— ADVERTISEMENT — DIGITIZING THE SWIMMING STROKE: FREESTYLE


By Genadijus Sokolovas, Ph.D. Global Sport Technology, Inc. www.globsport.org


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lobal Sport Technology offers Swim power tests and other services such as lactate tests, training design and e-coach software to USA Triathlon members. Twenty-


eight olympic champions and more than 45 medalists have utilized the Swim power test.


The new Swim power test records swimming velocity and


force instantaneously at 60 times per second. The changes of swim velocity are individual, and digitizing technique provides an opportunity to detect weaknesses in swim stroke such as differences between left/right arms, breathing to the left/right sides or sighting technique. Based on individual strengths and weaknesses, specific drills and training may be developed to improve the swimming technique.


Changes of Swimming Velocity freestyle swimming cycle (figure 1) includes two main phases:


left arm phase (A-D) and right arm phase (D-A). Both phases have been digitized by breaking them down into three smaller phases: • entry phase – A to B for left arm and D to e for right arm • pull phase – B to C for left arm and e to f for right arm • exit phase – C to D for left arm and f to A for right arm


To digitize the freestyle swimming cycle, we are using six


changes of the swimming velocity: A – Left arm entry swimming velocity (figure 2) B – Drop of the swimming velocity of the left arm C – peak swimming velocity of the left arm D – right arm entry swimming velocity e – Drop of the swimming velocity of the right arm f – peak swimming velocity of the right arm


Figure 2. Left arm entry swimming velocity (A) (the vertical green line in the middle indicates swimmer’s position on the video).


Digitizing the Freestyle for Elite-Level Swimmers Left and right arm strokes will differ for individual athletes.


Breathing may reduce velocity, and a drop in swim velocity dur- ing the breathing is smaller for swimmers with better technique. freestylers reach the highest velocity towards the end of the stroke. Depending on the individual technique, swimmers may lose some velocity in the middle of stroke (B point in the left arm stroke and e point in the right arm stroke). In many cases, the loss of swimming velocity is related to the outsweep/insweep motion in the middle of the stroke. Male swimmers have a tendency to increase velocity from


point D (beginning of the right arm stroke) to point e (drop of velocity in the middle of the right arm stroke). female swimmers tend to drop more velocity in the middle of stroke on both arms. Less powerful swimmers are doing larger outsweep/insweep motion in the middle of stroke. The consequence of this motion is a larger loss of velocity. Women tend to have a larger drop of velocity in the middle of their stroke due to their strength. Difference in velocity between arms may reach more than 5


percent for some swimmers. Such a big difference may require specific work (drills, strength) to improve technique. To minimize the difference between left and right arm stroke, athletes should swim using one paddle on the weaker hand. Although there are individual variations, men tend to have


slightly shorter e-f phase, when the right arm moves from the drop of the velocity in the middle of stroke to the peak of the velocity at the end of stroke. It indicates that men reach a peak of swimming velocity of the right arm (f) earlier in the stroke than women. As result of that, the next phase (f-A) is longer for men in comparison with women. Most elite-level women have slightly longer duration of right


arm stroke. for some individuals, the difference between the duration of left and right arm stroke may reach up to 14 percent — a pretty sizeable difference between arms. An athlete with a large difference between arm strokes should work on swim technique to minimize it to swim more balanced in the water. Swim power tests reveal individual strengths and weaknesses


Figure 1. Freestyle velocity curve for an elite level swimmer.


that are useful to develop individual training to improve swim- ming technique. To schedule tests with us and improve the swim skills of your athletes, please email us at info@globsport.org or call 719-321-6975.


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