The X factor term was coined by John Andrisani in Golf Magazine many years ago and became more popular thanks to Jim McLean when he published in 1992 his article “Widen the Gap”.
The X factor wants to describe the relation between upper body (UB) and Lower Body (LB), specifically the shoulders rotation compared to the pelvises rotation at the top of the backswing. If the data shows 90 degrees rotation of the shoulders at the top of the backswing and 45 degrees rotation of the pelvis, the X factor data will be 45 degrees, this is given by the difference between UB degrees and LB degrees.
This type of measurements are available just through the 3D systems, like electromagnetic, Optical, or inertial systems (like MySwing that I'm using to teach).
For many years the above mentioned was common knowledge and supported by many, included Mike McTeigue, who published an article stating that to create more speed, golfers had to increase as much X factor as possible.
Years later, Phil Cheetham came out with a research which made all the Golf Coaches think and analyze. He believed that by turning the pelvis first keeping the shoulders at the same angle, before starting the downswing, the golfer could have had more speed. He called the process “x factor stretch”.
Now we know that there are 3 main extra stretches that contribuite to create more angular velocity in the downswing:
- X factor stretch - Maximum x factor in early downswing minus the x factor pelvis in transit
- Lead arm adduction stretch - angle between the lead upper arm and the ribcage; The lead arm compresses into ribcage in transition. The left shoulder join is stretched and then rapidly released.
- Wrist lag stretch - angle between the fore arm and the shaft. We have 4 types of wrist lag stretch and one typical amateur wrist angle:
- Fixed set angle: the angle is maintained during the downswing and released just before the impact
- Downswing loading: the wrist angle decreases until the arm is parallel. This profile allows also to drop the club under the plane, creating the natural closing torque like Sergio Garcia.
- Pre release loading: the angle is maintain during the transition, but during the downswing the angle is decreasing just before release like Rickie Fowler, Vijay Singh.
- Release and reload: the wrist angle initially before the top is releases and then reloads just before release again like Rory Mcllroy. It seams non efficient, but it is.
- Casting: the wrist angle continuosly release from the top to the impact (typical in amateurs)
TPI analyzed these extra stretch to the founding that it applies mostly to skilled golfers, while it's hard to see in the average golfers. Thanks to the biomechanics's analysis we have learned that these extra stretches help the golfers increase the forces in the muscle form eccentric contraction, storing elastic energy and increasing the muscle force from the stretch reflex.
Here, you can find the average in degrees of the stretch of the Tour Players, men and women:
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