X-FACTOR AND X-FACTOR STRETCH IN THE GOLF SWING

Anecdotally, many golf coaches emphasise the importance of developing a large separation or differential between the ‘hips’ and ‘shoulders’. This angle differential between the pelvis and trunk is formed by two virtual lines through the pelvis and trunk (see diagram below). Maximising pelvis and trunk differential during the backswing, has been associated with longer driving distances. McLean (1992) was the first to describe this event termed ‘X-Factor’, after analysing a small group of tour professionals. Using a correlation analysis, McLean (1992) found a positive relationship between X-Factor and golf driving distance.

In contrast to the findings of McLean, McTeigue et al. (1994) failed to demonstrate a greater pelvic-trunk differential in professional golfers compared to a group of amateurs. McTeigue et al. (1994) found no difference in X-Factor, between tour professionals (32°), senior tour professionals (29°) and amateurs (34°). Given these conflicting findings, Cheetham and colleagues (2001) went on to investigate the relationship between X-Factor, as well as the increase in X-Factor early in the downswing, which they termed ‘X-Factor Stretch’. It was hypothesised that skilled players would increase their X-Factor early in the downswing, due to the pelvis rotating towards the target before the trunk; this is often referred to as 'leading with the hips' by golf professionals. Results indicated that skilled golfers (handicap less than zero) increased their X-Factor Stretch significantly more than a group of novice golfers (handicap greater than 15) early in the downswing (skilled = 19% and novice = 13%). Furthermore, there were no differences in X-Factor between the skilled and novice groups. It was concluded that X-Factor Stretch, was more important to an optimal swing than simply the difference between trunk and pelvic rotation at the top of the backswing.

Figure 1. The above graph demonstrates an elite male golfer during the backswing and downswing phase of the golf swing. At address the golfer is in an 'open' position with his trunk being rotated 11° toward the target. Once the backswing starts the trunk rotates away from the target, closing this difference created at address. During the backswing the trunk rotates much more than the pelvis, leading to a large pelvis-trunk differential (i.e. X-Factor). The shaded blue section represents the transition at the top of the backswing. During the transition and start of the downswing, the hips commence rotating back toward the target causing a relative increase in the pelvis-trunk differential (i.e. X-Factor Stretch). The above male golfer has a maximum X-Factor = 62° and an X-Factor Stretch = 8°.

X-Factor and X-Factor Stretch, which are developed during the backswing and early part of the downswing, are thought to cause rapid stretching of the pelvis, trunk and upper arm muscles prior to shortening of these same muscles (Cheetham et al., 2001; Hume et al., 2005). This eccentric-concentric pattern of muscle activation, whereby a muscle undergoes lengthening prior to rapid shortening is referred to as a stretch-shorten cycle (Enoka, 1994). Although the exact mechanisms of the stretch-shorten cycle remain contentious, several explanations put forward include: (i) an increase in time available during the eccentric phase allows a muscle to build up a high level of activation before shortening (ii) the storage and utilisation of elastic energy through the series elastic elements (iii) triggering of spinal reflexes which lead to greater muscle stimulation and (iv) a change in contractile mechanics (i.e. cross-bridges) allowing for a more forceful muscle contraction (Ingen Schenau et al., 1997; Walshe et al., 1998).

The golf swing is thought to involve a stretch-shorten cycle, particularly during the transition between backswing and downswing (Cheetham et al., 2001; Neal et al., 2001; Hume et al., 2005). The benefits of improved performance associated with a stretch-shorten cycle in the golf swing have been attributed to two of the aforementioned mechanisms: the stretch reflex and the storage and release of elastic energy by the muscles of the trunk and pelvis (Cheetham et al., 2001). The length properties of individual muscles, or muscle groups, however have not been directly examined during the golf swing.

In summary, the available evidence suggests that the greater the pelvis-trunk differential, the further the individual is likely to hit the golf ball.

GENDER RELATED DIFFERENCES IN GOLF INJURIES

Although the number of epidemiology studies investigating injury characteristics of golfers continues to increase, methodological approaches remain variable. Several studies have employed retrospective, self-reported injury history questionnaires, many of which do not differentiate between injuries caused by occupational accidents, activities of daily living, or golf specifically. Response rates have also been typically low, which may have resulted in selection bias (McCarroll and Gioe, 1982; Sugaya et al, 1999).

The studies that have investigated injuries amongst golfers, have failed to find gender differences in injury frequency even across differing skill levels (McCarroll et al, 1990; Batt, 1992; Gosheger et al, 2003). A consistent pattern seems to emerge, however when site or location of injury is examined. Amongst females, there is an observable trend toward increased incidences of upper limb injuries i.e. wrist, elbow, shoulder, whereas in males low back injuries predominate (McCarroll and Gioe, 1982; McCarroll et al, 1990; Batt, 1992; Theriault et al, 1996; McHardy et al, 2006).

