Guide — Force Plates

Ground Reaction Forces

Newton's Third Law applied to the golf swing.

Before the club can move fast, the body must move fast. And before the body can move fast, it must interact with the ground. Newton's Third Law states that for every action, there is an equal and opposite reaction. In golf, the force you apply to the ground (Action) dictates the force the ground applies back to you (Reaction) to rotate your body.

The Three Vectors of Force

Using dual force plates, we measure GRF across three dimensions:

1. Horizontal (Lateral) Force

The side-to-side force. During the backswing, elite players apply force away from the target to shift their center of mass. In transition, they aggressively apply lateral force toward the target to initiate the downswing.

2. Torque (Rotational) Force

The twisting force that opens the hips and chest. It is created by applying force in opposite directions with the lead and trail feet (e.g., lead foot pushes forward and left, trail foot pushes backward and right).

3. Vertical Force

The up-and-down force. This is the largest magnitude of force in the swing. As players approach impact, they push aggressively into the ground (often exceeding 200% of their body weight). The ground pushes back up, causing the lead leg to post up and rapidly rotating the pelvis.

Timing is Everything

Peak forces must occur in a specific order for optimal energy transfer into the kinematic sequence:

1. Peak Lateral Force (usually right at the end of backswing/start of transition)
2. Peak Torque Force (mid-downswing, shaft vertical)
3. Peak Vertical Force (just prior to shaft parallel in the downswing)

If your vertical force peaks too late (at impact), you will likely jump at the ball and flip the clubface.