Swing events are meaningful instants of the swing (Figure 1). Some are readily identifiable but some are subtle so must involve a computed parameter or two for identification of the event. Here are the event names commonly used in the research arena with matching P numbers:
| Abbreviation |
Full Name |
Description / Notable Aspects |
P# |
| BA (TA) |
Breakaway (takeaway) |
This is beginning of the backswing phase. Technically speaking, this is the point when the clubhead deviates from the initial position more than 2 cm. |
P1 |
| Before this event, the ground reaction forces already change to prepare for the backswing. |
| MB |
Mid backswing |
This is when the club shaft becomes parallel to the ground in the face-on view. |
P2 |
| LBA |
Late backswing (arm-based) |
This is when the lead arm becomes parallel to the ground in the face-on view. |
P3 |
| LB |
Late backswing (club-based) |
This is when the club shaft becomes vertical in the face-on view. Depending on the swing style used (e.g. early wrist cocking), this event may appear earlier than LBA in some golfers. |
|
| EPR |
End of pelvis rotation |
This is when the pelvis changes its direction of rotation. Normally, this has to occur reasonably earlier than TB. |
|
| The upper torso (thorax and shoulder line) further separates from the lower torso (pelvis) beyond this event. |
| TB |
Top of backswing |
This is when the club changes its direction of rotation. |
P4 |
| In a dynamic golf swing, the moment arm of the frontal-plane GRF moment becomes max. around this event. |
| EDA |
Early downswing (arm-based) |
This is when the lead arm becomes parallel to the ground in the face-on view. |
P5 |
| This is an imortant event. The frontal-plane GRF moment and pivoting moment become maximum at or before this event. |
| ED |
Early downswing |
This is when the club shaft becomes vertical in the face-on view. |
|
| The angular speeds of the body parts (pelvis, thorax, shoulder line, and the upper lever of the functional-double-pendulum reach their max values about this event or before. If the peak anguar speeds occur after this event, it means the peaks are delayed. |
| MD |
Mid downswing |
This is when the club shaft becomes horizontal (parallel to the ground) in the face-on view. |
P6 |
| This event is used in functional swing plane calculation. The clubhead trajectory between MD and MF is used in the calculation. |
| BI |
Ball impact |
This is when the clubhead impacts on the ball. |
P7 |
| ZC |
Zero cocking |
This is when the upper lever of the functional double-pendulum (the line drawn from the mid-trunk point to the mid-hand point) aligns with the club shaft (lower lever) after impact in the swing plane view. |
|
| MF |
MId follow-through |
This is when the club shaft becomes parallel to the ground. |
P8 |
| This event is used in functional swing plane calculation. The clubhead trajectory between MD and MF is used in the calculation. |
| LF |
Late follow-through |
This is when the club shaft becomes vertical in the face-on view. |
P9 |
ZC (Zero cocking) can be defined in the FSP (functional swing plane) view (Figure 2). The red line shown in Fig. 2 is the upper lever of the functional double-pendulum model: the line drawn from the mid-trunk point (hub) to the mid-hand point (hinge). The lower lever (club) is aligned with the upper lever at ZC.
More events can be added if necessary, such as MGF (Max. GRF).
This division method is obviously based on club's direction of motion before and after the impact.
However, the true beginning of the downswing may not be TB as the body (the pelvis in particular) already rotates in the downswing direction at this point. In biomechanical point of view, it may be more meaningful to use EPR as the beginning of downswing. Also the phase between BI and MF (or BI and ZC) could be considered as a continuation of the downswing motion. So for the analysis purposes, the extended downswing phase (EDS) may be defined as EPR to MF or EPR to ZC (Figure 3).
