The golf swing model is a tool to help answer some questions.
In Chapter 9, we looked at the four options for the hip joint and spinal tilt movements. These options were:
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.
|Basic Rotation||Lateral Movement (miles per hour)||Spinal Tilt (miles per hour)||Club Head Speed at Impact (miles per hour)|
|Duration (seconds)||Total Rotation (degrees)||Distance from Rotation Centre to Ball (inches)||Radius of Circle Followed by the Club (inches)||Basic Rotation Effect (miles per hour)|
|Pure Rotation Without Spinal Tilt||0.41||55.0||100.03||59.52||7.97||0.00||0.00||7.97|
|Push and Clear Without Spinal Tilt||0.41||32.1||100.03||59.52||4.64||0.42||0.00||5.06|
|Pure Rotation With Spinal Tilt||0.41||55.0||63.64||37.86||5.07||0.00||3.29||8.35|
|Push and Clear With Spinal Tilt||0.41||32.1||63.64||37.86||2.96||0.00||4.44||7.40|
Key points to note from the table include:
In comparing the options, here are some further points:
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.
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.
|Club Head Speed at Impact|
|Miles Per Hour||Percent Total|
|Rotation Upper Arm in Shoulder Socket||10.50||13.52|
|Moving Upper Arm in Shoulder Socket||12.78||16.46|
|Moving Shoulder Socket||8.25||10.62|
|Hips - Push and Clear with Spinal Tilt||7.40||9.53|
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.
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.
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.
|Angle Between Lower Arm and Club|
|120 Degrees||130 Degrees||140 Degrees|
|Rotation Upper Arm in Shoulder Socket||11.87||10.50||8.81|
|Moving Upper Arm in Shoulder Socket||12.28||12.78||13.20|
|Moving Shoulder Socket||7.72||8.25||8.67|
|Hips - Push and Clear with Spinal Tilt||6.81||7.40||7.86|
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.
|Default Times||Default Times Reduced by One Frame|
|Time Required (seconds)||Club Speed (mph)||Time Required (seconds)||Club Speed (mph)|
|Rotation Upper Arm in Shoulder Socket||0.15||10.50||0.11||14.00|
|Moving Upper Arm in Shoulder Socket||0.22||12.78||0.19||15.34|
|Moving Shoulder Sockets||0.22||8.25||0.19||9.90|
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:
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.
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:
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.
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.