Total Performance Golf
Kinematic Sequence
Comparison of 2 Kinematic Sequences
In this article two swings will be compared using data from the Titleist Performance Institute.
By Phil Cheetham - Posted February 14, 2006
In this article two swings will be compared using data from the Titleist Performance Institute (TPI) in Oceanside California. One is from an elite golfer and one is from a lesser skilled golfer. The methods used by TPI are based on a full-body 12-sensor analysis using the AIM-3D golf swing biomechanics system (Advanced Motion Measurement LLC) and the Liberty electromagnetic tracking hardware (Polhemus Inc). The sample rate is 240 samples per second.
Skilled Golfer
Less Skilled Golfer
The graph labeled “Skilled Golfer” is the kinematic sequence of one of the best golfers in the world. The graph marked “Less Skilled Golfer” is that of an amateur golfer. The area of interest in the graph is between the top of back swing and impact, the “T” line and the “I” line, near the middle of the graph. The red line is the pelvis rotation speed, the green is the thorax (trunk), the blue is the arms (as a group) and the brown is the club.
During the downswing all body segments must accelerate and decelerate in the correct sequence with specific timing before impact. The correct sequence for the major segments is: the pelvis, thorax, arms and then trunk. The motion must occur sequentially with each peak speed being higher and later than the last one. This is necessary to efficiently transfer energy and accelerate each body segment. In addition to transferring energy across each joint, energy can be added by the muscles of each joint. In fact if the timing is wrong energy can be dissipated instead of added and as a result speed will be lost. Also the over use of a specific body segment to overcome the deficiency of another may result in injury.
It is obvious looking at the skilled golfer’s curves that there is a definite kinematic sequence; the red curve (pelvis rotation speed) accelerates slowly then decelerates slowly, the green curve (thorax rotation speed) does the same but faster, similarly with the blue curve (arms rotation speed) and finally the brown curve (club rotation speed) which is sharpest and fastest. Each peak is shifted to the right slightly from the previous one showing the correct segmental sequencing order of pelvis, thorax, arms, club. All of the body segments peak and then decelerate before impact, with the club speed peaking at impact. Notice also that each curve has a “double hump” in this region and that the second hump is after impact and of a smaller magnitude (not as fast) as the previous hump. This is due to the club pulling on the golfer during follow through and club deceleration.
The less skilled golfer shows no such sequence with the peaks of each curve being totally out of order. Admittedly, the arms and club show a similar pattern to the skilled golfer but the pelvis and thorax do not. The pelvis rotation speed peaks at impact and the arms curve “attempts” to have a hump in the forward swing but in fact continues increasing to a higher speed in the follow through phase. This golfer has a faster rotation speed of the thorax in the follow through than in the downswing! This suggests that the body segments contribute little, and the arms and club produce most of the effort.
Kinematic Sequence Data Table
Now lets look at the kinematic sequence data for specific values derived from the kinematic sequence graphs. These tables are for the same two golfers and swings. For a complete definition of each of the terms in the table please see the article: “Key Parameters of the Kinematic Sequence” also in this wed site section.
Skilled Golfer
Less Skilled Golfer
Looking at the tables above we see that the skilled golfer’s acceleration values are, in each case, larger that the less skilled golfer’s, especially the pelvis and trunk (thorax). The less skilled golfer has no decelerations of the pelvis and trunk before impact and relatively small decelerations of the arms and club. Maximum segmental speeds are all lower for the less skilled golfer than the skilled golfer, as is each of the speed gains.
The skilled golfer however does not have the expected transition order changing from the backswing to the downswing with the club first, then trunk, then pelvis and finally arms, however, the expected sequencing of the peaks before impact is shown. The less skilled golfer shows none of the expected sequencing in either transition or pre-impact.
From reviewing the example data it can be seen how illuminating the kinematic sequence curves are and how important these and the key parameters can be in analyzing a golfer’s swing. There are drills and exercises that have been designed to fix these typical problems shown by the kinematic sequence curves. This method of biomechanical analysis improves the ability of the coaches and trainers in designing effective training programs for the athletes.