Kinetic sequence & Peak windows: How GRF peaks act on the player’s swing and club?

In this article, we will focus on the global max peak of Ground Reaction Forces measured during a swing.

In review, the Ground Reaction Forces (GRF) exists to manage simultaneously body balance aspects and genesis of motion.

By looking at the global max peak of force generated by the player on lateral axis (lateral), around the vertical axis (rotation) and on the vertical axis (vertical), we can analyze the cause and effect of max peak of force on the motion of the “entire golfer system”, which means the body of the player, his body segments and the object is carrying in his hands, the golf club. When the GRF start increasing, it can affect the entire body displacement and / or some body segments displacements and / or the golf club displacement while maintaining whole system stability.

Please notice, all long the swing, the gravity is applied to the body and the club, which have a constant downward acceleration to the ground of Gravity force.

The peak of combine lateral force can have the following effects:

Change of direction of the club away from the target at transition, and first acceleration for the club in frontal plane / along the lateral axis. Amount and timing of peak varies depending on club type / specs, backswing length and club plane.
Shift the entire body from trail side to lead side, its amount varies depending on posting and individual GRF of each foot vector.

The peak of global Vertical Torque can have the following effects:

Bring the club from behind your back to be in front of you, with a second acceleration of the club in the horizontal plane. Amount and timing of the peak varies depending on club type / specs and plane.
Generate some horizontal rotational acceleration peak of body segments, most commonly the hips and / or trunk and shoulders. Moreover, when a player exhibits a high Anterior Posterior force opposite below his feet, the more opportunity is there to transform it in a high peak of body or body segments rotational velocity in the horizontal plane.

The peak of combined vertical force can have the following effects:

Provokes the release action of the club with important acceleration of the club head toward the ground, the third acceleration through downswing around the vertical axis in thee frontal plane. Amount and timing of the peak varies depending the club type / specs and plane, and wrist hinging
Tends to create the lower body leg extension, depending on the direction and length of the individual GRF vector under each foot. Improper timing in the vertical force peaks, under lead leg and trail leg can cause trouble and club delivery and impact, and on alignments between lower body and upper body. You can observe some spine angles between hips and neck that can be mostly generated by vertical GRF, which must always prevent the increase of risk of injuries…

Each peak of Ground Reaction Forces influences:

the body motion, and its ability to organize stability and produce stability by sequencing the body segments through time and space via the incredibly complex neuromuscular system.
the club displacement in order to accelerate the club all long downswing and reach its max club head speed at impact with the ball

By modifying the Ground Reaction Forces parameters, you’ll modify the body motion and consequently the club head motion and associate ball flight…

Jean-Paul FERNANDEZ – Sport Scientist

March 2020