Stack & Tilt Worldwide

Motor control is the foundation of athletic motion. In golf, swaying or shifting mass away from the target during the backswing does not define athletic motion or skill. Data comparing three segments of a multi-segment system between mid-handicap golfers and the top four players in the world reveals a clear movement pattern that distinguishes expert players. Higher-handicap golfers tend to sway one, two, or all three segments farther away from the target and for longer periods than elite players.
Several important observations emerge from this data. Much of modern golf science has attempted to model the golf swing using a simplified Center of Mass (COM) and Center of Pressure (COP) framework, where torque is calculated around a generalized center of mass derived from ground reaction forces.
However, the golf swing is not a single-segment system. It is a complex multi-segment motion involving individual joints, rotational centers, and interacting torques throughout the body.

Connecting players and coaches around the world using a system for golf. Living the

Conflating Sway with “Athletic Motion”.
The image depicts the top four players in the world across the top of the page, as part of eight of the top ten players overall. The data shown represents 3 segments within a multi-segment biomechanical system: the pelvis, the chest (thorax), and the head. The measurements demonstrate a consistent pattern among elite players. The top players demonstrate little to no translation away from the target, while some move toward the target.
Several important observations emerge from this data.
First, much of modern golf science has attempted to model the golf swing using a simplified single-segment Center of Mass (COM) and Center of Pressure (COP) framework. In this model, overall torque is calculated around a generalized, overall center of mass derived from ground reaction forces. However, a golf swing is not a single-segment system. It is a highly complex multi-segment motion composed of individual joints, rotational centers, and interacting torques throughout the body.
As a result, torque in the golf swing should not be calculated around a generalized center of mass. Instead, torque must be understood through the individual centers of rotation associated with each segment and joint. The pelvis, thoracic, neck, shoulders, arms, and lower extremities all contribute distinct motions and torques that interact dynamically through time and space. A single COM/COP model cannot adequately measure these independent segmental movements and therefore lacks the capacity to accurately predict club delivery or ball flight.
Inexperienced researchers chose a poor modeling system for a multi segment system like golf. Athletic motion “experts”, fitness “experts”, and radar experts have used this poor model and routinely cited Sway, or shifting of the overall mass away from the target as an “Athletic Motion”. In fact, “Athletic Motion” in a multi segment system is not epitomized by sway. The motor control and coordination of joints segments that defines “Athletic Motion”. The COP/ COM model cannot recognize the motor control of the individual segments that creates this coordination.

This weeks Best Player, the winner of the PGA Championship , and major champion is Aaron Rai . His motion provides a compelling case study in early backswing mechanics.
From P1 to P2, he transitions from 8 degrees of side tilt toward the trail side to 25 degrees toward the lead side. This represent a 33 degree dynamic range of side tilt to the lead side within approximately the first 20 inches of the hand trajectory.
A few observations:
First, these measurements were generated by SportsBox AI, a platform founded by a pioneer in 3D motion capture. Notably, these values are derived from a 2D camera capturing the swing, yet producing 3D measurements. Historically, critics argued that extracting 3D data from 2D imagery was not feasible—particularly when Stack & Tilt first introduced this mechanical concept. At the time, those critiques often reflected limited understanding of 3D motion and human biomechanics. Today, however, similar methodologies are widely accepted, and notably, comparable criticism has not been directed at SportsBox AI.
Second, some groups—ranging from proponents of ground-reaction-force models to radar-based instruction advocates, as well as simplified “key-based” teaching systems and social media instructors—have suggested that the magnitude of side tilt in this phase is overstated. Yet, the data here indicates a clear 33 degree change within a very short segment of the motion.
Next it is worth noting, as shown in previous analyses, a significant repeatable pattern is emerging in lead side tilt. Within the first twenty inches of hand trajectory, the dynamic range of side tilt to the lead side is roughly 30- 40 degrees. More importantly, the actual measured value of lead side tilt is clustering near 25 degrees. This compared with a minimal pelvic sway suggests the motion is not incidental but indicates a predictable, similar, compelling rationale.

The motions of elite players provide a valuable case study in early-backswing mechanics. Pictured is a catalog featuring the top four players in the world and eight of the top ten players. Their movement patterns reveal several highly consistent biomechanical characteristics from P1 to P2.
First, a significant and repeatable pattern emerges in lead-side tilt. Within approximately the first 20 inches of hand trajectory, players demonstrate a dynamic range of roughly 30–40 degrees of side tilt toward the lead side, as shown in previous analyses. More importantly, the actual measured values fall within a remarkably tight range, clustering near 25 degrees of lead-side tilt. This consistency among elite players suggests the motion is not incidental, but rather a predictable characteristic of highly skilled swings.
Second, there is very little pelvic sway during this phase of the motion. Seven of the eight players measured demonstrate pelvic sway within approximately plus or minus one-half inch. This minimal lateral movement further supports the idea that elite players maintain highly organized segmental motion early in the backswing.
Some instructional groups—including advocates of ground-reaction-force models, radar-based teaching systems, simplified “key-based” instruction, and various social-media instructors—have argued that the magnitude of side tilt during this phase is overstated. Yet the data presented here indicates a clear 35–40 degree change occurring within a very short segment of the motion. This is not an isolated characteristic, but a repeatable pattern demonstrated consistently by expert players.
Finally, it is important to recognize that this catalog represents only two segments within a multi-segment system used to analyze the golf swing: the pelvis and the thorax, or ribcage. Many inexperienced researchers and instructors have attempted to explain the golf swing using a simplified single-segment center-of-mass or center-of-pressure model. (COM/COP) Applying a single-segment framework to a multi-segment athletic motion has led to significant misunderstandings regarding elite swing mechanics and, in many cases, has hindered player development.

Here it comes London! Bringing the ! Stack&Tilt Practice Days with Andy and expert coach Billy Irvine. The Half Day sessions are limited to four students and are designed for grinding in the details of the system on the range. That’s 4 hours, 4 people, and Stack&Tilt. The afternoon session is SOLD OUT. To enroll visit stackandtilt.com/events. Dm us with questions.

Connect players and coaches from around the world using a system for golf.