Biomechanics 2

Sports

Meaning

Biomechanics is the science concerned with

the analysis of the mechanics of human
movement. It explains how and why the
human body moves.
It is the study of the function and motion of
the mechanical aspects of biological systems.
Biomechanics tells us how our muscles, bones,
tendons, and ligaments work together to
produce movement.

It gives us a detailed analysis of any sports

movements, which helps to minimize the risk
of injury and improve sports performance.

Importance Of Biomechanics In
Sports
Improves sports performance: Biomechanics
tell us the right techniques for effective and
efficient results by using minimum muscular
force and getting maximum results.
Improvement in technique: Biomechanics
helps to improve new techniques, which helps
us to get more results

Helps to develop the best sports equipment:

Biomechanics helps us to make correct and
scientifically proven equipment.

Improvement in training: Coaches can give the

best training to athletes on the basis of
scientific knowledge. He can analyze the
player’s movement in a better way.

Prevents injuries: It helps us to know the

forces that can lead to the injuries during the
game situation.

Knowledge of safety principles:

Biomechanics gives the understanding to

analyze different safety movements
Helps in research work: It helps to impart
scientific teaching and learning processes.

Creates confidence in players: Players come to

know the correct techniques to execute the
movement. Thus it improves the confidence of
the player.

Newton’s
 Law of
Motion
Application In Sports

Man is said to be the man of action. So,

movements are involved everywhere. For
every moment there is motion. Therefore
everything that moves is governed by the
‘Laws of motion’.

These laws of motion were formulated by Sir

Isaac Newton in 1687. He explained and
investigated that every motion is under the
impact of following laws of motion

First Law of motion

First law is also named as Law of Inertia. This

law states that an object at rest will remain at
rest or an object in motion will remain at
motion at constant velocity unless acted upon
by an external force.

In another word, an object will remain in a

stationary position or remain in motion unless
an external force is applied to move or stop.
Application in Sports
A football placed at a penalty point will
remain at rest unless a player kicks the ball to
score a goal, Or that same football will
continue to move at a constant velocity unless
a force acts on it to slow it down (e.g. wind
resistance) or change its direction (e.g.
gravity).

Second Law of Motion

The Second Law of motion is also named the

‘Law of Acceleration’.

According to this law, the rate of change in the

velocity of an object is directly proportional to
the force applied and inversely proportional to
the mass of the body.
The greater the force applied the faster the
velocity and more displacement. If less force
is applied then the displacement and
acceleration are also less

If unequal forces are applied to objects of

equal mass the greater force will cause more
acceleration. If equal forces are applied to
objects with unequal mass, the object with
mass has less acceleration
Application in Sports

A Volleyball player pushes the ball slowly for

a drop, whereas hits the ball hard for a smash.
Thus drop is slow because there is less force
applied, whereas smash is very fast as there is
a great force applied.

In the shot put event, a player who exerts more

force and tosses the shot put at the correct
angle has greater displacement.

Third Law of Motion

This law is also known as the ‘ Law of Action

and Reaction’

This law states that for every action there is an

equal and opposite reaction.
Application in Sports

In swimming, if a swimmer pushes the water

backward, in return he is pushed forward by
the water.

When a person walks he presses the ground in

the backward direction and the ground pushes
him in the forward direction with an equal
force.

Equilibrium
Equilibrium is defined as a state of balance or
stable situation, where opposite forces cancel
each other out and where no changes are
occurring.

When a body or a system is in equilibrium

there is no net tendency to change. In
mechanics, equilibrium has to do with the
forces acting on a body.

When no force is acting to make a body move

in a line the body is in translational
equilibrium, when no force is acting to make
the body turn the body is in rotational
equilibrium. However, a state of equilibrium
does not mean that no forces act on the body
but only that the forces are balanced.
 Types of Equilibrium

1. Dynamic Equilibrium

2. Static Equilibrium

Dynamic Equilibrium: Dynamic equilibrium

is the balance of the body during movement

Static Equilibrium: It is the balance of the

body during rest or in a stationary position.

The fundamental human movement is 7 in

numbers. These basic movements that the
human body can perform are pulled, push,
squat, lunge, hinge, rotation, and gait. All
other movements are variations or
combinations of these.

Stability principles give sportsmen the rule

about being in balance while running. They
offer guidance to trainers for improving a
sports person’s ability to achieve static balance
and dynamic balance.

Guiding Principles To Determine Degree of

Equilibrium (stability)

1.Broader the base, greater the stability: For

greater stability, increase the area of the base
and lower the center of gravity as much as is
consistent with the activity involved.

This is the reason why a golfer will take a

wide stance before swinging at the golf ball or
volleyball players, while offering defense, and
spread their feet wide.

