Abstract
A stoke of the back crawl stroke in the current competitive swimming is a style in which a hand palm moves on the character of S on the side of the body. In this study, the hand path of the back stroke was calculated with a physical model using experimental results of hand palm aerodynamic characteristics. The stroke path of the maximal efficiency and that of the maximal thrust force were obtained as drive angles, tilt angles and angles of attack. As a result, the stoke of the maximal efficiency is the conventional S-shaped stroke and that of the maximal thrust is the I-shaped stroke in which a hand palm moves parallel to the body axis towards legs with using only drag force.
