Bio Mechanics Of Running

Biomechanics of Running

Running • 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

Running • 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 Cycle

• Contact Phase • Flight Phase

Contact Phase • Support Phase – One foot in contact with ground

• Foot Strike-Mid SupportTake off

Flight Phase • Swinging through the air • Increases with increased running speed • Clearance of foot from ground: – Ankle dorsiflexion – Knee flexion – Hip flexion

Running Stride

Running Terminology

• Step length • Stride length • Foot strike (heel strike) • Cycle or stride time

• Stride rate • Nonsupport phase • Support phase (stance phase)

Mechanics of Running

• Stride length • Arm action

• Knee action

• Center of gravity

• Hip action

• Speed/tension

• Support and

• Foot position

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

Stride Length • 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 Length • Depends on: – Leg length – ROM of hip – Strength of leg extensors

Stride Frequency • Number of strides athletes takes in a given time

• Depends on: – Speed of muscle contraction – Skill of running

Stride Frequency • 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

Relationship between SL and SF • Speed of the run = SL x SF where;

SL = Stride length

SF = Stride frequency (Hoffman;1971, Teeple; 1968, Sparks; 1974)

Relationship between SL 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 SL 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

Foot 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 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 Efficiency • Decrease vertical displacement of Center of Mass • Foot strike close to line of gravity • Decrease lateral movements • Shortening of swing leg

Skilled and Unskilled Runners • 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 Runners

Foot Position

Stride Length

TIME DISTANCE

AVERAGE SPEED

STRIDE LENGTH

TAKE-OFF DISTANCE

FLIGHT DISTANCE

STRIDE FREQUENCY

LANDING DISTANC E

SPEED OF ANGLE OF HEIGHT OF AIR RELEASE RELEASE RELEASE RESISTANCE

STRIDE TIME

TURN ON GROUN D

TIME IN AIR

Sprinting

Sprinting

Sprinting • (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 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 Block

Sprint Starting Mechanics • 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 Action

Sprinter in Action • Foot strike on outside border of foot near ball • Foot-down position with feet completely flat • Toes ready to leave surface • Both feet are off the ground (nonsupport) • Rear foot lift • Knee lift in front • High knee lift and long stride potential • Foot strike

Action 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 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 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 Phase • Bring foot forward from behind to the point at which makes next contact

Action 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 Trunk

Middle and Long Distance Running

Middle and Long Distance Running

Muscle Activity in Running • 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 Running

• 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 Characteristics • • • •

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 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

Running Economy • 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

Fatigue 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 Sources

Walk (1.2 m/s)

Energy Sources

Run (3.2 m/s)

Energy Sources

Sprint (3.9 m/s)

High Hurdles • Divided into 4 phases – Approach • Same as sprinting

– Takeoff – Flight – Landing

High Hurdles

Takeoff • 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

Takeoff • 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

Flight • 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

Landing • 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 Rules • Support leg must be straight when at heel-strike & remain straight through the vertical movement • One foot must be in contact

Analysis of Race Walking • Dorsiflexion increases at heel strike • Hyperextension increases at knee in midstance • Flexion increases at knee and hip during leg swing • Pelvic rotation increases