Floor Reaction Force Heel Strike

Figure 1 21a shows the contact area when standing barefoot on both feet.

Floor reaction force heel strike.

This leads to an increased step height and prolonged swing phase. The contact area is much smaller than the area of the base of support. At the end of the heel strike and the loading response steps the longitudinal force inside each thigh s muscle was computed. The definition offered by perry 11defines heel strike initial contact as the moment when the foot just touches the floor.

The ground reaction force is distributed across the whole of the area of contact between the feet and the floor. All the elements of the muscle mesh intersected by the cross section plane contributed to the longitudinal force. It is synonymous with the stride length. In forefoot striking the collision of the forefoot with the ground generates a very minimal impact force with no impact transient.

For example if heel strike is the initial contact the gait cycle for the right leg is from one heel strike to the next heel strike on the same foot. This force sends a shock wave up through the body via the skeletal system. This is the ground reaction force generated when heel strike running in shoes. The gait cycle is the time interval or sequence of motions occurring between two consecutive initial contacts of the same foot figure 14 1.

Ankle dorsiflexion weakness results in a lack of heel strike and decreased floor clearance. In heel striking the collision of the heel with the ground generates a significant impact transient a nearly instantaneous large force. By eliminating the heel strike the runner has eliminated the impact peak and the initial slope of the rising force is now lower. While this definition is appropriate for normal gait it does not describe the typical heel strike in many impaired populations.

At the instant of heel contact there is zero force between the foot and the floor due to the fact that the heel strike is defined the moment when contact is generated but there is no force production at that time instant. Loading rate has decreased. Calf tightening or contractures due to a period of immobilisation or trauma will cause reduced heel strike due to restricted dorsiflexion.