Normal Gait Characteristics

Stance Phase (Encompasses the entire period during which the foot is on the ground)

  - The stance phase of gait begins with initial heel contact (initial double stance) and ends with toe off.

 -  The major function of the lower extremity at this point is to absorb the impact forces associated with the foot striking the ground.

 -   Ankle dorsiflexors eccentrically contract to allow the foot to plantar flex as it is lowered to the ground.

 -  From this point a decelerative phase of preceding motion begins as quadriceps eccentrically contract, thus absorbing more energy.

  -  The center of mass (COM) is lowered to its lowest point as the body maintains a double stance with dual foot contact.

  -  Subsequent elevation of COM begins as both the hip and knee begin to extend.

  -  This knee extension occurs as a result of both inertia provided by the trunk and a small muscular      contraction of the quadriceps muscles at mid stance.

 -  The rate of progression of trunk movement is controlled primarily by eccentric contraction of the           plantar flexors.

-  At mid stance, the bodies COM has reached its highest point.

 -  At the late stance phase the plantar flexors begin to concentrically contract and subsequently accelerate the trunk forward.  It is interesting to note that the plantar flexors provide the largest mechanical work of any lower extremity muscle group during walking.

 -  At this point in the gait cycle, pre swing phase involves concentric contraction of hip flexor musculature.

 

 

Swing Phase (Encompasses the entire time the foot is in the air for limb advancement)
 

  -  Acceleration of the leg forward occurs both as a result of concentric hip flexor contraction and as a result of a pendulum affect created by gravity.

  -  The rate and degree of knee flexion is controlled by an eccentric contraction of the quadriceps as it continues throughout the first half of the swing phase. 
            

 -  Terminal swing phase knee extension occurs as a result of both concentric contraction of the hip extensors, causing the femur to posteriorly rotate, and the inertia of the foot/low leg complex moving forward.

 -  Eccentric contraction of the hamstrings slowly decelerates the foot/low leg complex at this point in the gait cycle.

  -  This deceleration produces a simultaneous acceleration of the trunk through kinetic energy transfer.  Again, it is interesting to note that this decelerative effect imparts a greater impulse in accelerating the trunk forward than does the initial push off mechanism.
 

 

Timing

  -  Variances exist is the distribution of timing of each phase of gait.

 -  Approximately 60% of the gait cycle involves the stance phase whereas the swing phase lasts for approximately 40% of the cycle.

  -  Timing for both total stance and swing phases are shortened as the velocity of gait increases.

   -  At the point in gait when double stance is omitted the individual has reached a running mode of propulsion.
 

                   
 

  Step vs. Stride
 -  Stride is described as the period from the initial contact of a particular limb to the point of initial contact of the SAME limb and is equivalent to one gait cycle.

  -  Step is described as the period from initial contact of one limb to the initial contact of the contralateral limb.  Therefore, there are two steps in each stride (or gait cycle).