The back

Some teachers propose the back as the first style due to its alleged respiratory advantages, however this technique has disadvantages related to the biomechanical levers that act in disadvantageous conditions.
The ideal backstroke swimming position is more inclined than the one you tend to take in freestyle.
The head, slightly bent forward, causes a sinking of the pelvis, allowing the lower limbs to be at the right depth, which is essential for the legs to be able to develop their own action in the best possible way.
The biomechanics of the lower limbs in the back are similar to that of the crawl.
The action of the leg kick also develops on a diagonal plane in order to counterbalance the skidding created by the underwater phase of the stroke.
During the pushing phase, the elbow must be higher than the hand, which pushes down past the thigh.
When the students already have a certain mastery of the back, it is good to teach them the roll of the shoulders, that is the rotational movement of the shoulders, which is certainly more hydrodynamic and powerful.
Turn: at a certain distance from the wall, the swimmer begins to rotate on the side by means of a combined action of pulling and pushing the arms, until the same swimmer leans on his chest, and then begins the actual action of the tack.
In turns, the competitor may touch the wall with any part of the body.

Data sheet

Movement

Alternating and cyclical for both the upper and lower limbs

Body position

Supine; frontal resistance must be minimized by allowing the legs to descend to an adequate depth and preventing water from passing over the forehead and eyes.

Upper limb movement

1) recovery action 2) underwater action

1) Recovery or carry-over action:
the first part takes place underwater
the exit of the arm is favored by the roll of the shoulders
during the flight the arm is extended and relaxed
the hand rotates to let the little finger enter first, in order to favor a more hydrodynamic "hand entry and to allow the hand to go immediately and better in grip
the outstretched arm enters the water over the shoulder

2) Underwater action:
it is distinguished in: support / grip, traction and thrust;
the action of the hand develops according to a curvilinear trajectory both to take advantage of the upward thrust (Bernoulli's principle), and to find still water by changing the direction of application of the force;
at the end of the support phase the elbow flexes to take advantage of a more advantageous lever and to develop an action more parallel to the line of advancement;
the elbow in the traction phase must be low with respect to the hand to make the hand perform a useful rowing action and also to involve the forearm in the thrust.

Lower limb movement

The propulsive action takes place in the movements from the bottom to the top
The whole limb is involved in the stroke, from the hip to the feet
The action must develop completely underwater
Depth: 20/30 cm children, 40/50 cm adults
The flexion of the leg on the thigh can form an angle of 100/110 degrees
The foot, in the ascent, is naturally extended and rotated inside.

Upper and lower limbs relationship

For each stroke cycle usually 6 or 4 foot strokes develop
The function of the legs is mainly propulsive
The range of movement of the legs is considerable (greater than that of the crawl), with the possibility of forming a very advantageous angle for the thrust between the leg and the thigh.