The Importance of Trunk-Pelvis Disassociation

The importance of generating effective and safe rotational power in sport is a critical component to athletic success. To develop rotational power, it is vital that the athlete first have the ability to disassociate the trunk (torso and shoulders) from the pelvis. Before we talk about trunk-pelvis disassociation, let’s define what this term means. Disassociation is “the disconnection or separation of something from something else or the state of being disconnected.” This essentially means the trunk or pelvis is moving independently from each other. Think of Tiger Woods when he swings a golf club, his trunk is almost turning 180 degrees while his hip (pelvis) is completely stable with no change in position.

When the trunk rotates independently from the pelvis the body is creating torque throughout the kinetic chain and when the body is done rotating it releases energy in a sequencing pattern from the feet to the hands. This allows the athletes to generate large amounts of force with little wasted energy. If the trunk and pelvis can’t move independently from each other then the athlete will not generate force very effectively in a rotational manner. Think of a tether ball pole. As the ball completely twisted around the pole it releases the ball back in a forceful manner because the base is secure. Now think of the tether pole being on a Lazy Susan, (inability to disassociate) when the ball is struck it will rotate but never fully rotate because the pole and ball aren’t dissociating from each other and torque isn’t being created. The ability to disassociate allows torque to develop within the muscles and released in the opposite direction.

If an athlete is struggling with disassociation. Two things must be looked at first: is it a mobility or stability issue. Below are some assessments that (TPI) Titleist Performance Institute uses to evaluate stability and mobility issues in trunk-pelvis disassociation.

  • The Lower Quarter Rotation Test: The objective of this test is to evaluate rotational mobility of the lower body. It’s essential for the athlete to have both internal/external rotation at the hip and tibia, as well as inversion/eversion at the ankle. Here’s a link to performing the test.

  • Seated Trunk Rotation Test: The objective of this test is to evaluate rotational mobility in the thoraco-lumbar spine. An inability to rotate the thoracic spine, can cause excessive lumbar spine rotation forces or over use of shoulder joint to compensate for lack of mobility. Here’s a link to performing the test.

By applying these assessments to your athletes, it may help you identify areas that your athletes need to focus on to improve rotational power. The ability to coordinate the separation of the trunk and pelvis in a rotational manner is vital to performing safe and effective rotational movement. Make disassociation a part of your program with all rotational movements to help improve rotational performance in your athletes.

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