15 inches according to leg length
• Front knee joint angle should be near 900
• Rear leg is near extension to apply max thrust
• The greatest horizontal force against blocks was exerted by rear foot
Sprinting in ActionSprinting in Action
Sprinter in ActionSprinter in Action• Foot strike on outside border of foot Foot strike on outside border of foot
near ballnear ball• Foot-down position with feet Foot-down position with feet
completely flatcompletely flat• Toes ready to leave surfaceToes ready to leave surface• Both feet are off the ground (non-Both feet are off the ground (non-
support)support)• Rear foot liftRear foot lift• Knee lift in frontKnee lift in front• High knee lift and long stride potentialHigh knee lift and long stride potential• Foot strikeFoot strike
Action of LegsAction of Legs• Supporting phase
– Foot lands to CG pass FW
• Driving phase– First phase ends to foot leave
the ground
• Recovery phase– Foot is off the ground and
prepare to next landing
Supporting PhaseSupporting Phase• Arrest athletes downward motion
• To allow to move into drive body forward and upward into next stride with min loss of momentum
• Increase flexion of hip, knee and ankle to cushion shock of impact
Driving PhaseDriving Phase
• To drive or thrust downward and
backward against ground
• Extensor muscles of hip, knee
and ankle exert force in
determining body’s velocity at
“take off”
Recovery PhaseRecovery Phase
•Bring foot forward from
behind to the point at which
makes next contact
Action of ArmsAction of Arms• Contrary reactions in upper body
due to rotary actions of hips
• Flex arm at elbow and swing bw, fw and slightly iw
• Fw limit; shoulder height
• Bw limit; behind hip
Action of TrunkAction of Trunk
Middle and Long Middle and Long Distance RunningDistance Running
Middle and Long Middle and Long Distance RunningDistance Running
Muscle Activity in Muscle Activity in RunningRunning
•Glut. Max. & med. - active at the beginning of the stance phase (concentrically) and again at the end of the swing phase (eccentrically)
• Iliopsoas - active during a portion of the swing phase (concentrically)
Muscle Activity in Muscle Activity in RunningRunning
• Quadriceps -- 1st 10% of the stance phase (eccentrically) and last 20% of the swing phase (concentrically)
• Hamstrings -- initial portion of the swing phase (concentric) and at the end of the swing phase (eccentric)
• Plantar flexors (gastrocnemius & soleus) – Mid and latter part of stance phase
Elite Sprinter Elite Sprinter CharacteristicsCharacteristics
• Slight vertical displacement of body• Long length stride• Small amount of time on ground• Greater knee flexion during recovery
of leg• BW rotations of leg segment just
before foot contact• Strong and complete extension
during thrust phase of support
Running EconomyRunning Economy
• Comparing track and treadmill running;– Marathon-pace difference of 7-8%
at middle-distance pace
– 20% decrease in energy cost during draft
– Decrease in energy cost due to clothing and haircut
• Stride length in speed running depends on– It’s positively correlated with ratio
of leg length to body height
– It’s directly proportional to amount of force extended to propel body during running
– It’s inversely proportional to amount of braking force at touchdown
Running EconomyRunning Economy
Fatigue EffectsFatigue Effects• Lower CG during air phase• Greater FW body lean• Lateral extension of arms• Decreased leg lift• Shorter strides• Decreased step frequency• Wider base of support with legs
rotated laterally
Energy SourcesEnergy Sources
Walk (1.2 m/s)
Energy SourcesEnergy Sources
Run (3.2 m/s)
Energy SourcesEnergy Sources
Sprint (3.9 m/s)
•Divided into 4 phases
– Approach•Same as sprinting
– Takeoff
– Flight
– Landing
High HurdlesHigh Hurdles
High HurdlesHigh Hurdles
TakeoffTakeoff
• Bring up lead foot high under buttocks
• Swing lead knee fw and uw to reduce moment of inertia and facilitate rotation through hip
• Extending knee brings leading leg into near-straight position to transfer momentum to lower leg
• Actions of leading leg tend to;– Shift CG fw and uw– Body rotate bw and dw at the
same time• Distance of takeoff depends on
– Athlete’s height– Athlete’s leg length– Athlete’s speed and technique
TakeoffTakeoff
FlightFlight
• Lead leg and trunk continue to move fw
• Leading arm motion is fw and dw– CG clear hurdle as low as safety
• Leading knee cross hurdle– Motions of trunk and leg are
reversed
LandingLanding
•Body is nearly erect
•Drive vigorously fw into next running stride
•Tend to arrest bw rotation of trunk by movement of leading leg
Race Walking RulesRace Walking Rules• Support leg
must be straight when at heel-strike & remain straight through the vertical movement
• One foot must be in contact with the ground at all times
Analysis of Race Analysis of Race WalkingWalking
•Dorsiflexion increases at heel strike
•Hyperextension increases at knee in midstance
•Flexion increases at knee and hip during leg swing
•Pelvic rotation increases