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Acceleration Variations (Observations in the Kinematic Sequence)
This is part of a series of new articles on 3D data analysis - lets look at what rates of acceleration tell us about the golfer.

By Greg Rose - Posted December 31, 2007

One key observation you need to make when looking at the Kinematic Sequence is the rates of acceleration for each of the segments (pelvis, thorax, arms, club). Look at the two examples below:


Figure 4.0.1


Figure 4.0.2

Notice on Figure 4.0.1 that all four segments are accelerating relatively at the same rate (slope) from the start of the downswing to when each segment peaks.  Whereas, the player in Figure 4.0.2 has a dramatic reduction in the rate of acceleration of the pelvis (orange arrow).  To understand why this happens, lets review the five major reasons why a segment will have poor acceleration:

Minimal Power - this means that the segment itself is not powerful enough.  Remember, Power = Speed x Strength.  So the segment may need power training to improve.  Initial rate of force development (IRFD) and maximal rate of force development (MRFD) require different training methods (Covered in TPI-CGFI Level 2 Fitness Class).

“An elastic athlete is more efficient because their contractions take less of a conscious thought and are more of a natural reaction. A non-elastic athlete must activate the muscle more to produce force, which requires more energy” - K. Hakkinen

Segmental Weakness - this means that the segment itself is not strong enough to handle the forces that are applied to it while it is trying to accelerate.  For example, in Figure 4.0.2 as the player’s thorax, arms, and club begin to accelerate the pelvis acceleration begins to drop.  This is a classic example of the pelvis not having the strength to stabilize the large forces that are applied from the rest of the body.

Mobility Restrictions - If the mobility is reduced between two segments then the lower segment will not have time to accelerate independently of the above segment since the above segment will be “dragged along” immediately. If the mobility between the segments is good, then the lower segment can accelerate better initially.

Proximal Stability - If the base that the segment is trying to accelerate upon is unstable then the acceleration will be reduced.  This is very much the same as Segmental Weakness, but instability can be due to more than just weakness.  It can be lost due to poor mechanical position, poor balance, muscular endurance limitations, and of course a strength deficit.  A great example of this is beach volleyball.  Ask any player and they will tell you they can jump higher on solid ground since the sand tends to give away under their feet as they try to jump on the beach.

Poor Mechanics - Obviously one of the most common reason for any efficiency breakdown is poor mechanics.  When it comes to poor acceleration, many times a player will get themselves into a position where creating maximal acceleration is not possible.  For example, when a player gets into a reverse spine angle the initial rate of pelvis acceleration is almost always reduced.