GAIT

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GAIT 1BASIC PARAMETERS ANDGROUND REACTION
FORCES
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THERE ARE 4 EVENTS IN A GAIT CYCLE.THEY ARE THE
HEEL STRIKES (LHS RHS) AND THE TOE OFFS (LTO
RTO)
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THE HSs AND TOs DIVIDE THE WALKING CYCLE INTO
PHASES.ONE LIMB, AFTER HS, HAS SUCCESSIVE PHASES
OF DOUBLE SUPPORT, SINGLE SUPPORT, DOUBLE SUPPORT
AND SWING
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BY CONVENTION, A WALKING GAIT CYCLE IS USUALLY
CONSIDERED TO BEGIN WITH A HEEL STRIKE
(HS).THIS EVENT COULD BE LHS OR RHS
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THE JARGON OF GAIT(parameters on L
events/phases on R)

• STRIDE LENGTH
• STEP LENGTH
• SPEED
• CADENCE
• CYCLE TIME
• TIME OF SWING
• Relative stride length
• Relative speed

• HEEL STRIKE (L R)
• TOE OFF (L R)
• SINGLE SUPPORT PHASE
• DOUBLE SUPPORT PHASE
• SWING PHASE

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THE PHASES ARE PUNCTUATED BY THE EVENTS of heel
strike toe off
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TRY TO CONSTRUCT AND LABEL A SIMILAR CHART TO THE
LAST ONE WHICH WOULD DESCRIBE EVENTS AND PHASES
FOR RUNNING
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IF WE WALK VERY SLOWLY

• OUR NERVOUS SYSTEM CANNOT GENERATE A RHYTHMIC
  GAIT BELOW ABOUT 0.4 Hz ( 2.5s CYCLE TIME)
• THE GAIT DEGENERATES INTO A SERIES OF POSTURES

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IF WE WALK VERY FAST

• STRIDE LENGTH IS ABOUT TWICE OUR HEIGHT AND A
  SWING TAKING A MERE 0.3s
• HEEL STRIKE COINCIDES WITH CONTRALATERAL TOE OFF
  i..e. DOUBLE SUPPORT DISAPPEARS
• WE HAVENT ENOUGH MUSCLE POWER TO GO FASTER
• IT IS MORE ECONOMICAL TO RUN

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COMFY, ECONOMICAL or PREFERRED WALKING HAS
(roughly) - A CADENCE OF 120 A CYCLE TIME
OF 1sec REL. SPEED 1 stature/sec REL.
STRIDE stature TIME OF SWING 0.4sHOW LONG
IS DOUBLE SUPPORT?

• 1.

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TO INCREASE SPEED..

• 1. INCREASE STRIDE LENGTH
• 2. INCREASE STEP FREQUENCY
• 3. DECREASE TIME OF SWING

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USING A FORCE PLATE

• WHEN SOMEONE WALKS ON A FORCE PLATE, IT RECORDS
  THE FORCES ACTING UPON IT.
• ACTION AND REACTION ARE EQUAL AND OPPOSITE
  (NEWTONS 3RD LAW).
• THE FORCES UPON THE WALKER, EQUAL AND OPPOSITE TO
  THOSE UPON THE FORCE PLATE, ARE CALLED GROUND
  REACTION FORCES.

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FORCE PLATE MEASURES VERTICAL, LATERAL AND
FORWARD FORCES AT EACH CORNER
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GROUND REACTION FORCES (ON THE BODY) ARE EQUAL
AND OPPOSITE TO THE MEASURED FORCES ON THE PLATE
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LOCATING A CENTRE OF FOOT PRESSURE
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GROUND REACTION FORCES

• THE GRFs ACT UPON THE BODY THROUGH THE FEET.
• GRFs HAVE VERTICAL, LATERAL AND A-P COMPONENTS
• THE ONLY OTHER FORCE IS BODY WEIGHT (WHICH ACTS
  VERTICALLY DOWNWARDS)

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3-D viewofGROUNDREACTIONFORCES
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The net vertical force is the difference between
the GRF and body weight
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RETROPULSION PROPULSION
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Lateral force is opposite to the side of support
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NEWTONS 2ND LAW

• NET FORCE BODY MASS x ACCELN OF THE CENTRE OF
  MASS
• IN A COMPLETE CYCLE OF STEADY WALKING, THE
  INTEGRATIVE EFFECT OF NET FORCES x TIME CANCEL
  OUT
• IF THE IMPULSES DONT CANCEL, WE CHANGE SPEED OR
  DIRECTION

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COMING NEXT.

• 1. . MOVEMENTS OF LOWER LIMBS
• 2. USE OF ANGLE-ANGLE DIAGRAMS
• 3. MUSCLES THAT CONTROL AND PRODUCE
  MOVEMENT IN GAIT.

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THATS ALL FOR NOW