Applying the Golf Swing Model

Chapter 13: Guide to the Golf Swing

The golf swing model is a tool to help answer some questions.

Hip Joint Movement, the Forward Lean, and the Spinal Tilt

In Chapter 9, we looked at the four options for the hip joint and spinal tilt movements. These options were:

• Pure Rotation without spinal tilt;
• Push and Clear without spinal tilt;
• Pure Rotation with spinal tilt;
• Push and Clear with spinal tilt.

The model tells us that given the default values, Pure Rotation with spinal tilt is the best, followed by Pure Rotation without spinal tilt and Push and Clear with spinal tilt. However, the difference between these options is small, in the order of 1 mile per hour from best to third best.

Key points to note from the table include:

• There is more rotation with Pure Rotation than with Push and Clear. In Push and Clear, the trailing hip joint does not move, and this limits the rotation of the bone structure.
• There is lateral movement inherent in the Push and Clear movement of the hips without spinal tilt. There is no lateral movement in Pure Rotation with or without spinal tilt. There is no lateral movement whatsoever with spinal tilt, because the tilting spine neutralizes the lateral movement from the hips by keeping the shoulder sockets in the same place even though the hip joints move forward.
• The forward lean by itself widens the swing arc, as illustrated by the greater distance from the rotation centre to the ball and the greater radius of the rotation circle. The hip rotation with spinal tilt reduces the swing arc and correspondingly the basic rotation effect, but enhances the spinal tilt effect. On balance, the spinal tilt effect outweighs the basic rotation effect.

In comparing the options, here are some further points:

• Feasibility: Pure Rotation without spinal tilt may not be feasible for most players. The problem is that the back swing rotation from the forward lean shifts the centre of gravity away from the centre of the stance toward the back foot. With weight on the back foot, it may be difficult, if not impossible, for the ankles to generate the rotation needed for the swing.
• Consistency: Swing consistency comes with practice, and any swing can become consistent with sufficient practice. Greater consistency means more hits in the centre of the club and fewer fat or thin shots. Consistency will normally translate in greater average distance. The golfer's eyes are a tool that can be used to increase consistency, because they can be used to inform the swinger whether the body is in its proper place. The eyes can contribute to consistency more easily when the golfer's head is still. This stillness comes through spinal tilting. Without spinal tilting, the forward lean will cause the head to move with hip rotation. The amount of movement will depend on the amount of hip rotation. We have noted that the amount of hip rotation is greater with Pure Rotation than Push and Clear.
• Weight Management/Fat Shots: Pure Rotation without forward lean keeps the centre of gravity in the same place, essentially over the mid-point in the stance, throughout the swing. When we add the forward lean of the upper body without spinal tilting, the centre of gravity changes during the swing. At the start of the swing, the centre of gravity is toward the toes in the centre of the stance. In the back swing, it moves away from the ball and the target. The greater the rotation, the more the movement. In the downswing, the muscle contractions in the ankles and feet need to not only rotate the hip joints/bone structure, but also bring the centre of gravity to the impact position. Even if Pure Rotation without forward lean is feasible, a lot of golfers, particularly beginners, will have trouble with this movement. The result is back foot shots, which are often fat and lack power. Pure Rotation with spinal tilting keeps the weight centred, and eliminates the weight management issue. Push and Clear with or without spinal tilt addresses the weight management question by reducing the amount of back swing rotation, and by generating sufficient power in the push movement to get the weight off the back foot.
• Spinal Health: Spinal tilting can lead to back injuries. One solution is to avoid spinal tilting. If one applies spinal tilting, the amount of tilting can be reduced by using Push and Clear over Pure Rotation.
• Downswing Time: The table above assumes the same downswing time for each of the movements. However, one may be able to execute the Push and Clear movement in less time than Pure Rotation, not only because there is less rotation, but also because the movement involves more powerful muscles. In the golf swing model, a reduction of downswing time in Push and Clear with spinal tilt of 0.046 seconds produces club head speed approximately equal to that of Pure Rotation with spinal tilt.
• The Feeling of Power: Some golfers, particularly men, like the athletic feel of powering into the ball with a powerful movement like the Push and Clear.
• Rhythm: Many golfers tend to jump at the ball with the powerful Push and Clear muscles. For golfers inclined to jump, Pure Rotation may produce a more rhythmic, consistent swing.
• Standard Practice: Most current professional use Push and Clear with spinal tilt.

Try these options and see what works for you.

For most players, the option most likely to be successful is Push and Clear with spinal tilt. This is the option presented in the rest of this document.

Priorities

The table below looks at the individual movements in terms of the club speed as a percent of total club head speed. The numbers are based on the default values. It gives some guidance on how you should be allocating your practice range and exercise time.

Perhaps surprising is the relatively small impact the "hips" have on the total swing. The "hips" are moved by the most powerful muscles in the body, but they have relatively little impact on performance.

To Roll or Not to Roll

Some professionals advise against rolling the forearm and (by implication) rotating the upper lead arm in the shoulder socket. Certainly, not rotating these elements simplifies the golf swing and removes a potential source of error. The ball should go straighter.

However, the forearm roll and rotating the upper arm in the shoulder socket are significant power sources representing, according to the model and its default values, about 27.04 percent of the total swing speed. Most cannot afford to give up these power sources, so the proper execution of these two movements is recommended.