2. Lower the center of gravity, higher the

stability: For an accelerated start, we need to
keep the center of gravity as low as possible
and as near as possible to the edge of the base
nearest to the direction of intended motion.
This is the reason racers crouch at the start of
the race and the racing cars have very low
floors.
3. When the body is free in the air, if the
head and feet move down, then the hips
move up and vice versa: While performing a
high jump, this principle comes into play.

The players tend to lift up their head and thrust

one foot as high as possible. Once the head
and one leg clear the bar, they are dropped
which raises the hips to clear the bar.
As the hips are lowered, the opposite leg is
raised to clear the bar. Pole vault, diving while
competing in swimming and hurdle races are
also sports where this principle is of
paramount importance.

3. Body weight is directly proportional to

stability: The heavier the sportspersons,
the more stable they are. It is obvious that a
lighter person can be moved far more
easily than a heavier person.

This is the reason why sports like wrestling,

boxing, judo, etc., are organized according to
different weight groups.

Equilibrium (Stability) Principles

1.To maintain balance while being stationary,
the athletes must maintain their center of
gravity over the base of support. Thus, to
begin a free weightlifting movement, the lifter
needs to hold a standing position and then go
into a squat and stand again.

2.If the balance is lost, an athlete needs to

enlarge the base of support and make sure that
the center of gravity is over it. Like, by
keeping the feet wider to prevent falling after
being pushed helps recover balance.

3.While carrying any object, one needs to shift

the body weight so that balance is maintained.
We do this by leaning in the opposite direction
when carrying heavy weights or equipment.
 Ensure that the center of gravity is over the
4.

center of the base of support. Like, while

performing a handstand, the hips need to
remain towards the center of the base which is
formed by the hands.

Stability improves when we lower the center

5.

of gravity. This is the reason why during shot-

put, the follow-through involves bending the
knees.

6. The greater the friction between the

supporting surface and the athlete’s body, the
greater the ability to maintain balance. This is
the reason why sports persons wear
specialized shoes that prevent excessive
sliding on a playing surface.
7. Shifting the center of gravity towards an
approaching force increases an athlete’s ability
to maintain balance. This explains why a
football lineman shifts weight towards the
opposing line prior to the snap.

An opponent can be forced to lose balance if

8.

pushed or pulled in the direction where the

center of gravity is closest to the edge of the
base of support. Boxers use this principle to
create a loss of balance by shifting the weight
on the heels.

9.For positions of readiness, if the distance is

shorter then the center of gravity must move to
the base of support, the more rapidly the body
can be put in motion in that direction. for
example, sprinters in the “set” position shift
their weight in the direction of the race.
 Center Of Gravity

The Center of gravity is the point in a body or

system around which its mass or weight is
evenly distributed or balanced and through
which the force of gravity acts.

The center of gravity is fixed, provided the

size and shape of the body do not change.

An athlete’s center of gravity is the exact

middle of the body and can rotate freely in any
direction and where ±weight is balanced on
all opposite sides.
It exists at a point along the midline of the
body at about 55% of the athlete’s height. Core
stability enables athletes to control their body
oosiåon, generate optimum power, and transfer
force along the kinetic chain.

The human body is made up of individual

body parts with their own weight. So, our total
body weight is the sum of individual weights
of organs such as our arms, legs, etc.

The point, about which the distribution of

these individual weights is symmetrical, is the
center of gravity of the body. Thus, if a body
has more mass distributed in its upper part, the
center of gravity will be at the top of the body.
This applies to humans, as the center of
gravity of an average person is located
approximately at a height of one meter, thus
being above the waist.

There are two properties of the center of

gravity that have a great impact on sports. First
of all, its location is dependent on the shape of
the body.

So if the same body is to take a different

shape, the position of the center of gravity will
shift. An athlete that bends his/her legs will
lower his/her center of gravity position.
amongst other things, will result in greater
stability, something especially important in
sports such as wrestling.
This may sound the strangest, but the center of
gravity can lie entirely outside the body itself.
For example, if the body is hollow, it will
literally be positioned somewhere in the air.

During the 1968 Olympic Games in Mexico,

Dick Fosbury used these principles to develop
a pole vault technique now called the Fosbury
Flop.

The technique was that by clearing the bar

with his back and by changing the shape of his
body, he cleared the bar without his center of
gravity having to also clear it.
With this change in body shape, he was able to
move his center of gravity outside his body.
Also, the energy needed to execute the
maneuver is decreased as by lowering the
position of the body, less energy is required to
clear the bar.

The center of gravity moves according to the

athlete’s body position. For example, the
center of gravity of the runner is in the lower
region of the pelvis and in front of his body
because his upper body is leaning forward.
Having the center of gravity lower and in front
of his lower body is advantageous for
acceleration.

So, if the same body is to take a different

shape, the position of the center of gravity will
shift. An athlete that bends his/her legs will
lower the position of his/her center of gravity.
This, amongst other things, will result in
greater stability, something especially
important in sports such as wrestling.

