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Articles
The Difference between X-Factor and X-Factor Stretch
Wed Jan 2, 2013 by Phil Cheetham
From articles that I have recently seen in popular golf magazines it has become apparent to me that there is a misunderstanding of the term “X-Factor Stretch” and that it is confused with the basic X-Factor term. These two terms, in fact, describe two different measurements in the golf swing; which I would now like to explain.
The term X-Factor was coined by John Andrisani of Golf Magazine and made popular by Jim McLean in his article “Widen the Gap” (McClean, 1992). The term was used to describe the difference in the turn angle between the shoulders (upper body) and the hips (pelvis). For example if you turned your shoulders 90 degrees at the top of backswing and your hips were at 50 degrees then your X-Factor would be 40 degrees; i.e. 90 – 50. X-Factor has also been termed “coil” and we at TPI call it “Spine Rotation”. In research carried out by Mike McTeigue et. al. (1994) he concluded that long hitters “generated more of the turn” in the backswing from the X-Factor than the rest of the PGA tour professionals in the group that he studied. So it was concluded that a large X-Factor at the top of backswing was key to hitting the ball far.
In our research (Cheetham et. al., 2001) we looked at another variable in the downswing and I coined the term X-Factor Stretch to describe it. X-Factor Stretch is the increase in the X-Factor at the beginning of the downswing produced by the hips starting down before the shoulders, it is also called “Downswing Loading” at TPI. So if at the top of the backswing the shoulders are turned at 90 degrees and the pelvis at 50 degrees then the X-Factor is 40 degrees, as already explained, but now if the pelvis begins the downswing before the upper body, the X-Factor will get larger (i.e. stretch). For example, if the hips turn in the downswing to 45 degrees before the shoulders change from 90 degrees, then the X-Factor has increased from 40 degrees to 45 degrees. The X-Factor Stretch is 45 – 40 or 5 degrees. So the X-Factor Stretch is the amount of increase in the X-Factor due to the hips starting down before the shoulders.
The X-Factor Stretch is a good thing in the golf swing, in our research we found that the X-Factor Stretch was significantly larger in the high skilled golfers than in the less skilled golfers, but the X-Factor wasn’t. We concluded that the X-Factor Stretch was more important than the X-Factor. In muscle physiology this is known as the “Strech-Shorten Cycle” and from a biomechanical point of view the X-Factor Stretch does several important things that increase the force in the downswing:
· increases the force in the core muscles to a level higher than at the top of backswing,
· elicits the stretch reflex in the core muscles again allowing them to contract stronger,
· increases the amount of stored elastic energy in the muscles.
All these add up to a faster club head speed at impact.
So in summary:
X-Factor is the amount of coil at the top of backswing and is the difference between shoulder turn and hip turn, e.g. 90 degrees of shoulder turn and 50 degrees of hip (pelvis) turn equals a 40 degree X-Factor. TPI Tour average for X-Factor at pelvis transition is about 42 degrees.
X-Factor Stretch is the maximum increase in the X-Factor due to the pelvis starting the downswing before the shoulders. X-Factor Stretch equals maximum X-Factor during downswing minus X-Factor when hips begin the downswing, e.g. 45 - 40 = 5 degrees of stretch. TPI Tour average for X-Factor Stretch is about 5 degrees.
References
Cheetham, P.J., Martin, P.E., Mottram, R.E., and St Laurent, B.F. The importance of stretching the "X-Factor" in the downswing of golf: The "X-Factor Stretch." In P.R. Thomas (Ed.), Optimising performance in golf (pp. 192-199). Brisbane, Australia: Australian Academic Press. ISBN 1 875378 37 5. 2001. Also reprinted by permission in the inaugural issue of Journal of Applied Golf Research (2011).
McLean, J. Widen the gap. Golf Magazine. pp. 49-53. December, 1992.
