Swimming Bio Mechanics

This essay has a total of 1746 words and 12 pages.

Swimming Bio Mechanics

Natural forces affect the movements of swimmers in water. And it is often useful to know how these forces act. This knowledge will help swimming teachers and coaches analyze swimming skills and assist them to understand how these forces influence movement, so that they can encourage beginners to be better swimmers or good swimmers to achieve there optimum potential. Biomechanics is the branch of science that is concerned with understanding the relationship between a living body's structure and function relative to movement. In this paper the swimming form of the front crawl stroke will be analyzed, which may result in improvement in the following areas:

Improving performance
Preventing injury
Correcting weaknesses
Identifying ways to alter human movement patterns

"Biomechanics is considered to be the physics of how the body moves. When these physical principles are applied to sports skills it becomes an integrated study between the internal forces produced by the body and the naturally occurring external forces that act on the body as skills are executed (Carr, 1997, p4.)". Although the final quality of movement will totally depend upon the athlete's (swimmer's) ability to integrate both internal forces generated by muscular actions with the external forces of gravity, buoyancy, fiction and mass that are present during swimming.

When looking at swimming one must first look at how the human body acts and generates forces in water. "Water is a unique environment. It possesses qualities that will assist the swimmer, but it also has qualities that will impede the swimmer's progress through the water. For instance, the water's density provides a buoyant force for the swimmer, while at the same time providing resistance to the swimmers propulsion (?????, 1995, p42)".

Topics to continue with: Main principles and their application
Water Resistance
Skin/Frictional Resistance
Frontal/Wave Resistance
Eddy/Turbulence Resistance
Water Friction
Propulsive Drag
Lift Force

The main principles and their application of the front crawl stoke

Buoyancy & Flotation

An object that is immersed either totally or partially in water experiences an upward force as the water's density endeavors to stop it from sinking (Maglischo, 1982).

This upward force is known as the buoyant force and acts through the center of the displaced water. This force therefore, tends to counteract the effect of gravity and the weight of the object, the net result being that the weight of the object is reduced by the upward force of buoyancy (Costill, 1992). (#Diagram#)

Every object has an absolute center position where all forces exerted by the body equal zero. This central point of an object's mass is known as the center of gravity and is the point around which it balances. "The center of gravity is approximately 50-52% of an individuals height, as there is an equal spread of mass above and below this point (Allen, 1999)". The same can be said for the center of buoyancy, as above and below this point there is an equal spread of volume of the displaced water (Allen, 1999).

The location of the center of buoyancy which is the center of the water displaced by the body, is actually closer to the head than in the location of the center of gravity. The reasons for this are:
The volume of water displaced has a greater mass then the chest area.
The chest has a lower density than the water because of its lung capacity. Therefore the upward force of buoyancy acts thought a point higher up the body than the center of gravity (Costill, 1992). (#Diagram#)
(I may need to include more?) (And relate it back to the front crawl?)


The term specific gravity is used to describe the ratio between an object's density to that of water's density. "Pure water density being the "reference point" having a specific gravity of 1.00 (Carr, 1997, p67)". Therefore anything placed in water will float or sink in accordance to it's own specific gravity value. Anything greater than 1.00, will sink. While anything less than 1.00 will float. In the human body there is variation from person to person, this is due to the amount of air in ones lungs and the percentage of bone, muscle and fat, which all vary in their own individual masses. Both bone and muscle are heavier than fat. From this information one can assume that a lean and muscular body or one with a heavy bone structure, will not float as well as one that is the opposite.
(Chart #1.) Relationship between Specific Gravity & Body Composition
Studies have shown that:
"in general, the specific gravity of women will be less than that of men, and that of children will be less than that of adults, especially at ages when the trunk is a greater proportion of the total body mass" (Adrian & Cooper, 1989).
(Chart #2.) & (Diagram The human body in water)

Water Resistance

In all the strokes used in swimming there is resistance. As swimmers move through water, they should aim to minimize resistance. In the front crawl action there are three major forms of resistance they are:
Skin, or frictional resistance
Frontal or wave resistance
Eddy or turbulence resistance.
(Diagram of the front crawl resistance)

Skin or Frictional Resistance

In the action of the front crawl, this form of resistance occurs because "new" water is always rubbing against the swimmer's

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