Bio Mechanics of Running

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


•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


•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


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

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• (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

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)


Run (3.2 m/s)


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

Bio Mechanics of Running

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