Original text - Engels - The lead arm (recovery arm) should ...

The lead arm (recovery arm) should stretch in front of the head of the swimmer as the propulsion arm pushes backwards.

The amplitude of the leg kick should be as small as possible for a given power requirement, since increasing kick amplitude increases frontal surface area and, therefore, form drag.

The body must maintain good alignment with the direction of swim; any pitch or yaw of the body will increase the frontal surface area and increase form drag.