As the hand continues its propulsive motion rearward and enters the back quadrant, past the shoulder, to get from 6 o’clock to 9 o’clock, it takes a different course than going around the perimeter of the glare clock. To maximize the propulsive power of each arm pull, the force vector of the arm/hand needs to remain in the opposite direction of the body’s motion. To accomplish this, rather than follow the perimeter of the clock, which would create an upward force, increasing frontal drag, the hand elevates and the wrist dorsiflexes to maintain the maximum surface area possible pushing backward. In other words, the hand cuts off much of the quarter of the clock when going from 6 to 9 o’clock.
Since the hand/arm loses power biomechanically as it moves rearward into the back quadrant, several things happen in order to help sustain the propulsive force. First, the hand elevates and the wrist dorsiflexes to keep the maximum surface area pushing backward. Second, the upper arm tucks into the swimmer’s side creating some motion backward of that part of the arm with a resultant propulsive force. Third, as a result of the body coming to the end of its counter rotation during this phase and stopping its motion to initiate a new rotation in the opposite direction, the stabilizing force from the body rotation is now minimized. To replace that force, the most powerful of the three down kicks that happen during the underwater pull (with a 6 beat kick), occurs toward the side of the pulling arm, as the body is now rotated to this same side, and coincides with this final propulsive phase of the pull. This hard kick now acts as the primary stabilizing force for this phase of the pull and enables the swimmer to maximize all of the power possible from this weaker back quadrant pulling position.
By the time the hand reaches 9 o’clock and it is near the hip, the elbow is now nearly fully extended and there is no longer any propulsive power available to gain from that arm pull. At this moment the body speed is as fast as it will get during the stroke cycle, primarily because the propulsive phase has just ended and the position of both arms (one out front and the other behind) reduces the drag coefficient to its lowest point. It is now time to get the hand back into the front quadrant as quickly and efficiently as possible in order to start another freestyle swimming pull.
Yours in swimming,