Maximizing golf drive distance
With over 26.5 million golfers just in the United States, there is an increasing demand for products, coaches and research to help maximize driving distance off the tee. After the introduction of the larger heads on woods, changing the shaft material and different composition of metals being used in the club heads themselves, research has now changed to examine the biomechanics of the golf swing in order to help understand and maximize the golf shot. This article is a summary of a research review by Hume et al (2005).
Biomechanics simply means taking the principles of mechanics and applying them to a moving system – in our case the golf swing. Golf biomechanics breaks down the swing and uses computer models to compare differences between novice and expert golfers, as well as looking at speed and timing of movements. The golf swing has been broken down into four main phases: I) Set-up II) Backswing III) Downswing and IV) Follow through. This article will examine each phase and discuss research relevant to each section that is designed to increase the efficiency of your swing and thereby help maximize distance from your shot. All of the following descriptions will be with reference to a right-handed golfer’s set-up and swing.
SET-UP
In addition to being having a proper stance that is aligned with the target, the grip, body position and bodyweight distribution will be addressed in this section.
Grip
There are three types of grip you can have on your club - strong, neutral and weak. For the right-handed golfer looking down at their hands, a strong grip is where the hands are rotated clockwise on the club so that more of the back of the left hand is exposed. A strong grip allows for more power to be released during downswing but it also results in less accuracy and more ‘missed’ shots. In contrast, a weak grip is where the hands are rotated counter-clockwise revealing more of the back of the right hand. This grip decreases the amount of hand contribution to club-head speed but increases the club-face control. A neutral grip is simply between the two, both in set-up and in club-head speed and control. The amount of mobility in your wrists also influences the type of grip that is optimal you for. A stiffer wrist (10° radial deviation) is more suitable to the strong grip whereas a more ‘normal’ or flexible wrist may be more comfortable with a neutral grip.
Stance
At set-up, the knees should be bent 20-25°, waist bent about 45° at the hips, and a right shoulder tilt of about 16° due to the right hand being lower on the club and protraction (forward displacement) of the shoulder blade.
BACKSWING
The first 40-60cm of the backswing is done in what’s called a ‘one-piece takeaway’ where the position of both arms and chest remains the same. The club-head moves back in a line almost perpendicular to a line through the ball and your toes. After this time, the hips continue to rotate and once the hands reach hip level, the right elbow starts to bend as the spine continues to rotate and elevate the club. At the top of the backswing, the wrists are cocked radially (downwards). The final position of the backswing has the left hip externally rotated with the left foot pronated and tibia internally rotated. The right hip is internally rotated and the right leg bears approximately 60% of your bodyweight.
Differences in these optimal positions can be a result of tight muscles and joint range of motion. For example, a decrease in right hip internal rotation can cause the hip to rotate up and back, resulting in a straightening of the right knee. Something else to look for in the backswing is if the left heel lifts off the ground. This may indicate a tightness in left hip external, and/or tibial internal rotation. Finally, flexibility of the spine is one of the main determining factors for the range of your backswing. Computer analysis has determined that the longer the backswing, the greater the club-head velocity at impact.
DOWNSWING
The downswing is often further subdivided into two phases, I) the forward swing phase, and II) the acceleration phase. The downswing is where you get to add power behind your stroke and this is where the proper set-up and backswing pay off. During downswing, the left hand and arm dictate the path the club will take while the right arm provides power mainly in the acceleration phase of the swing. The plane of the downswing is a little more vertical then the backswing in order to maximize speed and accuracy of ball contact.
The first motion in the forward swing phase is initiated by the left adductor magnus and the right gluteus maximus, medius and minimus. Those muscles work together to stop the right pelvic rotation used in the backswing and start the left pelvic rotation necessary during the downswing. The erector spinae and abdominal obliques also fire to help accelerate the torso and rotate the spine during the acceleration phase.
The most important factor in influencing contact velocity is in fact timing and magnitude of wrist un-cocking. It has been found that over 60% of the variance in club head velocity is due to the degree of wrist-cocking (Robinson et al, 1994). Wrist-cocking was also able to generate an additional 9% increase in club-head velocity at contact (Sprigins et al. 2000). It is suggested that the optimal time during the downswing to perform the wrist-cocking action is once your lead arm is 30° below the horizontal.
Changes in stance at time of ball contact are as follows: shoulder and hip rotation are 27° and 43° to the left respectively while 80% of your bodyweight has been transferred to the left leg.
FOLLOW-THROUGH
Biomechanically speaking, the purpose of the follow-through is to slow down the rotational forces developed during the downswing phase. This action is achieved through eccentric muscle contraction in the legs, hips, trunk and arms. The shoulders, waist and trunk continue to rotate to the left while slowing down both the velocity of the club as well as intrinsic rotational velocity of your body. Once the hands reach shoulder level, the elbows bend in a final effort to slow club head speed.
The X-Factor
What is the X-Factor and why is it important?
The X-factor is the difference between hip and shoulder rotation at the top of your backswing. McLean (1992, 1993) found this to be more important in maximizing drive distance than your total shoulder rotation. It was originally thought that longer driving professional golfers had a larger X-factor than short drivers. This did not hold up and explain all the cases between long-driving golfers and shorter drivers so further investigation was done to explain the role of the X-factor. It was then discovered by Cheetham et al (2000) to be more complicated than just the difference between the hip and shoulder rotation angles at the top of the backswing. They discovered that the maximum X-factor during the downswing (called X-factor stretch) was determined to be more important in optimizing drive distance. Therefore, it was concluded that the maximum X-factor during backswing may increase X-factor stretch developed during the downswing, and it is the magnitude of the X-factor stretch (usually developed during the beginning of the forward phase) that is the primary difference between amateur and professional golfers. Other factors that differentiated amateur and professional golfers were the ground reaction forces (GRF) developed during the swing. It was found that professional golfers had greater GRF and these forces were developed over a shorter time period. GRF are developed by using your feet to push into the ground in an attempt to generate momentum that can be transferred to the club and ball. To simplify this even further, one can think of a professional golfer who generates more force in less time then the amateur golfer and this can be said to be a more explosive movement. Therefore, the more explosive your swing, the more force you will impart on the ball and the further it should fly.
Role of Strength and Flexibility
There have been a number of studies looking at the role of strength training and flexibility training of golf drive distance. However, due to poor experimental design, few conclusions can be drawn from the results of these studies. There is some computer simulation data that would suggest that the greater the range of motion during the backswing, the greater time there is to develop force during the downswing which optimally should result in further drive distances.
References:
- Hume PA, Keogh J, Reid D. The role of biomechanics in maximising distance and accuracy of golf shots. Sports Medicine. 2005: 35 (5): 429-449
