Natural forces affect the movements of swimmers in water. And it is often usefulto know how these forces act. This knowledge will help swimming teachers andcoaches analyze swimming skills and assist them to understand how these forcesinfluence movement, so that they can encourage beginners to be better swimmersor good swimmers to achieve there optimum potential. Biomechanics is the branchof science that is concerned with understanding the relationship between aliving body’s structure and function relative to movement. In this paper theswimming form of the front crawl stroke will be analyzed, which may result inimprovement in the following areas: Improving performance Preventinginjury Correcting weaknesses Identifying ways to alter human movementpatterns “Biomechanics is considered to be the physics of how the bodymoves.
When these physical principles are applied to sports skills it becomes anintegrated study between the internal forces produced by the body and thenaturally occurring external forces that act on the body as skills are executed(Carr, 1997, p4.)”. Although the final quality of movement will totallydepend upon the athlete’s (swimmer’s) ability to integrate both internal forcesgenerated by muscular actions with the external forces of gravity, buoyancy,fiction and mass that are present during swimming.
When looking at swimming onemust first look at how the human body acts and generates forces in water.
“Water is a unique environment. It possesses qualities that will assist theswimmer, but it also has qualities that will impede the swimmer’s progressthrough the water. For instance, the water’s density provides a buoyant forcefor the swimmer, while at the same time providing resistance to the swimmerspropulsion (?????, 1995, p42)”. Topics to continue with: Main principlesand their application Density Water Resistance Skin/Frictional ResistanceFrontal/Wave Resistance Eddy/Turbulence Resistance Propulsion Water FrictionPropulsive Drag Lift Force Streamlining The main principles and theirapplication of the front crawl stoke Buoyancy ; Flotation An object that isimmersed either totally or partially in water experiences an upward force as thewater’s density endeavors to stop it from sinking (Maglischo, 1982). This upwardforce is known as the buoyant force and acts through the center of the displacedwater. This force therefore, tends to counteract the effect of gravity and theweight of the object, the net result being that the weight of the object isreduced by the upward force of buoyancy (Costill, 1992). (#Diagram#) Everyobject has an absolute center position where all forces exerted by the bodyequal zero. This central point of an object’s mass is known as the center ofgravity and is the point around which it balances. “The center of gravityis approximately 50-52% of an individuals height, as there is an equal spread ofmass above and below this point (Allen, 1999)”. The same can be said forthe center of buoyancy, as above and below this point there is an equal spreadof volume of the displaced water (Allen, 1999). The location of the center ofbuoyancy which is the center of the water displaced by the body, is actuallycloser to the head than in the location of the center of gravity. The reasonsfor this are: The volume of water displaced has a greater mass then the chestarea. The chest has a lower density than the water because of its lungcapacity. Therefore the upward force of buoyancy acts thought a point higher upthe body than the center of gravity (Costill, 1992). (#Diagram#) (I may need toinclude more?) (And relate it back to the front crawl?) Density The termspecific gravity is used to describe the ratio between an object’s density tothat of water’s density. “Pure water density being the “referencepoint” having a specific gravity of 1.00 (Carr, 1997, p67)”. Thereforeanything placed in water will float or sink in accordance to it’s own specificgravity value. Anything greater than 1.00, will sink. While anything less than1.00 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 andmuscle are heavier than fat. From this information one can assume that a leanand muscular body or one with a heavy bone structure, will not float as well asone that is the opposite. (Chart #1.) Relationship between Specific Gravity& Body Composition Studies have shown that: “in general, the specificgravity of women will be less than that of men, and that of children will beless than that of adults, especially at ages when the trunk is a greaterproportion of the total body mass” (Adrian & Cooper, 1989). (Chart #2.)& (Diagram The human body in water) Water Resistance In all the strokes usedin swimming there is resistance. As swimmers move through water, they should aimto minimize resistance. In the front crawl action there are three major forms ofresistance they are: Skin, or frictional resistance Frontal or waveresistance Eddy or turbulence resistance. (Diagram of the front crawlresistance) Skin or Frictional Resistance In the action of the front crawl, thisform of resistance occurs because “new” water is always rubbingagainst the swimmer’s body. One way this could be significantly lowered would beif the body could carry on its surface a very thin layer of surface water. Thisphenomenon naturally occurs in under water animals such as dolphins and sharks.
