Section 2, Chapter 3, Walking in a straight line

We will now explore the movement, the geometry, and the timing involved in simple walking. The walker may roll over the heel or push off from the ball of the foot. To simplify the initial analysis, we assume that the ankle does not move so that the foot will not swivel to adjust to the surface.

Let us assume that we are in the middle of walking, and that the left foot is about to go forward. This is step 1 of the action. There is simultaneous action on both the left-side and the right-side.

There are several components to the action on the left side:

Unweigh the left foot, which is to the rear of the hip by bending the knee on the left side to slightly raise the foot
Rotate at the hip on the left side to bring the knee forward
Rotate at the knee to bring the left foot forward until the leg is almost straight

There are several components to the action on the right side:

Put the full body weight on the right foot, which is to the front of the hip
Rotate at the hip on the right side to bring the body over the foot until the right foot is behind the hip

At this moment the second step of the action repeats the first step in a symmetric or mirror-image sequence.

There are several components to the action on the right side:

Unweigh the right foot, which is to the rear of the hip by bending the knee on the right side to slightly raise the foot
Rotate at the hip on the right side to bring the knee forward
Rotate at the knee to bring the right foot forward until the leg is almost straight

There are several components to the action on the left side:

Put the full body weight on the left foot, which is to the front of the hip
Rotate at the hip on the left side to bring the body over the foot until the left foot is behind the hip

Walking is a rhythmic activity. Step 1 and step 2 in sequence make a measure that can be repeated. Each of the steps can be seen as a beat in the measure. Each beat can be further subdivided to help with the timing of the sub-components.