Under the Standard Model, the feet are flattened and placed sole-down on the ground. Early on, the ankles are fixed in neutral position – not too pronated or too supinated – and function like oblique hinges.
Figure 1. Standard Model view of the bones of the foot from above.
Under the Spiral Model, the feet form dynamic, three-dimensional spirals. They rotate around a central axis that runs from the outer tip of the heel through the ankle joint to the inner tip of the big toe.
Figure 2. Spiral Model of the foot showing the spiral structure and rotational axis.
Under the Standard Model, the inner arch is the key to the foot’s functioning, compressing to store energy and recoiling to release it again. The arch stiffens the foot at the end of each step so it can be used as a lever, pushing backwards to propel the body’s mass forward.
Figure 3. The arches of the foot from below.
Under the Spiral Model, all 26 bones of the foot form a spiral structure that rolls inward around its long axis with each step, like a cresting wave. Unlike the passive compression of the arch under the Standard Model, the spiral functions like a torsion spring.
Figure 4. The three-dimensional spiral structure and rotational axis of the foot.
When both feet are rolled inward against each other at the body’s midline, their arches meet in a structure called the Vault, the most stable foundation for the body that the feet are capable of forming.
Figure 5. The Vault, a stable structure formed by the countervailing inward rotation of the spiral frameworks of the feet.
No general guidance exists for foot development, and under the Standard Model development is left largely to trial and error, with intervention in cases of extreme pronation or supination to reduce the risk of chronic problems later on.
Figure 6. Foot classification showing high (supinated), neutral, and low (pronated) inner arch.
The Spiral Model relies on the Counterspiral Mechanism – nature’s symmetry-based development engine. The mechanism is activated when the feet’s spiral structures are rolled inward against each other at the body’s midline, producing a countervailing force that slowly repositions the bones of the feet into their spiral structures, and then stretches muscle and connective tissue over the resulting framework.
Figure 7. The Counterspiral Mechanism. The feet are clenched and inverted, with their lateral edges anchored close to the extended midline, then rolled inward against each other symmetrically.
Standard and Spiral
Both the Standard Model of biomechanics and the Spiral Model proposed here are based on the same conceptual framework for human gait, the inverted pendulum model. This model relates the motion of the legs to the swing of a pendulum, a mechanism renowned for its efficiency.
Figure 1. Inverted Pendulum Model.
To produce motion under the Standard Model, the stance foot plantarflexes, pushing down and back into the ground like a lever, while the swing leg flexes at the hip, lifting the leg and driving the next foot forward.
Figure 2. The axes of the ankle complex, with reference to the sole of the foot.
To produce forward motion under the Spiral Model, the swing foot clenches and inverts while the hip rotates back and in, as if to place the heel on the extended midline behind the stance foot. At the same time, the stance foot pushes sideways with its outer edge to rotate the foot’s spiral structure inward from heel to toe, like the roll of an ocean wave. These coordinated movements pull the stance hip back while driving the swing hip around the midline to position the swing foot for the next step.
Figure 3. Spiral Motion. Placement and motion of the right foot through a single stance phase.
In practice, Standard gait is much less efficient than predicted by the inverted pendulum model. The body’s mass must be transferred from leg to leg to sustain motion, but most of the energy is wasted during transitions or dissipated in the bones and soft tissues of the body as they absorb the shock of impact.
Figure 4. Standard Model of gait, an inverted pendulum model adjusted to accommodate the transition between pendulum-like steps with the addition of a double support phase.
Spiral gait is much more efficient than Standard gait. As the feet spiral back and forth in symmetry, their push and pull rotation of the hips around the midline becomes cyclical, eliminating the cost of vertical impulses and transitions from leg to leg. The center of mass coasts over the midline in a smooth, continuous motion.
Figure 5. Foot-Hip Connection. As the right foot completes its inward roll, it drives the left hip forward in an arc around the midline.
According to the Standard Model, the hands and feet share the same basic skeletal plan, but divergent evolution has made them functionally different. Like the feet, the hands are flattened and placed sole-down when used in a load bearing capacity. They have arches that mediate between mobility and stability, and the wrists function like oblique hinges.
Figure 1. Right hand, palm side view, splayed for placement under the Standard Model.
Under the Spiral Model, the functioning of the hands parallels that of the feet, similarly forming dynamic three-dimensional spirals that rotate around a central axis, here running from the outer wrist to the inside tip of the thumb. The spiral construction is key to both the efficient application of force with the upper body and the manipulation of tools and objects.
Figure 2. The right hand wrapped around its rotational axis according to the Spiral Model.
The Standard hand is capable of performing a remarkable variety of actions, from supporting the body’s weight against the ground to playing the piano. The most frequent daily use is simply to grasp objects. A number of different classification systems exist for over 30 identified grip types, but most fall into either the power or precision grip categories.
Figure 3. Taxonomy of grasps classified and depicted according to thumb position, hand and finger configuration, and grouped into power, precision, and intermediate grips.
Under the Spiral Model, when bearing load the hands are first clenched and inverted to position the outer wrists beneath the shoulder joints. The outer edges of the hands make contact with the ground, and each hand rolls inward across its transverse arch from pinky to index finger, with the thumb simultaneously rotating under the wrist to form a stable three-dimensional spiral structure.
Figure 4. Hand placed for bearing load.
Under the Spiral Model, the opposable thumb enables rotation and counter-rotation of the hand’s spiral framework around its central axis. A fully developed hand can activate a mechanism called the Spiral Seesaw, alternating application of down-spin at either end of the rotational axis. This spiral grip helps to optimize both power and precision in manual activities, manipulating torsion and spin for the most efficient tool use.
Figure 5. Spiral Seesaw, showing alternating strokes produced by applying down spin at either end of the hand’s rotational axis.