Biomechanics Of SwimmingBiomechanics Of Swimming

KickingKicking

The legs serve as stabilisers.They do this by moving away from the

midline of the body.Moment of inertia in the lower part of the

around the longitudinal axis may increase.

Natural ForcesNatural Forces

Gravity.– Works through the center of the mass

Buoyancy.– Works through the center of the volume

Due to the air in the lungs, the location of the center of volume is closer to the head than the center of the mass

Natural Forces ContNatural Forces Cont’’

Buoyancy acts upwards. Gravity acts downwards. This results in the feet of the

swimmer sinking If a swimmer swam with his feet

below his head it would increase resistance.

Therefore the kick is needed to keep the feet at water level.

ResistanceResistance

Is not only a function of frontal surface area but is also a function of body shape.

Cars?The legs can be used like a spoiler.It decreases the resistance of the swimmer

traveling through the water.This is more common in the six beat rather

than the two beat kick

Kicking PropulsionKicking Propulsion

Feet can also be used for propulsion

Example: kicking with a kick board

The effectiveness of individuals kick vary considerable

Swimmers should develop a propulsive kick rather than just to reduce resistance.

A common fault is kicking from the knee rather than the hip.

Shoulder RollShoulder Roll

Is an important technique to master.Is used to enable the arms to recover.To permit an easy breathing pattern.If shoulder roll is reduced, the body makes

jerky movements.

BreathingBreathing

A symmetrical breathing pattern has proved useful in competitive swimmers.

Many swimmers breath every one and a half strokes.

Results in swimmer breathing on both sides.

Swimming SpeedSwimming Speed

Is a product of stroke length and stroke frequency.

Stroke length. Is the distance the swimmer travels from right-hand

entry to next right-hand entry.

Stroke frequency. Is the number of the previously defined stroke

lengths completed in a minute.

Resistive forcesResistive forces

Are considerable in swimming and occur as a consequence of moving through water.

It does not increase proportionally to velocity but velocity squared.

Therefore it is economical to swim at a constant velocity.

Slipstreaming.

Resistive Forces (Drag)Resistive Forces (Drag)

There are three types of drag– Form– Surface – Wave

Form DragForm Drag

Is the cross-section area of the body exposed to the oncoming flow

The shape of the body.And velocity of the flow.

Surface DragSurface Drag

The body’s surface area.The smoothness of the body’s surface.Relative velocity of oncoming flow.A swimmer operates at the interface

between two fluids-air and water.

Wave DragWave Drag

The kinetic energy of the swimmer is transformed into waves and this process of transformation acts to reduce motion.

Greatest Resistive ForceGreatest Resistive Force

1. Form Drag

2. Wave Drag

3. Surface Drag

Reducing DragReducing Drag

Form Drag– Good streamlining of hand on entry– Good streamlining of body– Maintaining head alignment with horizontal axis– Utilizing good shoulder roll– Using legs like spoilers– Kicking to raise level of legs and body, wetsuits

can also aid in this.

Reducing Drag ContReducing Drag Cont’’

Surface Drag– Is affected by the swim suit worn– It is better to wear friction-reducing swimwear– Also shaving down exposed sections of skin

and wear swim caps

Reducing Drag ContReducing Drag Cont’’

Wave Drag– Actions such as raising and lowering head as

well as crashing arms down cause wave drag– These should be avoided– Example of the effect of wave drag

1956 Japanese breaststroker swam the entire 1st length underwater. Reducing the wave drag.