Kelvin asked me to post the following - Jeff
Universally Accepted Scientific Terms and Definitions
Let’s start with the simple definitions that everyone should know. You can read Dr. Rob Neal’s paper to get an idea of how biomechanists measure and define the terms.
http://www.golfbiodynamics.com/admin...-2008_rev1.pdf
Here’s part of a paragraph from page 4 detailing the standardized process by which biomechanists define the movements. Pay special attention to the highlighted sentence in bold:
The kinematic variables derived from biomechanical analysis included the peak segmental angular velocities and their times of occurrence as well as the timing lags between these peaks. Angular velocities were calculated and are reported with respect to the local coordinate systems embedded in the segments. In these coordinate systems, the velocities represent the rates of flexion/extension (around the x-axis), tilting/lateral bending or radial-ulna deviation (around the y-axis) and axial rotation (around the z-axis or long axis of the segment).
Flexion and extension of the wrists affect the x-axis and therefore control the loft. Left wrist flexion decreases loft while left wrist extension increases loft.
Obviously, there is more going on than just left wrist flexion vs. left wrist extension but for the sake of simplicity let’s just look at flexion or extension. Left wrist flexion decreases effective loft whereas left wrist extension increases loft.
Radial/Ulnar Deviation
Radial and Ulnar deviation occur in both wrists at the same time.
These movements occur in the y-axis and affect the shaft angle or plane when viewed from the target line. Above Christy is demonstrating ulnar deviation.
Here she is demonstrating radial deviation.
The difficulty with the golf swing is knowing which angle the movement is occurring in. The loss of lag at this point is due to early ulnar devation.
Sergio is increasing radial devation.
At from just prior to impact till impact, Watney shows movement toward ulnar deviation.
Dean Wilson shows the opposite movement toward radial deviation.
Supination/Pronation
Supination and Pronation affect the z-axis or the axial rotation of the shaft. As long as there is rotation in the ulna and radial bone, there is going to be either supination or pronation occurring. From the scientific world, these are the only movements that cause axial rotation of the shaft. Left wrist supination closes the clubface while left wrist pronation opens it.
Here’s Gary Woodland showing left forearm supination. Notice the change in position of the logo of the glove and radial bone of left forearm. He also shows left wrist flexion.
Also, these two pictures of Tapio show a movement of left forearm supination although he calls it only palmar flexion and ulnar deviation, there’s more going on than he thinks. A simple cursory look at the left forearm and you can see rotation of the left ulna. The dots show this rotation or supination.
Qualitative Biomechanical Analysis
Perhaps the most difficult part of qualitative biomechanical analysis for some to grasp is that one must sense the relative changes in position of a joint over time. This takes expert skill and knowledge. Quantitative biomechanical analysis has made this simpler and quantifiable as in Dr. Neal’s article shown at the beginning of this article. They just put a sensor on the left wrist and measure the x, y, z coordinate changes from one frame to the next and can calculate the amount of movement in the three planes of motion. The bottom line is while one can’t quantify movement using qualitative analysis, the data from quantitative analysis can be used to verify the movements.
Relative movements
In trying to understand movements, one must consider not only what position the joint is in at any instant but also how and where it is moving. So let’s take the simplest example and start to unravel this for everyone.
Say we’re looking at a basketball player doing a vertical jump. He flexes or bends his knees before jumping up. So at the very end of his movement to maximum flexion of his knees, he begins to extend his knees to jump. Thus, the athlete is in the process of extending his knees yet, if we didn’t know the movement was occurring, and simply looked at a still photo of his position, one would say his knees are in flexion. However, relative movement shows that he is extending. So which is it? Are we trying to define a position or a relative movement?
For the most part, relative movement or motion analysis is more important to understand than the position at a single instant. Muscles move the limbs and joints and neural input is required to move muscles. Therefore, the brain needs to know how to fire the signals to learn a movement path. Thus the term I have been using all along is “movement toward” extension or, in the case of Hogan’s transition, supination. The muscles used in supination are already firing if the movement is toward supination. This is no different than the basketball player’s quadriceps, glutes and hamstrings all firing to extend the legs and hips to jump from the very outset of the movement. This is the key to understanding and learning.
All or Nothing
This brings up an important point; there are many grey areas when examining wrist and forearm movements. Just as shoulders can accelerate, decelerate and accelerate again, the movements of the wrist are just as dynamic. Just because there’s only a slight movement toward supination that never reaches the end of range of motion does not mean it does not exist. Hogan displays many movements of his left wrist and forearm that change often and rapidly. He may have extended his left wrist at the top of the backswing but flattened it slightly using flexion in transition. Also, since we can see axial rotation of the clubface, it means that supination occurred along with the flexion.
4D system is lacking in some areas
Truth be told, no system is perfect. The 4dswing system is better at measuring the hip/leg and shoulder movements more accurately than others. But the 4D system does not track the 6 DOF (degrees of freedom) movements of the hands.
http://www.amm3d.com/Portals/0/artic...FullReport.pdf
Page 72 shows graphs of the 6 degrees of freedom movements recorded by TPI 3D. If you can read graphs you’ll see that the movements are dynamic and always changing. The AMM3D/TPI3D system measures the x, y, and z coordinates of the left hand/wrist/forearm and can dissect the movements.
Small movements like measuring lateral bend are difficult to measure using the 4D system. Small fast movements of the forearms/wrist/hands are even more difficult to measure without sensors. Could this be the reason for misinterpreting the movements?
The hands/wrist/forearms work together to create a 360 degrees of freedom movement. In the golf swing, it is rare for movements to be only in one plane of movement. Typically they are occurring in two or all three different planes of movement concurrently and this concept seems to elude many people. Thus one must be very careful in trying to do this tedious work or risk making errors.
While thinking you are demonstrating only left wrist flexion, you are axially rotating the shaft. Therefore there is left forearm supination and right forearm pronation.
As Ronald Reagan once said, “Trust but verify.”
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Originally Posted by Jeff Martin
