Symmetry plays an important role in swimming. If a body and its motion are not symmetrical, the body tends to move in the direction with greater force. For example, a person who pulls hard on the right side will move in a counterclockwise circle. A good swimmer balances the body, the forces exerted, and the forces produced by the body. An imaginary line that passes down the center of the face and ends between the legs is the most common line of symmetry. Nothing on the right-hand side of the body should ever cross into the left-hand side and visa versa. For freestyle, before the power-phase the arm rotates counterclockwise and then sweeps outward. A common mistake is for the arm to rotate clockwise and them pull, which unfortunately causes the arms to pass the line of symmetry.
When the arms break this line of symmetry, the arms are now pulling water that is disrupted by the body itself, and leads to a very inefficient stroke. The arms that pull to the outside of the body are pulling water that is not disturbed by the body, leading to a greater force applied.
Swimmers also get into a rhythm with their kicking
and pulling. A swimmer with a set rhythm and lots of practice will use less
energy to travel the same distance as a swimmer with no rhythm. If you’ve
ever seen an Olympic swimmer, you will notice a set rhythm, however, compare
them to a beginner and an obvious difference in the rhythm will be noticed.