This is the same type of concept which occurs on golf balls due to the dimpledsurface (Wilmore). To improve the resistance in the front crawl action swimmerscan try to make their bodies as smooth as possible. Some examples of this areseen in the close fitting swimwear, oiling the skin and shaving the body andhead. In the front crawl action the magnitude of the surface friction will bedetermined by: The speed of water relative to the swimmers speed Theamount of surface area of the body The smoothness of the body Thequalities of the water (Maglischo, 1982) (#Diagram#) Frontal or Wave ResistanceIn the action of the front crawl the body is propelled forward through thewater. This creates a wave or wall of water, which swells up in front of thebody. “These waves can have a powerful retarding effect and the retardationincreases as the swimmer’s velocity increases (?????)”. It should be notedhow ever, that this wave also assists in the front crawl action as the swimmerbreaths behind the wave formed by the head, thus keeping the head level andbeneath the water line. “The net effect being, that swimmers are able toconserve energy and still maintain a streamlined body position throughout thestroke (Costill, 1992, pg.48)”. The effect of frontal resistance changescontinuously according to stroke technique. The difference in depth of the areacovered by the body during the action of the front crawl (Maglischo, 1982).
(#diagram# Front crawl bow wave) Eddy or Turbulence Resistance “Water leftundisturbed will flow evenly and in a laminar state (Maglischo, 1982,pg.12.)”. However, swimmers inevitably disturb the water that they aremoving through. This effect can be reduced by keeping the body streamlined,disturbing a minimum quantity of water, thus keeping the water in a laminarstate. (#Diagram of Form Drag#) Laminar flow reduces resistance because thewater molecules slip past the streamlined body with minimum change in speedand/or direction. This is not the case if there is an obstruction in the path ofthe water. In this situation, the water molecules slow down and push against theleading surface thus creating a high pressure in front of the object (Maglischo,1982). At the same time the water cannot change direction quickly enough behindthe object as it moves through the water. This turbulance has a low pressure andis characterised by eddies and moving water (Maglischo, 1982). A good example ofthis situation is shown by the bow wave in front of the head and the turbulenceof water that is behind the head and down the back of swimmers as they moveforward through the water in the front crawl. The whirling currents are areaswhere the water is unstable and the lower pressure area that has been developedwill create a suction effect to reduce the forward motion by pulling the bodypart or parts back. (#Diagram Eddies around the body#) Eddy turbulance can becaused by poor stroke technique or by having a poor streamlining position in thewater. Examples of these errors in the front crawl are: Poor hand and armentry in the water. Leg kicking with a large knee bend. A deep hollow inthe back, which raises the hips too high. (Maglischo, 1982) The human body isnot adapted to moving freely through water, due to its large flat areas androunded limbs. This leads to turbulence being an unavoidable force in thesimming action that is the front crawl. The magnitude of eddy turbulence howeverwill depend upon: The cross sectional width of the body part that is movingperpendicular to the flow of water. The shape of the body parts. Thesmoothness of the surface. (Costill, 1992) Streamlining: Reduced resistance.
Eddy Turbulence: Suction effect on the back. Pressure on the front pushes theobject back. (#Diagram Eddy Resistance ; Eddy Turbulence#) Propulsion Actionof the Front Crawl The Arm Stroke Entry ; Stretch Down sweep ; catch Thein sweep The upsweep Release ; Recovery Timing of the Arms The Flutter KickDown beat Up beat Kick Width Lateral Kicks Is the Kick Propulsive? Body PositionHorizontal Alignment Lateral Alignment Breathing Timing of the Arms ; Legs 6Beat kick 2 Beat kick 2 Beat cross over kick 4 beat kick Breathing Patterns 25m- 50m 100m Longer Distances Variations in StyleBibliographyAnthony, C. and Thibodeau, G. 1987. Anatomy and Physiology, 12th Edn. St.
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Philadelphia, Saunders College Publishers. Howard, G. Knuttgen, J and Vogel, J.
1983. Biochemistry of Exercise, 5th Edn. Champaign, Human Kinetics Publishers.
Marieb, R. 1998. Human Anatomy and Physiology, 4th Edn. California, BenjaminCummings. McArdle, W. Katch, F and Katch, V. 1996. Exercise Physiology: Energy,Nutrition and Human Performance, 4th Edn. Baltimore, Williams and WilkinsPublishers. Sharkey, B. 1975. Physiology and Physical Activity, New York, Haperand row Publishers. Strand, F. 1983. Physiology: A Regulatory Systems Approach,2nd Edn. New York, MacMillian Pulishers. Weller, H. 1985. Basic HumanPhysiology, Boston, Prindle, Weber and Schmidt Publishers.
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Swimming And Biomechanics. (2019, Apr 19). Retrieved from https://graduateway.com/swimming-and-biomechanics/