02/27/2025
The Walking Sequence
In Posture Reflexes
This presentation depends on three basic laws:
Every action requires a balancing reaction
The center of gravity must remain over the center of support to remain upright.
Muscles only pull, they do not push.
It is well established that muscles do not work alone but in sequence with other muscles to accomplish point (1)
Two illustrative names for that are kinetic chain and anatomy train. The chin is a good illustration because if pushed the links just bunch together so it only works for pulling. The train is a good illustration because individual links can couple together and uncouple to connect to another unit and follow different track.
A reflex is an automatic sequence of such connections until the action is balanced by something that can push back like the ground. Podiatrists call it the ground force. Muscles pull on each other and on bones and bones can push but they cant pull on their own. Let us use a known reflex with the train illustration so that you can feel it in action. It is called the grasping reflex and you may have learned it by placing a finger in the palm of a baby and having it grasp your finger.
Place the back of the fingers in the palm of the other hand so that the hands hook together much like the units of a train couple together. You may feel the automatic reflex lock the hands together and if you push, pull, twist the grip tends to get stronger. You may have to send the message “straighten the fingers” to get them to instantly uncouple.
This is the kind of programming that is built up in our neuromuscular system to do a complicated task such as walking on two legs. There are pre actions built into the actions we are more conscious of so that the initiating action balances the action ordered. So we will start with one although there are many pre actions that have stabilized this action.
The Latissimus Dorsi pulls the humerus into extension and a rotational pull on the dorsi of the spine while the Psoas is pulling on the transverse processes of the spine to pull the femur into flexion. This helps with point (2) the anterior/posterior balance over the center of support but it also initiates another action rotation of the vertebra to that side. This turns the lateral bodies of the vertebra of T12/L1 where the Psoas Minor originates into alignment with its insertion on the ramus of the p***s above the hip socket. The Psoas Minor can then curve the spine anterior lateral and with it the center of gravity over the hip socket at the time of foot contact.
The train continues to pull from the ramus of the p***s to the distal medial femur and couples with the plantaris to the heel. Now the train meets something to pull against that will push back. The diagonal pull from the spine to the ground force creates a medial pull but also has the leverage to cause an external rotation of the foot therefore an ascending pull against the ground force is needed as a balancing reaction.
Ground contact of the big toe enables the oblique head of the Adductor Hallucis that counters the rotation force against the ground and starts an ascending force to the medial metatarsals which couples with the tibialis posterior which couples with the popliteal to the lateral distal femur as a counter force to the plantaris and stabilizes the knee.
The transverse head of the Adductor Hallucis pulls on the distal metatarsals and the train can take one of two possible tracks to ascend back to the spine. If the center of gravity is lateral it works synergistically with the brevis muscles to pull against the ground force to the posterior fibula and from the fibula to the iliotibial band to the lateral gluteal to the quadratus lumborum to the spine. If the center of gravity is medial the metatarsals are dorsiflexed pulling on the anterior fibula and iliotibial band to the tensor fascia femoris and the anterior line to allow the center of gravity to travel more lateral.
There are many more connections and variations but that is the basic design and I believe in a designer that made many adaptations possible. But we have not finished the step.
As the leg reaches maximum extension and the ankle maximum dorsiflexion the plantaris and popliteal become synergistic with the gastrocs and hamstrings to flex the knee which brings us back to the beginning. The triggering signal seems to be in the Soleus muscle which is more fibrous than muscular. To observe this: with the person supine legs straight push on the plantar surface of the forefoot to maximum dorsiflexion and observe if there is a knee flexion reflex,
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