Biomechanics Biomechanics of of

SwimmingSwimming

Swimming• Stroke: physical movements through the

water– Measured in rate and length

• Start: dive position, hand grip on block, breathing pattern in preparation, dive depth

• Turn: use of inverted positions, pressure off the wall, underwater preparatory time/depth

How do we assess a swimmer?

• Stroke length– Stroke length increases on distance events

• Stroke frequency

• Velocity – Rate and velocity typically decline over the

course of a race

• Sprinting speed – Force and efficiency

Swimming Speed and Efficiency

• Factors influencing swimming velocity– Stroke length– Stroke frequency

Swimming = Stroke x Stroke

Velocity Length Frequency

V = SL x SF

• Swimming efficiency – Ratio of mechanical work performed to energy

expended to do work as determined by VO2

• Total efficiency is divided into– Mechanical (propulsion) efficiency

• Ratio of power used to overcome drag over power expended in performing movements

– Metabolic efficiency• Ratio of power used to perform movements to

power consumed by swimmer

Swimming Speed and Efficiency

Swimming Stroke

• Front crawl

• Backstroke

• Breaststroke

• Butterfly

Front Crawl

Front Crawl•Hand performs insweep for propulsion (catch phase), this motion rotates below the the body, behind and up for recovery•4-6 beat kick with slight ankle flexion•Body roll during pull-through•Breathe every, every 3rd or 5th stroke

Front Crawl

• “Freestyle”

• Consist of right and left armstroke and

varying number of kicks

– Armstroke

– Flutter kick

– Body position and breathing style

– Rhythms between arms and legs

Armstroke

• Phases of armstroke– Propulsive phases

• Downsweep • Catch• Insweep• Upsweep

– Recovery phases• Release and recovery • Entry and stretch

Entry and Stretch

• Hand enters water in streamlined manner

• Arm moves forward

• Easy to produce wave drag

Downsweep and Catch

• Downsweep– Beginning of propulsive phases– to position arm for propulsive sweep– Sweep down in curvilinear path

• Catch– Take place near the end of downsweep– Palm is rotated outward

Insweep

• The first propulsive sweep

• Arm travels under body to midline

• Sculling movement

• Hand don’t travel at max velocity

Upsweep

• Final propulsive sweep

• Hand is rotated out quickly

• Hand accelerates to max velocity

Release and Recovery

• Hand leaves water

• To place arm in position for another underwater stroke

• Goal of recovery– To get arm over water with the least

disruption of lateral alignment– To provide short period of reduced effort for

arm, shoulder and trunk muscles

Propulsive Movements by Hands-Arms

• Two methods for moving hand-arm unit– Paddling method ; using drag force

Propulsive Movements by Hands-Arms

– Sculling method ; using primarily lift force

Propulsive Drag Force

Propulsive Lift Force

Flutter Kick

• Primary directions are up and down– Upbeat– Downbeat

• Propulsive phase of kick

– To counteract tendency of body to be pushed up or to side by movements of arms

BreaststrokeBreaststroke

Breaststroke

•Broken into outsweep, insweep, recovery•Outsweep initiates at midline, moving laterally 12-15 inches, rotates into an insweep towards the chest•Kick: knees and hips flex as the feet are drawn toward the body, feet turn outward to generate propulsion and surface area; knees slightly wider than hips

Phases

• Divided into 4 phases

– Glide/Post-thrust

– Breathing

– Recovery

– Pre-thrust

Glide/Post-thrust

Arm Action Leg Action

Body Position

• Streamline in stroke and

in pulldowns

• Shoot the hands forward

so that when they kick

they are already going

into the streamline

Breathing

Recovery

Body Position

• For every inch the head is lifted, the hips sink two inches

• For every inch above the surface the head is lifted, it will take additional time to get to the streamline position

Pre-thrust

Leg Action

• Types of kick– Frog kick

• Legs are drawn, knees turn outward and separate more than feet

• Knees rotate inward as soles thrust outward backward

– Whip kick• Knees drop and separate as heel• Feet turn outward as leg whip out and back

Butterfly Stroke

•“s” insweep of the arms with full lateral extension, typically wrists relaxed in unison movement•Coordinated undulation of the body•Legs in a two beat unison kick, knees extend slight ankle flexion (down beat stronger than second kick)•Breathe either every, or every other stroke

Dolphin Kick

• Flow travels along dorsal surface of foot• Magnitude of propulsive force depends on

– Propulsive lift force– Resistive drag– Rate of kick– Forward speed of body and legs

• Initiated from thoracic spine• Eel-like movement of total body

Streamlining Technique

• First streamlining technique– Enter with hands at shoulder width as the first

kick is executed– Downbeat dolphin kick serves to set body and

hips high– Propulsive force generated by arms

Streamlining Technique

• Second streamlining technique– First-half of propulsive stroke cycle– Arms are positioned to deliver max drag– Stretch legs up during propulsive phase

Streamlining Technique

• Third streamlining technique– Recover legs during the arm recovery– Trunk is positioned closer to horizontal– Conserving forward momentum– Second dolphin kick serves to support hips

Vortex Theory of Propulsion

• Possibility of swirling masses of water

• Vortex formed beside tail portion

Sweeping Pattern

• There are 3 or 4 sequences of sweeping movements

Sweeping Pattern

• Hands enter water at shoulder width with palm slightly outward– Angled hand entry allows smooth transfer of

momentum developed during arm recovery

• Then, hands sweep inward as moving under the trunk– Drag propulsion is generated on hand/arm

surface

Sweeping Pattern

• Final propulsive sweep moves hands out of water and into recovery phase

• Hands movements are rounded

• Hand speed continues to accelerate

Backstroke•Propulsion generated by adduction of the arms and internal rotation of the upper body•Body roll as a key factor•4 or 6 beat kick•Flexion and extension of knee & ankle; gluteal engagement

Body Position

• The ideal body position is as close to horizontal as possible

• Streamlining is similar to freestyle

• A flutter kick assists with trunk stability

Rolling Action of Trunk

• A smooth rolling action of trunk, approx. 40-45 degrees to either side, will assist in rotating shoulders

• Serves to position hand/arm for propulsion

• Serves to lift shoulder out of water and streamline trunk

Armstroke

• The pulling pattern is shaped like an ‘S’

• Slow stroke rate tend to add more dept

• Faster stroke rate has a very linear pulling

Armstroke

• Propulsive phase– Catch position– Hand enters water with

palm is facing outward• To minimize resistance• To maintain momentum

during arm recovery

Armstroke

• Propulsive phase– Lift force act as hands moves downward– Drag force takes effect – At mid-stroke may be combined with a slight

insweep due to increasing elbow bend– Hand pushes toward feet

Armstroke

• Recovery phase– Arm swings upward in an arc above shoulder– Assisted by rotation of trunk around long axis

of body