Power Essentials Part 3: X-Factor Stretch
X-Factor Stretch is the third and final installment of the mini series covering power essentials in the golf swing. As I am a strength & conditioning coach and not a golf instructor, I just dealt with the body, obviously how you use the club is of critical importance too, but that is for someone else to write about.
X-Factor Stretch (XFS) and X-Factor (XF), are measures of the difference between torso rotation and pelvis rotation (shoulder turn and hip turn). XF measures the difference at the top of the back swing (see Part 2 above for more), and XFS measures the the increase in this difference during the transition from back swing to down swing.
XFS is accomplished by the pelvis rotating towards the target to begin the downswing before the torso. The pelvis may even begin to rotate towards the target while the torso is still completing the back swing. To illustrate this lets imagine a golfer turns their shoulders 90 degrees in the back swing and their hips 45 degrees. This would give them an XF of 45 degrees. If this player then started the downswing by rotating their hips towards the target by 10 degrees while the shoulders stayed in place they would have an XFS of 10 degrees, meaning that their shoulders and hips now have 10 degrees greater separation.
(If you watch the video below from 1.00 on take a lot at how JT rotates his hips in the downswing. Very impressive and certainly benefiting from XFS)
This is important because of the elastic energy concept discussed in part 2. XFS places a very dynamic stretch on the muscles of the trunk and torso. Muscles can contract more forcefully immediately after being stretched due to the power stored from elastic energy. It is much like stretching an elastic band or loading a bow string. The increase in separation from XFS and the resultant dynamic stretching of the trunk and torso muscles enables a stronger rotation of the body towards the target in the down swing, aiding in club head speed generation.
X-Factor VS X-Factor Stretch:
Dr Phil Cheetham, a well known golf biomechanist published a study in 2000 which examined XF and XFS. The study was very interesting as it analysed X-factor data at the top of the backswing and at the initiation of the downswing. It was hypothesised that highly skilled golfers (handicap scratch or better, many of them were pro’s) would have a greater XF at the top of the backswing and a greater XFS at the initiation of the downswing compared to less skilled players (handicap 15 or greater). The researchers found that there was on average an 11% difference between the highly skilled and less skilled golfers at the top of the golf swing, but that this was statistically insignificant.
Crucially, the skilled golfers increased their X-factor at the initiation of the downswing by 19%, compared to 13% for the less skilled, which was statistically significant (this was accomplished by XFS). The authors suggested that X-factor stretch was more important to an effective golf swing than X-factor at the top of the backswing. A study by Burden et al (1998) backs up the results found by Cheetham (2000). Using 3D analysis the researchers found that in highly skilled players the hips begin the downswing by rotating towards the target, while the shoulders are still rotating away from the target in the backswing. This XFS seems to be an important reason why highly skilled players have higher club head speeds than less skilled players.
On a side note, this X-factor stretch can also be seen in other hitting and throwing sports like tennis, hockey, baseball, javelin, hurling and is in my opinion one of the reasons why athletes with backgrounds in these sports can take to golf so quickly.
How can I improve X-Factor Stretch?
Hip & torso mobility and the motor control to separate the rotation of these segments are the key ingredients to increasing your XFS. Try the the drill below to develop both of these qualities.
Note how the upper body remains still while the pelvis rotates. This ability of separating pelvis rotation and torso rotation is an important ingredient in power generation.
That wraps up the mini series on “Power Essentials”. You now know the basics of ground force, X-Factor, and X-Factor Stretch. More importantly, you also have an exercise to develop each component.
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