Normal Gait

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Normal Gait
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• Gait is the medical term to describe human
  locomotion, or the way that we walk.
  Interestingly, every individual has a unique gait
  pattern.

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Definition

• Physiological Definition
• It is a mechanism which depends upon closely
  integrated action of the subjects, bones, muscles
  and nervous system (including peripheral and
  central nervous system)
• The degree of integration determines the
  different gait patterns. Any defect of any part
  of them or all of them will lead to pathological
  gait.
• Mechanical definition
• It is a form of bipedal locomotion as there is an
  alternating action between lower extremities. One
  leg is in touch with the ground for restraining,
  supporting and propulsion.
• The other leg is in swing phase for creating a
  new step forward. So gait is the result of a
  series of rhythmic alternating movement of arms,
  legs, and trunk which create forward movement of
  the body.

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Prerequisites of gait

• There are (4) major criteria essential to
  walking.
• Equilibrium
• The ability to assume an upright posture and
  maintain balance.
• Locomotion
• The ability to initiate and maintain
  rhythmic stepping
• Musculoskeletal Integrity
• Normal bone, joint, and muscle function
• Neurological Control
• Must receive and send messages telling the
  body how and when to move.
• (visual, vestibular, auditory, sensori-motor
  input)
• Forces for gait
• Muscular force.
• Gravitational force.
• Forces of momentum.
• Floor reaction force.

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Gait cycle

• The gait cycle is used to describe the complex
  activity of walking, or our gait pattern. This
  cycle describes the motions from initial
  placement of the supporting heel on the ground to
  when the same heel contacts the ground for a
  second time.

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Phases of Gait
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Each gait cycle can be described in the phasic
terms.

• Stance Phase
• Is defined as the interval in which the foot is
  on the ground (60 of the gait cycle).
• Stance Phase is divided into
• 1)Heel strike to foot flat2) Foot flat
  through mid-stance3) Mid-stance through Heel
  off4) Heel off to Toe off.

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• The stance period consists of the first five
  phases initial contact, loading response,
  mid-stance and terminal stance.

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1) Initial Contact

• Initial contact is an instantaneous point in time
  only and occurs the instant the foot of the
  leading lower limb touches the ground. Most of
  the motor function that occurs during initial
  contact is in preparation for the loading
  response phase that will follow. Initial contact
  represents the beginning of the stance phase.
  Heel strike and heel contact serve as poor
  descriptors of this period since there are many
  circumstances when initial contact is not made
  with the heel alone. The term "foot
• strike" sometimes is used as an alternative
  descriptor.

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2) Loading Response

• The loading response phase occupies about 10
  percent of the gait cycle and constitutes the
  period of initial double-limb support. During
  loading response, the foot comes in full contact
  with the floor, and body weight is fully
  transferred onto the stance limb.
• The initial double-support stance period
  occasionally is referred to as initial stance.
  The term foot flat (FF) is the point in time when
  the foot becomes plantar grade. The loading
  response period probably is best described by the
  typical quantified values of the vertical force
  curve. The ascending initial peak of the vertical
  force graph reveals the period of loading
  response.

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3) Mid-stance

• Mid-stance represents the first half of single
  support, which occurs from the 10- to 30-percent
  periods of the gait cycle. It begins when the
  contra-lateral foot leaves the ground and
  continues as the body weight travels along the
  length of the foot until it is aligned over the
  forefoot. The descending initial peak of the
  vertical force graph reveals the period of
  mid-stance

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4)Terminal Stance

• Terminal stance constitutes the second half of
  single-limb support. It begins with heel rise and
  ends when the contra-lateral foot contacts the
  ground. Terminal stance occurs from the 30- to
  50- percent periods of the gait cycle. During
  this phase, body weight moves ahead of the
  forefoot.
• The term heel off (HO) is a descriptor useful in
  observational analysis and is the point during
  the stance phase when the heel leaves the ground.
  The ascending second peak of the vertical force
  graph demonstrates the period of terminal stance
  .
• Roll off describes the period of late stance
  (from the 40- to 50- percent periods of the gait
  cycle) when there is an ankle plantar-flexor
  moment and simultaneous power generation of the
  triceps surae to initiate advancement of the
  tibia over the fulcrum of the metatarsal heads in
  preparation for the next phase

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2) Swing Phase

• is defined as the interval in which the foot is
  not in contact with the ground (40 of the gait
  cycle).denotes the time when the foot is in the
  air, constituting the remaining 38 percent of the
  gait cycle. The swing phase could be defined as
  the phase when all portions of the foot are in
  forward motion.

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Swing is divided into two phases

• 1) Acceleration to mid-swing2) Mid-swing to
  deceleration
• The swing period primarily is divided into three
  phases initial swing, mid-swing and terminal
  swing. Pre-swing, however, prepares the limb for
  swing advancement and in that sense could be
  considered a component of swing phase.

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Pre-swing

• Pre-swing is the terminal double-limb support
  period and occupies the last 12 percent of stance
  phase, from 50 percent to 62 percent. It begins
  when the contra-lateral foot contacts the ground
  and ends with ipsilateral toe off. During this
  period, the stance limb is unloaded and body
  weight is transferred onto the contra-lateral
  limb. The descending portion of the second peak
  of the vertical force graph demonstrates the
  period of pre-swing.
• Terminal contact (TC), a term rarely used,
  describes the instantaneous point in the gait
  cycle when the foot leaves the ground. It thus
  represents either the end of the stance phase or
  the beginning of swing phase. In pathologies
  where the foot never leaves the ground, the term
  foot drag is used. In foot drag, the termination
  of stance and the onset of swing may be somewhat
  arbitrary.
• The termination of stance and the onset of swing
  is defined as the point where all portions of the
  foot have achieved motion relative to the floor.
  Likewise, the termination of swing and the onset
  of stance may be defined as the point when the
  foot ends motion relative to the floor. Toe off
  occurs when terminal contact is made with the
  toe.

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b) Initial Swing

• The initial one-third of the swing period, from
  the 62- to 75-percent periods of the gait cycle
  (6), is spent in initial swing. It begins the
  moment the foot leaves the ground and continues
  until maximum knee flexion occurs, when the
  swinging extremity is directly under the body and
  directly opposite the stance limb.

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c) Mid-swing

• Mid-swing occurs in the second third of the swing
  period, from the 75- to 85-percent periods of the
  gait cycle. Critical events include continued
  limb advancement and foot clearance. This phase
  begins following maximum knee flexion and ends
  when the tibia is in a vertical position.

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d) Terminal Swing

• In the final phase of terminal swing from the 85-
  to 100-percent periods of the gait cycle, the
  tibia passes beyond perpendicular, and the knee
  fully extends in preparation for heel contact.