© 2008 McGraw-Hill Higher Education. All Rights Reserved. Chapter 20: Locomotion: The Aquatic...

© 2008 McGraw-Hill Higher Education. All Rights Reserved.

Chapter 20:Chapter 20:Locomotion:Locomotion:The Aquatic EnvironmentThe Aquatic Environment

KINESIOLOGYScientific Basis of Human Motion, 11th edition

Hamilton, Weimar & Luttgens

Presentation Created byTK Koesterer, Ph.D., ATCHumboldt State University

Revised by Hamilton & Weimar

KINESIOLOGYScientific Basis of Human Motion, 11th edition

Hamilton, Weimar & Luttgens

Presentation Created byTK Koesterer, Ph.D., ATCHumboldt State University

Revised by Hamilton & Weimar


ObjectivesObjectives

1. Name those factors that contribute to the propulsion of a swimmer.

2. Name those factors that impede the progress of a swimmer.

3. Explain how the propulsive and resistive factors named affect the length or frequency of the swimming stroke.

4. Complete a kinesiological analysis of a swimming stroke, identifying the anatomical and mechanical factors for success in the selected stroke, as well as those factors that limit the performance.


AQUATIC LOCOMOTION: AQUATIC LOCOMOTION: SWIMMINGSWIMMING Differences between locomotion in

water and on land:1. The body is concerned with buoyancy

rather than with the force of gravity.2. The substance against which it pushes

affords less resistance to push.3. The medium through which it moves

affords more resistance to the body.4. Customary to maintain a horizontal rather

than vertical position.


SwimmingSwimming Initial mechanical problem is to overcome

inertia. Once the body is in motion, the problem is to

overcome the forces that tend to hinder it. Water is both the supporting medium and the

source of resistance. Hands and feet depend on reaction force of

water to transmit force to the body. At the same time, the body must overcome

the resistance of the water.


Speed in SwimmingSpeed in Swimming

Depends on stroke length and stroke frequency.

Stroke length depends on forces that produce forward motion and resistance of water in opposite direction.

Actions of the arms and legs result in a combination of lift and drag forces that propel the body forward.


Drag and LiftDrag and Lift

Arm and leg motions result in a combination of lift and drag forces that propel the body forward.

Fig 20.1


Fluid ResistanceFluid Resistance

Form drag: resistance due to surface area of the front of the body.

Surface drag: resistance of the water next to the body.

Wave drag: occurs at the surface as the body moves along.

Turbulence: forms behind the body.


Stroke FrequencyStroke Frequency

Depends on the amount of time spent per stroke cycle.

Related to the nature of the stroke pattern and the muscle torques of the arms and legs.


Mechanical Principles Mechanical Principles Applied to SwimmingApplied to Swimming

1. Swimming should produce an even progress through the water rather than cycles of speeding up and slowing down.

2. The body will move in the opposite direction from that in which the force is applied.

3. Forward motion is produced through a combination of drag force and lift force.

4. Maximum force is attained by presenting as broad a surface as possible in the propulsive movements of the limbs and by exerting a backward pressure through as great a distance as possible.



5. Momentum may be transferred from one body or part to another body or part as momentum is conserved.

6. The height of the body position in the water depends on the swimmer’s buoyancy and speed of moving through the water.

7. When a body is free in a fluid, movement of a part in one direction results in movement of the rest of the body in the opposite direction.

8. A rapidly moving body in the water leaves a low pressure area immediately behind it.



9. The more streamlined the body, the less the resistance to progress through the water.

10. The drag on the body in any fluid increases approximately with the square of the velocity.

11. The sudden or quick movement of a swimmer’s body, or one of its parts, at the surface of the water tends to cause whirls and eddies that create drag.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlHead and TrunkHead and Trunk

Three important functions:1. Minimize resistance.

2. Enable the swimmer to breath.

3. Provide a stable anchorage for the arm and leg muscles to effect a maximum propulsive force.



Body is as horizontal as possible. Feet below the surface. Head breaking the water at the hairline.

Static contraction of rectus abdominis holds spine in a slightly flexed position, or prevents extension.

Pelvis is in a position of slightly decreased inclination.



Lateral movements of the trunk will increase resistance to forward movement. Circular movements of the arms, legs or head

cause a counter movement of the rest of the body.

Turning the head to breathe must be accomplished with the least possible interference. Do not lift the head to breathe. Rotate it while tucking the chin.



After a quick inhalation, face is turned forward.

Breathe every stroke for distance events, and less often for sprints.

By alternating actions of the left and right oblique abdominals and spinal extensors, the spine and pelvis are stabilized against the pull of the shoulder and hip muscles.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlArm Stroke: Entry and SupportArm Stroke: Entry and Support

Entry should place the arm in the most advantageous position for exerting force. Forearm high and elbow pointing to the side. Hand passes in front of shoulder, reaches forward,

and is driven forward and downward into the water directly in front of the shoulder.