Some authors have attempted to explain this trend, by suggesting males may have higher swing velocities and more powerful trunk rotation during the downswing. Differences in physical characteristics such as strength, flexibility, and anthropometrics are also thought to contribute to the observed gender differences in injury location (Theriault and Lachance, 1998). Currently, there is still a distinct lack of published kinematic data to support these suggestions. This lack of gender specific kinematic data is even more apparent in females, where to date only one study has specifically analysed the kinematics of the female golf swing.

So what does the mean in practical terms for the everyday golfer? Well for females, they probably need to work on strengthening their upper limbs and in particular the muscles that control and stabilise the scapulae; such as the rhomboids, lower trapezius, serratus anterior and rotator cuff muscles. Strengthening muscles around the trunk and back ('core') is also likely to assist females from an injury prevention perspective. Males on the other hand probably need to work on flexibility of their thoracic spine, lumbar spine, and hip joints while also working on strength, endurance and stability of their 'core' muscles, including the deep abdominals, low back muscles, gluteal muscles and pelvic floor muscles.

BACK INTO THE SWING - PREVENTING LOW BACK PAIN?

Low Back Pain is a common and costly problem for professional and amateur golfers.  It often costs both groups time away from golf, and for the professionals, low back pain will potentially impact upon their livelihood.  It is the most common injury in male professionals and the second most common injury in female professionals.  In the amateur golfer the stats are similar. Injury rates have been reported to be as high as 40% in some studies.

Low back pain can also be very disabling to the golfer. Some golfers have reported being forced out of the game for 12 months or more.  These alarming statistics have resulted  in Low Back Pain receiving far more attention then ever before, but we are still only just beginning to understand the complex nature of the problem.  The exact cause is still undetermined, but numerous suggestions have been put forward. These include:

In recent times most attention has been focused on improving and maximising the physical conditioning of the golfer.  The majority of professionals have taken note of this, and now many employ their own physiotherapists and fitness instructors.  The result is fitter, stronger and better performing athletes.

The most difficult point for the everyday golfer, is knowing what exercises to do.  Exercises need to be individualised to the golfer’s body type, swing mechanics and likes and dislikes.

The muscles of the trunk are one area that forms an important part of a golfers exercise program.  Recent research has found that poor trunk muscle endurance was a good predictor of low back pain in golfers. Therefore, trunk muscle exercises should form an important part of a golfers program.

Side Bridge                                                                   PLANK

A number of simple exercises the golfer can do to improve their trunk endurance can be seen above. It is important though that the golfer unaccustomed to physical exercise, consult a qualified health professional before commencing an exercise program. See disclaimer.

ELBOW PAIN - TENNIS ELBOW OR GOLFER'S ELBOW?

Pain around the elbow is a frequent complaint amongst golfers. Two of the most common causes of elbow pain are ‘tennis elbow’ and ‘golfer’s elbow’. Interestingly, tennis elbow occurs 6 times more frequently than golfer’s elbow and usually affects the lead arm. Furthermore, both of these conditions can significantly affect a golfers’ ability to play and practice, with some golfers unable to pick up a club for 6 months or more.

Despite the fact that these conditions occur frequently, both are still poorly understood and often poorly managed. This article outlines the pathological process behind both tennis elbow and golfer’s elbow and also some of the common causes of tennis elbow. There will be a particular emphasis on tennis elbow due to its predominance amongst golfers.

Figures 1a & 1b. Courtesy of Multimedia Group 2000

Golfers with tennis elbow will experience symptoms around the outside part of the elbow, whereas those with golfer’s elbow will have symptoms around the inside of the upper part of the forearm or elbow. The most common symptoms are pain and weakness when gripping an object such as your club. The anatomical structures at fault are the common extensor tendon in tennis elbow and the common flexor tendon in golfer’s elbow (Figures 1a & b). The extensor muscles bend the wrist backwards (extension) while the flexor muscles bend the wrist downwards (flexion).

The pain associated with tennis elbow is a result of the pathological breakdown of the common extensor tendon. Essentially, there is a disruption of the collagen fibres that make up the tendon. This occurs where the extensor tendon attaches on the lateral, or outside part, of the elbow.

During the golf swing the wrist extensor muscles maintain the lead wrist in a slightly extended position during the downswing and through impact (Figure 3b). In order to maintain this position, the wrist extensor muscles contract with a significant amount of force. It is these large forces which contribute to the breakdown of the extensor tendon at its origin.

A number of factors have been proposed to cause tennis elbow in golfers, including:

Overuse ie. practicing too much without sufficient rest or recovery periods

Other non-golfing related causes such as heavy pruning in the garden

This list is by no means exhaustive, but should be kept in mind if you suspect you are developing the early signs of tennis elbow. As initial symptoms are often mild, golfers will often try to continue to play through them, only perpetuating the problem. It cannot be overstated how vital it is to manage the problem appropriately as soon as symptoms are experienced. Progression to a chronic condition will result in significant time away from golf.

If you do experience symptoms of what you think is acute ‘tennis elbow’ (i.e. symptoms <6 weeks), try to rest for a few days and trial ice over the area. You should also consider whether any of the above causes may be contributing to your problem and attempt to address them. If there is no change within a week, it is advisable to seek help from a qualified health professional with a good understanding of the golf swing.