This stroke analysis includes a moving sequence in real time, and a moving sequence where each frame is displayed for .5 of a second. There is a collage of still frames at the end of this analysis.

The following image sequence is in real time. It will play through 10 times and then stop. To repeat the sequence, click the browser's "refresh" or "reload" button.

dc201001

The following image sequence shows each frame for half a second. It will play through 10 times and then stop. To repeat the sequence, click the browser's "refresh" or "reload" button.

dc201005

Notable Features

This sequence is presented because its aspect allows one to see some of the most common errors made in backstroke swimming.

  • Dyana Calub's arm strokes enter too far behind her head. This causes her hips to sway to the side upon which the entry is made. Thus, on entry, her hips move beyond streamline to that side. This gives a curved alignment to her body, which causes an increase in frontal (form) drag resistance.
  • That position sets up initial stroking forces that are lateral, rather than backward. The laterality causes her hips to move to the opposite side of the pulling arm. Consequently, as she moves down the pool, her hips and feet (in opposition to the hips) move from side to side (a "snaking" movement). This moves large amounts of water, the energy for that movement coming from the swimmer. Consequently, a substantial amount of the swimmer's energy is squandered moving water side-to-side rather than being applied to propulsion. The movement of the water in this fashion is one form of wave resistance.
  • Both arms are extended too much in the middle of the pulling phase. Greater flexion at the elbow would have produced more direct and powerful pulling actions. The wide sweep also contributes to counter-balancing hip and leg sway.

What results from these inefficiencies is a large amount of drag resistance. An exaggerated amount of energy is required to overcome the increased resistance. Both resistance and energy requirements increase with swimming velocity. There comes a stage where resistance is of such a magnitude that the swimmer cannot generate any more force, or harness any more energy, to swim faster. When that stage is reached, the swimmer performs at terminal velocity and the only way of improving performance is to decrease resistance and/or improve the mechanics of propulsion. In the case of Dyana Calub, some options for improvement are

  1. Enter with the hand/arm behind the shoulder, rather than the head. This would reduce hip and leg sway.
  2. Flex the elbow and medially rotate the upper arm immediately upon contacting the water. This is the same action as developing an elbow-up position in crawl stroke. This will reduce lateral movements and direct propulsion backward earlier in the movement pattern.
  3. Flex the elbow at least 90 degrees in the middle of the pull. The propulsive force will be closer to the mid-line of the body, reducing the amount of rotation (sway). The propulsive force will also be stronger as adduction and elbow flexion will produce a more direct force application. The increased elbow flexion also makes the arm position stronger and more resistant to fatigue.

The above actions should reduce sway, and therefore, reduce resistance. The stronger, more direct force application should increase propulsive forces and efficiency. These factors should make it possible for Dyana Calub to improve her performances considerably.

dc20100