So far we did not speak about the stride length, which is defined as the distance between two successive placements of the same foot, but it is the parameter that will determine whether the gait is slow, medium or fast.
In our study we will consider that stride length will be determine by the following parameters:
- Rotation of the pelvic in the Horizontal plane ;
- Thigh/Hip flexion in the Sagittal plane;
Figure 1 provides some values and consequences on toe-off/pre-swing phases.
Figure 1 Large spectrum of human gaits according to the stride length.
Indeed for small stride length values, it means the pelvic does not rotate too much and there is more or less no flexion of the Hip:
- In "Terminal stance" phase, it is not necessary for the foot of the supporting leg to achieve a “heel rise”. A simple dorsiflexion will be enough to put the heel of the contralateral leg in contact with the ground;
- In the “Pre-swing” phase, the foot of the supporting leg, will start to rise its heel, keeping its forefoot on the ground;
- Finally at the beginning of the “Initial swing”, the "toe-off" will turn into "forefoot off”.
At the opposite for large stride length values:
- In « terminal stance » phase the stride length value is so large that only the forefoot of the supporting leg will stay in contact with the ground;
- Therefore in the “pre-swing” phase the foot of the supporting leg will be in contact with the ground through the big toe ;
ODOI will implement at the beginning gait with small stride length values. Indeed it will ne more easy to implement because it simplifies greatly the coordination Ankle, Knee, Hip.