The knee must be straight from moment of heel contact until the support leg is in the vertical position (see figure below.) The knee is flexed in the recovery swing, since short pendulums swing faster. The point at which the rear leg starts to bend varies between individuals. The optimum point for it to bend depends upon structure, flexibility and strength of the athlete.

WATCH FOR: The lead knee swinging through high. This is often due to a habit carried over from running (see figure below). This wastes energy and may lead to legality problems.

WATCH FOR: Bent knee on heel contact. This is illegal. Causes are over striding in front of the body, inadequate quadriceps strength and tight or weak hamstrings.

WATCH FOR: The lead knee bending before the leg is vertically upright. This is illegal. For reasons as stated above. In addition, it may be caused by the athlete trying to walk at speeds faster than their fitness level can sustain.

FOOT ACTION
The heel strikes the ground first with the toes elevated, not flat footed. Once the foot has made contact, it rolls forward, keeping the toes off the ground until the leg is supporting the body’s weight. How long the toes are kept off the ground is directly related to the strength of the shin.

There is a push off with the calf causing the foot to roll to vertical, before leaving the ground. The foot of the swing leg is brought forward close to but not brushing the ground.

WATCH FOR: Landing flat footed or with the foot slapping too soon. This has a braking effect which wastes energy, shortens the stride, and may cause the knee to bend early. This may be caused by a lack of shin strength or lack of flexibility an/or mobility in the hips.