In golf, “flex” is defined as “the relative strength (stiffness or softness) of a club shaft,” according to PGA pro Mark Blakemore. He notes that a shaft’s flex point, also known as the kick point, is the spot where the shaft will bend the most. Both the degree of flex a shaft contains and the location of its flex point will affect the distance a player is likely to achieve with that club.
Types of Flex
Golf shafts are typically grouped into five flexibility categories.
The most flexible shafts are labeled “L,” for ladies. The progressively stiffer categories are A (senior); R (regular); S (stiff); and X (extra stiff). Unfortunately, as “Golf Magazine” editor Scott Kramer notes, there is no industry standard regarding flex. In other words, two S shafts manufactured by two different companies may have different amounts of flex.
Potential Energy
A golf shaft stores energy when it flexes during the backswing and the start of the downswing. The energy is released at impact when the shaft whips forward. As the Leaderboard website notes, if you put the grip end of a club into a vise, then pull back on the clubhead, you’ll feel tension in the club. This tension is the stored energy, which will spring the club head forward if you release the club. To achieve maximum distance, Leaderboard.com explains, the stored energy must be released at the moment of impact during a golf swing. If the energy isn’t released quickly enough -- in other words, if the shaft is still flexed on impact -- you’ve wasted potential energy. If the shaft straightens prior to impact, the potential energy you have built is gone and, again, you’ll lose distance on your shot.
Which Flex to Use
In general, Kramer explains, a golfer with a high swing speed should use stiffer shafted clubs, while those with lower swing speeds require more flexible shafts. That’s why PGA Tour players, who typically have high swing speeds, tend to use stiff or extra stiff shafts. Kramer recommends having a professional club fitter measure your swing speed to help determine which type of shaft you should use. Longtime USGA technical director Frank Thomas advises golfers with swing speeds of 80 to 95 mph to start off with a regular flex shaft, then make any necessary adjustments.
Flex Point
Golf club manufacturers can adjust the shaft’s flex point, primarily to produce a higher or lower ball flight. All else being equal, Thomas explains, a higher flex point produces lower ball flight, while a lower flex point results in a higher launch angle.