Forces in Swimming:
There are several forces that act upon the movement of a human body as it travels through water - these forces are drag, lift, gravity and buoyancy. Drag and lift are the main propelling forces that are used by the swimmers while swimming. Resistance (also known as drag) can be broken into three main groupings: Frontal resistance, skin friction and eddy resistance. Buoyancy in swimming can be best described by Archimedes’ principle: a body fully or partially submerged in a fluid is buoyed up by a force equal to the weight of the fluid that is displaced by the body – this essentially negates any effects that gravity may have on the swimmer.
Frontal Resistance:
Frontal resistance occurs when the body rides too low in the water; essentially producing a larger surface area that pushes against the water in the direction opposite of forward motion. To limit the effect of frontal resistance, the swimmer tries to position themselves as high on the water surface as possible to produce an effect that is similar to a hydrofoil. In conjunction with this, the swimmer will roll their body from side to side as the swim strokes are executed. This turning movement will help keep the body higher in the water.
Skin Friction:
Skin friction is the kinetic friction of the swimmer’s skin and suit with the water. This can be dealt with in a number of ways – the most popular method/option is to either shave or wax all visible body hair. When a swimmer shaves or waxes their body hair, they decrease the surface area of their skin. A similar result can be achieved through the design of the racing suits which mimic characteristics of shark skin. The surface of the suit is constructed with a series of ridges that tend to reduce drag when it passes through the water because the ridges act to deflect water away from the surface of the suit.
Eddy Resistance:
Eddy resistance is caused by poor stroke technique and riding too low in the water (frontal resistance). The water is unable to fill in instantly behind the swimmer – causing them to pull water and air bubbles along with them; slowing them down. Whenever a swimmer executes a front crawl stroke, an eddy shaped as a vortex or whirlpool, forms at the water surface. If the stroke isn’t executed properly, the vortex will remain. If the vortexes accumulate around the body of the swimmer, the water resistance is increased.