Walking in Pictures

The walk usually starts with the feet at the "extended position," where the feet are farthest apart and the character’s weight shifts to the forward foot.
As the weight of the body is transferred to the forward foot, the forward knee bends to absorb the shock. This is called the "recoil position," and is the lowest point in the walk.
Halfway through the first step, the forward knee straightens out and lifts the body to it’s highest point. In this "passing position," the free foot passes the supporting leg.
As the character moves forward, the weight-bearing foot lifts off the ground at the heel, transmitting the force to the ball of the foot. The body starts to fall forward. The free foot swings forward like a pendulum to meet the ground and catch the body’s weight.
The free leg makes contact with the ground, completing half the cycle. The second half is an exact mirror of the first. If it differs, the character may appear to limp.

When the feet are fully extended, the hips rotate along the axis of the spine. To keep balance, the shoulders swing in the opposite direction. From the front, the spine looks relatively straight. But from the top, you can see the hips and shoulders twist in opposite directions.
At the passing position, the front view shows the weight of the free leg pulling the hip out of center, causing a counter-rotation in the shoulders. From the top, however, the hips and shoulders are nearly parallel.
At the extension of the second leg, the hips and shoulders again are flat when viewed from the front. From the top, however, you can see the completed rotation of the hips and shoulders.
Because walking is kind of like falling forward, the body should be angled forward slightly at the hips for most walks. The spine will arch up slightly to keep the chest and head over the hips. However, this line of action can change with the character’s attitude.