The walking stride below highlights the fact that when the lead leg heel has made contact with the ground, the leg is noticeably straight at the knee, and remains so when the entire foot is firmly planted onto the ground. This is further illustrated when the lead leg is in a vertical position. As the weight loaded onto the lead leg is distributed to the front of the foot (toes), the rear leg has pushed off, bent at the knee in readiness for the forward propulsion, and once it passes the vertical, begins straightening ready to heel plant for initial ground contact. Once the heel has been planted the rear leg toe contact with the ground expires. This cycle repeats and is the art of walking.
This stride pattern is the anatomical movement associated with bipeds. A lead leg does not bend at the knee in a walking stride.
The speed of this walking cycle can increase significantly, but within the same parameters of the above paragraph.
Contact with the ground is maintained at all times and there is no separation at this speed of walking.
During the course of a running cycle, it is clearly evident that the alternating lead legs are in a constant state of flex. There is no straightening of either leg during any part of the movement. Speed has rapidly increased and separation from the ground is continuous as the legs alternate from lead to rear positions.
A significant decrease in pace with the same knee flex and ground separation within the gait is either a slow run or a jog. This action is clearly not walking.
The quickest form of walking is commonly known as race walking (speed walking, power walking.)
The movement of this faster form of walking (shown below) clearly imparts the same principles as general walking, but offers a significantly quicker speed.
These basic principles are a straightening of the lead leg on heel contact with the ground and through the weight load onto the base of the foot through to its vertical positioning; and no separation from the ground as the rear toe lifts once initial contact is made from the lead heel.
Generally speaking, bipeds do not anatomically walk with both legs bent at the knees as they switch lead legs during the course of a walking cycle. This is an unnatural action, and perhaps only observed in the very elderly that are not able to sustain entirely straight legs during the course of their stride pattern.
This particular walking cycle in a sport should not occur, unless it was a deliberate action as a means to propel the body forward with the intention of increasing the speed variant.
This action at a higher speed gives the impression that the person has undertaken a lower sense of gravity and (to the naked eye) that there has been no separation from the ground. This is not the case.
In conclusion – a natural walking stride gait has a lead leg that straightens on impact and remains straight until it passes the vertical position. The rear toe does not lift from the ground until the lead leg heel plants.
The quickest form of walking – race walking – applies the same principles.
All occurrences of running and jogging have the two constants – a lead leg that is bent on impact, and a separation from the ground.