Note: Outside the Netherlands one usually speaks about the backstroke but is sometimes also called the backcrawl. However, because of the nature of this website we speak only about the backcrawl. That is because on this website there are more backstrokes descripted.
Because the pull-through of the arms is executed via the body, there is a tendency to swing. Because of this, a good legstroke is essential to compensate the swinging, even more than at the frontcrawl. Besides, the damming function of the legs remains very important.
During the Power-phase the hand follows a semi-circular path from the Catch to the side of the hip. The palm is always facing away from the swimming direction, and the elbow always points downward towards the bottom of the pool. This is done so that both the arms and the elbow can push the maximum amount of water backward in order to push the body forward. At the height of the shoulders the upper and lower arms should have its maximum angle of about 90 degrees. This is called the Mid-Pull of the Power-phase.
The Mid-Pull phase consists of pushing the palm of the hand as far down as possible with the fingers pointing upward. Again, the goal is to push the body forward against the water. At the very end of the Mid-Pull, the palm flaps down for a last push forward down to a depth of 45 cm, creating the Finish of the Power-phase. Besides pushing the body forward this also helps with the rolling back to the other side as part of the body movement. During the Power-phase, the fingers of the hand can be slightly apart, as this will increase the resistance of the hand in the water due to turbulence.
To prepare for the Recovery-phase, the hand is rotated so that the palms point towards the legs and the thumb side points upwards. At the beginning of the recovery phase of the one arm, the other arm begins its Power-phase. The recovering arm is moved in a semi-circle straight over the shoulders to the front. During this recovery, the palm rotates so that the little finger enters the water first and the palms point outward. After a short gliding-phase, the cycle repeats with the preparation for the next Power-phase.
A variant is to move both arms synchronized and not alternating, similar to an upside down butterfly stroke. This is easier to coordinate, and the peak speed during the combined power phase is faster, yet the speed is much slower during the combined recovery. The average speed will usually be less than the average speed of the alternating stroke.
Another variant is the old style way of swimming the backcrawl, where the arm movement formed a complete circle in a windmill type pattern. However, this style is nowadays no longer used for competitive swimming, as a lot of energy is spent on pushing the body up and down instead of forward. Furthermore, the added strain on the shoulder is considered less than ideal and can lead to injuries.
It is also possible to move only one arm at a time, where one arm moves through the Power- and Recovery-phases while the other arm rests. This is slow, but it is used frequently to teach students the movement, as they have to concentrate on only one arm.
The legstroke is also alternating, with one leg sinking down straight to about 30 degree out of the horizontal plane. From this position the leg makes a fast kick upward, slightly bending the knee at the beginning and then stretching it again in horizontal position. However, there are also frequent variants with four or only two kicks per cycle. Usually, sprinters tend to use 6 kicks per cycle, whereas long distance swimmers may use less.
It uses material from Wikipedia article "Backstroke"