Sway with Foot Rise

We’ve previously explored how Sway, without Foot Rise, risks imbalance during rotation. You can review that analysis here

Now let’s explore what happens when Foot Rise is added — and why it changes everything.

The Big Idea

When the Leader initiates a Natural Turn (or any figure involving sway combined with foot rise), the system transitions from a simple pendulum to an energy-stabilized gyroscopic maneuver.

This is the biomechanical version of "Why This Works, Every Time."

Key Principles

1. Progressive CBM

  • The Leader should not try to complete rotation "on 1."
  • Instead, CBM must occur as a smooth curve —
    a progressive dθ/dt over the 3 beats of the figure.
  • This delays peak torque and gives the Follower time to respond.

2. Sway as COG Compensation

  • The leg swing generates outward force.
  • Sway acts like a counterweight — keeping the Center of Gravity (COG) over the Center of Support (COS).
  • It’s dynamic feedback: sway grows in response to the leg’s torque.

3. Foot Rise as an Energy Injector

  • Foot rise lifts the system vertically, reducing vertical load briefly.
  • This reduces static friction just enough to increase turning speed.
  • It also compresses the required radius for the turn.

Supporting Math

Torque Cancellation:

\[ T_{\text{leg}} + T_{\text{sway}} \approx 0\]

If sway matches the torque created by the leg extension, the net tipping moment is canceled.

Vertical Force Reduction via Rise:

\[ F_z = mg - F_{\text{rise}}\]

Where:

  • \(mg\) = dancer’s weight
  • \(F_{\text{rise}}\) = force applied during foot rise

Less pressure = more maneuverability.

Increased Rotational Energy:

\[ E_{\text{rot}} \propto I \cdot \omega^2\]

Where:

  • \(I\) (moment of inertia) drops slightly due to foot rise and narrowing base.
  • \(\omega\) (angular velocity) therefore increases, helping rotation.

🟢 Why This Cannot Fail

  • The sway ensures balance.
  • The rise adds energy.
  • The progressive CBM times it correctly.
  • The Follower is carried, not dragged.

This is a self-stabilizing, biomechanically justified system.

✅ No awkward shove on beat 1.