Body Position and Physics

While swimming, it is important to realize what each body part is doing and where it is moving.

The push-off: While pushing off the wall, the body should be submerged and facing the bottom of the pool. The hands should be together and stretched out in front. The biceps, pressed against the ears, head stationary and perpendicular to the body. The swimmer should be flat and streamline in the water, with the feet swept back. The push-off is the same for all the strokes, except the backstroke. In this situation, the body is instead facing the ceiling of the pool.

Physics: As the body assumes a streamline position and is forced off the wall, the sleeker the body, the less drag produced. If any of the characteristics listed above change, a greater drag-force is applied to the body, thus slowing the swimmer down.

When the body begins to loose speed and float to the surface, the kick and first stroke is applied. The kick helps propel the body through the water, while the stoke helps pull it.

The stroke: Each stroke and pattern is unique. The crawl stroke uses a flutter kick and an ‘S’ stroke to propel the body. The butterfly uses the dolphin kick and a ‘key-hole’ stroke. The back uses the same flutter kick as the crawl, but uses an out-sweep 'L' stroke. The breaststroke uses the breaststroke kick and a scooping motion for its pull.

Physics: Each stroke has a catch, power phase, and recovery. The physics of each stroke is similar so only the freestyle will be explained and the others will be related to it.

Freestyle begins with the catch, a motion which allows the swimmer's hand to engage the water. The power and stroke length of the entire pulling pattern is achieved at this point. As the arm enters the water, two things happen. First, the body rolls downward to the same side. Second, the shoulder pushes forward from the chest. These two movements mimic a person stretching to reach something beyond grasp. At this point the arm rolls counterclockwise and sweeps outward, using the latissimus muscle. When preformed correctly, a solid feel of water pressure against the hand is experienced. The power phase of the stroke drives the arm inward and backward to the hip. This creates an ‘S’ shape. Finally, the recovery brings the hand back to the catch phase of the pulling pattern. This is done by using a high elbow position, which helps the opposite arm during its power phase (Thompson). Each stroke uses this same motion, however; each stroke creates different movements and different forces in the water.

The turn: As the body approaches the wall at the other end of the pool, a turn must be maneuvered. For freestyle, the second to last stroke ends at the hip and stays there while the body follows the last stroke into a summersault. When the body rotates, a tight ball is used to make the turn quick. Physics tells us that as an object is rotating, velocity is increased as the moment of inertia is decreased (i.e. the smaller the sphere, the faster the velocity of the turn). When the summersault is halfway done, or the body has rotated 180 degrees, the feet are extended to the wall and the push-off from the wall propels the body into another cycle.

Index Back Next