Physical laws in swimming

Definition

With physical laws, we try to improve and optimize the individual swimming styles even further. These include static buoyancy, hydrodynamic buoyancy and the various ways of moving around in the water. It uses biomechanical principles and physics.

Static buoyancy

Almost everyone manages to drift on the water surface without any buoyancy aid. This apparent weight loss is due to the static buoyancy. For example, if a body dips into the water, it displaces a certain mass of water.

In this process, a buoyancy force (static buoyancy) acts on this body. For example, in water it is possible to have a squat swimmer lifted effortlessly by a much weaker person. If a part of the body of the person carried is lifted out of the water, the static buoyancy decreases and lifting becomes more difficult.

Deep inhalation increases the lung volume and thus the total body volume and the static buoyancy is increased. For example, a float in suspension exhales and sinks to the bottom. The decisive factor for the buoyancy of the body in water is therefore the specific weight (density of the body).

The higher the density of the body, the more the body sinks in the water. Athletes with heavy bones and many muscles have a higher density and sink much more, and therefore have disadvantages when swimming. Women have more subcutaneous fat tissue than men, and therefore have greater static buoyancy and a better position in the water.

  • The static buoyancy corresponds to the weight force which the body displaces at water mass
  • The static lift is opposite to the weight force. (upwards)

Static buoyancy and water position

The water position is crucial for fast and long swimming. 2 physical points of attack are important for the correct water position. On the one hand the body center of gravity (KSP) and the volume center of gravity (VMP).

The CSP of the human body is located approximately at the height of the navel and is the point of attack for the downward weight force. The VMP is the point of attack for the static buoyancy and is approximately at chest height due to the voluminous ribcage. In the water, KSP and VMP are shifted one above the other.

For example, a cuboid (half polystyrene, half iron) does not lie on the surface of the water, but the metal half sinks, and the cuboid stands upright with the polystyrene side facing upwards. Similar to the cuboid, this principle works with the human body. CSP and VMP approach each other and as a result the legs sink and the body stands increasingly vertical in the water.

Important! Legs hanging too low in the water do not create propulsion and increase the water resistance, i.e. à legs to the surface. To prevent the legs from sinking, it is recommended to use diaphragm/abdominal breathing instead of chest breathing to keep the VMP as close as possible to the CPD, and to keep the head in the water and stretch the arms far forward. This will result in a shift of the CSF head towards the VMP.