McTeigue, M., Lamb, S. R., Mottram, R., and Pirozzolo, F. Spine and hip motion analysis during the golf swing. Science and Golf II: Proceedings of the World Scientific Congress of Golf. Edited by A.J. Cochran and M.R. Farrally. E & FN Spon, London. pp. 50-58. 1994.
Phil Cheetham 3/27/2011
"[I]n our research we found that the X-Factor Stretch was significantly larger in the high skilled golfers than in the less skilled golfers, but the X-Factor wasn’t"? I have no problem with the X-Factor Stretch being significantly larger in the high-skilled golfers, but the X-Factor not being larger? How big was your group of analyzed players then? Have a look at the data in the video on https://www.youtube.com/watch?v=CvEzEYl0Re0 (as of 1 min 15 sec): X-Factor average amateur: 40 degrees, X-Factor average Tour player: 74 degrees.... That is a humongous difference! It's not that I think that the X-Factor Stretch is to be neglected, and it could well be that within a group of Tour players with equal X-Factors the X-Factor Stretch makes a significant difference. But I'd think that amateurs should work on increasing their X-Factor mobility first, if that were possible. That may - for them - be more important.
Frank Conijn 11/19/2015 2:20 AM
I've been aware of x-factor stretch for years and this is related to posture as well. However what I'd like to learn more about is the x-factor per say. When Adrisani and then McLean came out with this in the early 90's I never bought into it because the arms aren't responsible for spine rotation and both are key components of a full shoulder turn. It is one thing to say the shoulders turn 50 degrees or more than the hips but too many instructors still teach limited hip turn (lower spine is involved) hence decreasing thoracic spine rotation and limiting the shoulder turn. I've even seen injuries because of the effort to do so. I think it is important as instructors we are taught how the entire spine rotates within the framework of a proper backswing. I'd prefer we focus on quiet feet and knees while allowing one to turn the hips which will offer the resistance required to create an appropriate amount of X-factor.
David Hill 12/14/2014 5:16 PM
I've been aware of x-factor stretch for years and this is related to posture as well. However what I'd like to learn more about is the x-factor per say. When Adrisani and then McLean came out with this in the early 90's I never bought into it because the arms aren't responsible for spine rotation and both are key components of a full shoulder turn. It is one thing to say the shoulders turn 50 degrees or more than the hips but too many instructors still teach limited hip turn (lower spine is involved) hence decreasing thoracic spine rotation and limiting the shoulder turn. I've even seen injuries because of the effort to do so. I think it is important as instructors we are taught how the entire spine rotates within the framework of a proper backswing. I'd prefer we focus on quiet feet and knees while allowing one to turn the hips which will offer the resistance required to create an appropriate amount of X-factor.
David Hill 12/14/2014 5:15 PM
I wish I would have read this article before my session with a client last week. I was explaining coil & x-factor on the backswing for creating power. Then I explained the correct kinematic sequence on the downswing. Nice to know the TPI term that is the transition power move during the the golf swing that trumps the x-factor! Thanks!
Sean Saunders 8/18/2014 4:54 PM
Thank you. Very clarifying.
Anonymous User 7/18/2014 7:55 AM
Thank you Phil for the clarification. Moving on, how can we increase our X-factor stretch? Thank you, Antonio
Antonio Ferrer 7/9/2013 6:02 PM
Hi Antonio, there are a variety of drills available but as a long-time instructor the ability to load early into the rear hip (ala Hogan) while the arms have still only reached the 3/4 position in the backswing is key. Keep in mind even though the lower spine has finished rotating the thoracic spine can still turn more. While this is happening the lower body (left knee and then pelvis) initiate the downswing increasing the X-factor stretch. What is not mentioned in this article is the abililty to load deep into the rear hip (glute strength and internal hip flexibility can help). This is important as well for distance because as the arms finish the backswing travelling upward, the posture is remaining down creating extra elasticity (like a bow and arrow). If your lats are flexible then look out...you'll bomb it.
David Hill 12/14/2014 5:27 PM