Golf Swing Kinetic Analysis Using Segmented Body Model

The golfer's body is divided into multiple rigid body segments (torso, upper arms, forearms, hands, thighs, lower legs, feet) connected by universal rotational joints. This segmentation allows the complex motion to be broken down into manageable components, each measurable by the optical motion capture system, while the force plates measure ground reaction forces at the feet. The segmentation principle resolves the contradiction by enabling precise measurement of individual segment kinetics without requiring a single overly complex measurement device.

A computer implements inverse dynamics calculations as an intermediary process between the raw measurements from optical sensors and force plates, and the final kinetic parameters. The computer processes positional data from markers and force data from plates, applies mathematical models of the segmented body, and computes joint forces, torques, and power. This intermediary computational layer integrates data from multiple simple devices to achieve precise kinetic measurement without requiring each individual device to be complex.

The system uses dynamic models of rigid body segments with universal rotational joints that can adapt to the actual motion throughout the golf swing. Rather than assuming fixed kinematic relationships, the dynamic model calculates joint forces, torques, and power at each instant based on measured accelerations and positions. This dynamic approach improves kinetic parameter accuracy by accounting for the actual time-varying nature of the swing, while the computer automation manages the calculation complexity.

The inverse dynamics calculations use feedback from measured ground reaction forces and segment accelerations to iteratively determine joint kinetic parameters. The system continuously refines the kinetic model by incorporating real-time measurement data, improving accuracy. The computer automation handles the iterative calculation complexity, allowing the feedback mechanism to focus on improving kinetic parameter precision rather than managing computational burden.

The body is segmented into standard anatomical regions (torso, limbs, segments) with predefined inertial properties and joint locations. This standardization allows detailed analysis without requiring custom modeling for each golfer, improving ease of operation. The segmentation enables accurate energy transfer analysis by tracking kinetic energy through each segment while maintaining a consistent, repeatable measurement protocol that is easier to operate than custom approaches.

The system uses a standardized computer model template that can be applied to different golfers without requiring complete remodelling. The rigid body segment model with universal joints serves as a reusable template that is adapted to individual golfers through measurement of their specific anthropometric data. This copying approach maintains high analysis accuracy through detailed segment modeling while significantly improving ease of operation by eliminating the need to create custom models for each subject.

The optical motion capture system and force plates are designed to serve multiple functions: they can measure individual golfers for coaching purposes, collect data from multiple players for database compilation, and analyze various aspects of the swing (kinematics, kinetics, energy transfer). This multi-functionality justifies the investment cost by maximizing the utility of each measurement device, allowing the system to pay for itself through comprehensive analysis capabilities that would otherwise require multiple specialized devices.

The system uses disposable or easily replaceable components such as reflective markers attached to the golfer's body and force plate inserts that can be recovered and reused. The markers are inexpensive and can be reapplied to different golfers, while the expensive force plate hardware remains intact and reusable. This approach allows the system to maintain high measurement precision through consistent use of calibrated equipment while minimizing the cost impact through selective replacement of only the consumable components.