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Base of support (BOS) The distance between an individual’s feet while standing and during ambulation, including the part of the body in contact with the supporting surface and the intervening area. The normal BOS is considered to be between 5 and 10 cm.
Center of gravity (COG) The point at which the three planes of the body intersect each other. That point is approximately 2 in (5 cm) anterior to the second sacral vertebra in the human.
Step length The linear distance between the right and left foot during gait. Step length is measured as the distance between the same point of one foot on successive footprints (ipsilateral to the contralateral footfall).
Stride length The distance between successive points of foot-to-floor contact of the same foot. One stride is a full lower extremity cycle. Two step lengths are added together to make the stride length.
Cadence The number of separate steps taken in a certain time. Normal cadence is between 90 and 120 steps per minute.
Velocity The distance a body moves in a given time, calculated by dividing the distance traveled by the time taken.


Normal human gait is a method of bipedal locomotion involving the complex synchronization of the neuromuscular and cardiovascular systems.1


Walking involves the alternating action of the two lower extremities. The walking pattern is studied as a gait cycle (Figure 5-1). The gait cycle, which can be defined as the interval of time between any repetitive walking events, consists of two phases (Figure 5-1) and seven intervals (Figure 5-2). The major requirements for successful walking include the following2:

  • Support of body mass by the lower extremities.

  • Production of a locomotor rhythm—the stretch reflex and the extensor thrust.3 The stretch reflex is involved in the extremes of joint motion, while the extensor thrust may facilitate the extensor muscles of the lower extremity during weight-bearing.4

  • Dynamic balance control of the moving body.

  • Propulsion of the body in the intended direction.

  • Adaptability of locomotor responses to changing tasks and environmental demands.

During the gait cycle:

  • The swing of the arms is out of phase with the legs. Unless they are restrained, the arms tend to swing in opposition to the legs, the left arm swinging forward as the right leg swings forward and vice versa.4

  • As the upper body moves forward, the trunk twists about a vertical axis. The shoulders and trunk rotate out of phase with each other during the gait cycle.5 Although the majority of the arm swing results from momentum, the pendular actions of the arms are also produced by gravity and muscle action.4,6

  • The thoracic spine and the pelvis rotate in opposite ...

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