The moment of the “pull finish” in the Snatch?
The final moments of the pull in the Snatch are brief, so brief that it is exceptionally difficult for both the athlete and the coach to interpret what actually happens. If the pull, for example, has a duration of 900 milliseconds (0.9 seconds) from the moment the pull begins to the moment the athlete reaches “full extension” of the body, then the final stages of the pull which occur as the bar passes the mid-point of the thigh might only last 100-150 milliseconds. This extremely short time duration is virtually the blink of an eye, and makes evaluation of the athlete’s actual movement very difficult with the naked eye.
Video technology, hardware and software, greatly assists in analysing and understanding what happens in such short time intervals. Software such as Coach’s Eye is a marvellous aid to the coach. The ease with which the video can be played at slow speed forwards and backwards with finger control enables the coach to study the action to a very high degree. But the action in the final stages of the pull happens so fast, that even normal video at 30 frames per second (FPS) does not provide enough clarity. The time interval between frames at 30 FPS is 33 milliseconds (0.033 sec) and although this might seem sufficient, critical detail can be lost between frames. In may well be that the instant the athlete reaches full extension falls between two frames. Furthermore, at 30FPS, the picture is likely to be somewhat blurred when the athlete is moving fast at the finish of the pull. It is well to note that at this stage of the snatch, the bar will increase in height 6 cm between frames.
A camera that can capture video at 100 FPS will provide far greater detail and likely there will be no blur. It becomes possible to see very precisely how well the athlete achieves full extension and even measure the amount of vertical displacement of the bar. At 100FPS, the time interval between frames is just 10msec (0.01 sec) and even in this very short time the bar will move 2 cm. Importantly. the clarity of individual frames allows better analysis of elements of technique such as body extension, foot take-off and landing, closeness of the bar to the body and the moment of the lockout.
The following illustration is drawn from video frame judged to be the moment of maximum extension of the body for the athlete in the Snatch pull. A Sony Cybershot RX10 Mark 2 was used to take the video.
After this frame, the athlete’s height decreases. Is this the “finish of the pull”?
In the following illustration, the position of maximum extension (shown above) is on the left and the position on the right is 50 milliseconds (0.05 second) later. The athlete’s height is now approximately 1 centimetre less but the feet have not yet left the ground or moved.
One can speculate that this ability to keep feet on the ground longer (even by only 50 milliseconds) will enable the athlete to exert greater impulse on the barbell. Even though upward force on the bar may be relatively little at this point, it will contribute to the height of the pull.
The ability to keep feet on the ground and continue to exert upward force on the bar for a few moments longer in the finish of the pull is an advanced element of skill. Perhaps this ability is what coaches mean when they use the coaching cue “finish the pull!”.
It is easy to assume that the detail provided by videography using smart phones is sufficient for technique analysis. Indeed, it may be for much of the lift. However, in the final moments of the pull, the athlete’s movement is exceptionally fast and important detail can be missed. On the other hand, the clarity provided by camera’s such as the Sony Cybershot is astounding at 100 frames per second. Compiling photo sequences from extracted video frames provides the coach with a much higher level of clarity that makes technique analysis far easier.
The illustrations are taken from a video of Kiana Elliott in Hobart, Tasmania at the 2017 Australian Championships. Kiana Elliot was Bronze Medallist in the 2016 IWF World Junior Championships.
