Gait

Gait cycle:
Stance phase accounts for approximately 60 percent, and
Swing phase for approximately 40 percent, of a single gait cycle.
Each gait cycle includes two periods when both feet are on the ground. The first period of double limb support begins at initial contact, and lasts for the first 10 to 12 percent of the cycle. The second period of double limb support occurs in the final 10 to 12 percent of stance phase. As the stance limb prepares to leave the ground, the opposite limb contacts the ground and accepts the body's weight. The two periods of double limb support account for 20 to 24 percent of the gait cycle's total duration.
Stance phase of gait is divided into four periods: loading response, midstance, terminal stance, and preswing. Swing phase is divided into three periods: initial swing, midswing, and terminal swing. The beginning and and ending of each period are defined by specific events.

STANCE PHASE:
Loading response begins with initial contact, the instant the foot contacts the ground. (Normally, the heel contacts the ground first. In patients who demonstrate pathological gait patterns, the entire foot or the toes contact the ground initially.) Loading response ends with contralateral toe off, when the opposite extremity leaves the ground. Thus, loading response corresponds to the gait cycle's first period of double limb support.
Midstance begins with contralateral toe off and ends when the center of gravity is directly over the reference foot. (Note that this phase, and early terminal stance, the phase discussed next, are the only times in the gait cycle when the body's center of gravity truly lies over the base of support.)

Terminal stance begins when the center of gravity is over the supporting foot and ends when the contralateral foot contacts the ground. During terminal stance, around 35 percent of the gait cycle, the heel rises from the ground.

Preswing begins at contralateral initial contact and ends at toe off, at around 60 percent of the gait cycle. Thus, preswing corresponds to the gait cycle's second period of double limb support.

SWING PHASE
Initial swing begins at toe off and continues until maximum knee flexion (60 degrees) occurs.
Midswing is the period from maximum knee flexion until the tibia is vertical or perpendicular to the ground.
Terminal swing begins where the tibia is vertical and ends at initial contact.