Elbow is slightly flexed, and extends during entry.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlArm Stroke: Entry and SupportArm Stroke: Entry and Support The brief moment between entry and

the beginning of the propulsive action is called the support phase. Purpose is to keep the head and shoulders

high in the water. Pressure of forearm and hand is mostly

downward and then backward, producing and upward and forward reactive force.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlArm Stroke:Catch, Pull, and PushArm Stroke:Catch, Pull, and Push Catch: propulsive action changes from

downward to backward. A quick inward movement of the hand and arm

that serves to bring the hand to a position in front of the axis of the body.

The pull phase begins with the first backward motion of the hand. Upper arm is vertical, and favors use of the large

muscles - pectoralis major and latissimus dorsi for pulling downward and backward.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlArm Stroke:Catch, Pull, and PushArm Stroke:Catch, Pull, and Push Pull: elbow should be kept high during

the first part of the pull. By bending the elbow the arm is pulled

under the body. Maximum bend occurs halfway through the

pull, when the hand begins to push water backward.

Elbow action assists in producing an S-curve, which creates propulsive lift.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlArm Stroke:Catch, Pull, and PushArm Stroke:Catch, Pull, and Push Push: transition from pull to push occurs as

the arm passes under the shoulder. As forearm passes the front of the hip, the upper

arm extends and the hands gives a quick push backward.

Release and Recovery: Pressure is relaxed, elbow & shoulder raised out of the water. Elbow swings forward and upward with hand trailing behind. Hand moves in front of shoulder ready for next entry.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlThe Kick: Nature Of MovementThe Kick: Nature Of Movement Most often used is the flutter kick. Primary role is a stabilizer and neutralizer.

Timing with arms is therefore critical.

Legs are relatively close together as they alternate in an up and down movement. Feet attain a maximum stride of 1 to 2 feet. Whiplike or lashing action for both the up and

downstroke.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlThe Kick: DownstrokeThe Kick: Downstroke Begins with downward drive of the

thigh. Thigh flexes only slightly, knee extends

completely by the end of the stroke. Ankle and foot remain in plantar flexion.

Dorsiflexors contract statically to stabilize foot against pressure of the water.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlThe Kick: Upstroke The Kick: Upstroke Begins with thigh extension. Slight knee flexion develops near the

end of the stroke. Foot stops just below the surface.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlStroke CoordinationStroke Coordination

Six beat kick for every arm cycle. Uneven number of leg beats for each arm serves

to maintain balance around vertical axis. Breathing occurs on one side.

Head is turned with chin toward axilla. Inhalation only when head turns. Exhale under

water. As velocity increases, arm cycles will move

closer together, so that entry of one arm occurs as other is finishing push.


Analysis of the Sprint CrawlAnalysis of the Sprint CrawlAdditional Factors Additional Factors Relaxation of the body. Flexibility of the joint.

Shoulders and ankles.


Fig 20.2

Sprint Crawl StrokeSprint Crawl Stroke


ROWINGROWING Much of the propulsive force is

generated by the legs. Two distinct phases:

Pull phase Recovery phase


ROWING: ROWING: Pull PhasePull Phase Force applied to the water by the oar

blade. Initiated through extension of flexed

lower extremities, followed by trunk extension and then upper extremity pull.

Fig 20.3c


ROWING: ROWING: Recovery PhaseRecovery Phase Blade lifted clear of water by downward

pressure on the grip. Oar is feathered to slice through the air. Legs and trunk are flexed and upper

arm extends.

Fig 20.3a


CANOEINGCANOEING

Paddle is held in both hands. Stroke is primarily performed by the

arms, shoulders, and trunk. Paddler faces the direction of travel. Stroke involves reaching out either in a

forward or sideward direction and pulling the paddle blade through the water.


CANOEINGCANOEING

The beginning of the stroke produces a downward force and a lifting effect.

The end of the stroke produces an upward force that depresses the canoe.

Smooth canoeing emphasizes the backward movement of the blade.


Techniques for Steering the Techniques for Steering the CanoeCanoe

Fig 20.4


KAYAKINGKAYAKING Kayak rides lower in

the water than other boats.

Uses a double bladed paddle, set perpendicular to one another.

Can effectively stroke on both sides in a cyclic fashion.

Fig 20.5


Chapter 20:Chapter 20:Locomotion:Locomotion:The Aquatic EnvironmentThe Aquatic Environment

© 2008 McGraw-Hill Higher Education. All Rights Reserved. Chapter 20: Locomotion: The Aquatic...

Documents

Transcript of © 2008 McGraw-Hill Higher Education. All Rights Reserved. Chapter 20: Locomotion: The Aquatic...