Grip in Fingers or In Palm

In Chapter 3, we noted that if one grips the club in the fingers rather than the palm of the lead hand, the angle between the club and the lower arm is less. We also noted that radial abduction of the wrist also reduces the angle. The smaller angle produces more club speed from the forearm roll and the rotation of the upper arm in the shoulder socket. However, it also reduces the distance from the shoulder sockets to the ball, making other movements less effective. Whether one should strive for a lower angle is a complicated physical question involving a number of aspects of the golf swing.

The table below is based on the club speed calculator and the default values for various angles between the lower arm and the club. It suggests that the smaller the angle between the forearm and the shaft of the club, the greater the club speed. The benefits from the forearm roll and upper arm rotation in the shoulder socket outweigh speed losses in terms of the distance between the shoulder socket of the lead hand and the ball.

Timing

In the golf swing model, the downswing movements did not all start at once. The hips started first, followed by the spinal twist, then the shoulder sockets and upper arms in the shoulder sockets, and finally the rotation of the upper arm in the shoulder socket, the forearm roll, and the wrists.

The model dealt with timing by examining the individual frames in a video of the downswing. There were eleven frames. With the default values, the hips rotated through eleven frames. The spinal twist occurred in the last seven frames. The shoulder sockets and upper arms rotations covered the last 6 frames. The wrists rotated in the last four frames.

Suppose each movement could be delayed by one frame. The table below summarizes the results when the default times for each movement except the hips are reduced by 1 frame. The result is that delaying the various movements by one frame can increase minimum club head speed by 10.79 miles per hour.

The intuitive thought is to hit the ball further by swinging faster and getting all movements to start sooner, whereas club speed and distance can come by delaying the execution of some movements and then performing them faster.

Sergio Garcia's swing illustrates the effect of delaying the execution of movements. He holds his wrists in a cocked position almost until impact, and then uncocks his wrists at the very last fraction of a second, with powerful results.

Swing Setup

Swing setup includes ideas such as bending more or less at the knees, and leaning forward more or less at set up.

Swing setup affects the efficiency of three movements, specifically the rotation of the shoulder sockets around the spine, the spinal twist, and Push and Clear with spinal tilt.

Moving the shoulder sockets and twisting the spine would be most efficient when the line from the ball to the shoulder socket at setup is 90 degrees. As discussed earlier, human anatomy prevents getting to 90 degrees. Measures which can increase the angle toward the optimum of 90 degrees include:

• Leaning forward more. In the golf model, the default value for the forward lean was 30 degrees from the vertical. Note that notable tall players such as Tiger Woods and Adam Scott have a forward lean of around 35 degrees. The shorter Rory Mcillroy has a forward lean of 30 degrees
• Reducing the angle between the line from the shoulder socket to the ball and the ground by:
  1. Teeing the ball higher. A typical modern tee is 2.75 inches long. If 0.75 inches goes into the ground, the ball is 2 inches higher, and the angle falls.
  2. Bending the knees more. This will bring the shoulders closer to the ground and lower the ankles.
  3. Using longer clubs.

Consider bending the knees. The Club Head Speed Calculator includes a parameter reflecting amount of knee bend plus amount of elevation from using a golf tee. The default value for this parameter is 2.5 inches. Here is what happens when the default value is increased.

• 2.5 inches produces a club head speed of 77.64 miles per hour.
• 3.5 inches increases the club head speed to 77.99 miles per hour;
• 4.5 inches increases the club head speed to 78.32 miles per hour; and
• 5.5 inches increases the club head speed to 78.62 miles per hour.

Consider leaning forward more. The Club Head Speed Calculator assumes a forward lean of 30 degrees from the vertical. Here are the club head speed calculations for greater lean:

• 30 degrees - 77.64 miles per hour;
• 35 degrees - 79.28 miles per hour;
• 40 degrees - 80.58 miles per hour; and
• 45 degrees - 81.51 miles per hour.

Note that when one leans forward more, one is also likely to bend the knees more, to keep the balance. Note too that we previously observed that greater knee bend can improve the execution of the Push and Clear movement. The conclusion is that posture issues such as increased forward lean and knee bend can have a noticeable impact on club head speed.

However, increased forward lean and knee bend can affect accuracy. Both will lower shoulder position. Since the distance from the shoulder to the ball is determined by the length of the arm, the length of the club and the angle between the club and the arm, a lower shoulder does not affect its distance from the ball, but it will affect the distance of one's feet from the ball. It will also flatten the swing plane. Regardless of swing plane, there is only one point on the circumference of the circle that will propel the ball forward on the precise target line. With a flatter swing, impact before or after that optimum point will put the ball off line more than with a more upright swing. The diagram illustrates the point.

Driver Length

Should you get a longer driver? The Club Head Speed Calculator's default value is 45.5 inches, which is approximately the average length in mid-2015. Club manufacturers have been moving to longer clubs in recent years.

Increasing the driver length from 45.5 inches to 46.5 inches increases the club speed from 77.64 miles per hour to 79.35 miles per hour. From the golf model, there is a case for a longer driver based on club head speed, provided that you continue to swing the club at the same speed. You also need to take into account hitting accuracy; longer but less accurate drives do not necessarily help your game (but may aid your ego). You also need to take into consideration hitting consistency; what matters is your average driving distance, and averages go up when you hit the ball consistently in the centre of the club.