Projectile In
Sports
Projectile: When an object is thrown into
space either horizontally or at an acute angle
under the action of gravity is called a
projectile. Or,

It refers to the motion of an object projected

into the air at an angle. The path followed by a
projectile is known as a trajectory.
In sport, there are many examples of
projectiles e.g. putting the shot, throwing a
hammer, discus, and javelin in athletics.

Factors affecting the projectile

trajectory

When an object is projected through space,

three forces influence the course of the flight
(i) Propelling Force:

The initial force produces certain effects

depending upon its point and direction of
application. If the application is directly
through the projectile’s center of gravity, only
linear motion results from the force.

As the object is moved further from the center

of gravity, the rotator motion of the object
increases at the expense of linear motion. If
the force is below the object’s center of
gravity, backspin is the result.

Forward spin results when the force is above

the center of gravity. When the force is off-
center to the left, clockwise spin results, and
when it is off-center to right, counterclockwise
spin occurs.

(ii) Force of Gravity:

As soon as contact is broken with a projected

object, the force of gravity begins to finish the
upward velocity of the object.

Finally, gravity overcomes the projectile’s

motion and the object begins to descend. The
factors that determine how soon gravity will
cause the object to descend are –
(a) Weight (mass) of the object
(b) Amount of force driving it upward
(c) The effect of air resistance on the object.
(iii) Effect of Air Resistance:

As the speed of an object increases, air

resistance has a greater retarding effect. The
more surface area an object presents in the
direction of movement, the greater will be the
effect of air resistance.
(iv) Angle of Release:

The angle between the initial trajectory and the

horizontal determines the shape of the
parabola described in flight by the object or
body. The optimum angle for the maximum
horizontal distance of flight is 45°.

The steepness or shallowness of the curve will

depend on the angle of projection, with angles
greater than 45° producing steeper curves and
angles less than 45° producing shale-lower
curves.

(v) Height of Release:

The next factor that affects the trajectory of a

projectile in sport is the height of the point of
projection or release in relation to the landing
surface of the object or body.
There are examples from sports where the
height of the projection is both above and
below the landing surface. For example, in the
shot putt, the optimum angle is less than 45°
because the point of release is well above the
land surface

Friction &
 Sports
Friction is a force resisting the relative motion
of solid surfaces, fluid layers, and material
elements sliding against each other. It
generally creates an obstruction to moving
objects.

It is created whenever two surfaces move or

try to move across each other. It opposes the
motion of one surface across another surface.

Friction depends on the texture of both

surfaces and on the amount of contact force
pushing the two surfaces together.
 Types of Friction

There are two types of friction

Static Friction: It occurs when a body is
forced to move along a surface but movement
does not start. This friction is present between
two or more solid objects that are not moving
relative to each other.

Without static friction, your feet would sleep

out and it makes it difficult to walk.

Dynamic/kinetic friction: It occurs when two

objects are moving relative to each other and
work together. Further, it is of two types

Sliding Friction: It is a kind of friction that

acts on the object when it slides or rubs over
the surface. It is weaker than static friction.
Sliding friction causes wear and tear

Rolling friction: It is a force that slows

down the motion of a rolling object. It acts on
objects when they are rolling over a surface.

Advantages of friction

It helps to move: Frictional force helps to

move the object, e.g. running, or walking with
the friction of feet and surface.

Stop the moving object: It helps to stop the

moving object through friction
Hold or grip object: With the help of friction,
our fingers and palm enable us to grasp and
hold objects.

Keep the objects at their position: Friction

can hold the object at its position.

Disadvantages of friction

Makes movement difficult: Friction can

make the movement difficult. For example,
excess friction can make a box difficult to
slide on the floor.

Waste of energy: Excess friction means extra

energy, so extra energy is wasted because of
friction.

Types Of
Movements
 Flexion

It describes a bending movement that

decreases the angle between two body parts,
that is bones of the limb at a joint. Flexion
refers to movement in the anterior direction.
It happens when muscles contract and move
your bones and joints

Example: Elbow flexion is decreasing the

angle between the radius and the humerus.
Knee flexion is decreasing the angle between
the femur and tibia.

Flexion of the shoulder or hips refers to the

movement of the arm or leg forward.

Extension

It is the opposite of flexion, it is a movement

that increases the angle between two body
parts.
Extension refers to movement in the posterior
direction.

Extension at the elbow is to increase the angle

between the ulna and the humerus. Extension
of the knee is to increase the angle between the
tibia and the femur.

Abduction

Abduction is a movement that pulls a structure

or part away from the midline of the body. The
muscles which create this type of motion is
known as an abductor.

Abduction of the wrist is also known as radial

deviation.

Swinging the arms laterally from the side of

the body up to the shoulder or moving the legs
away from the midline is abduction are some
examples.

Adduction

It refers to the movement that pulls apart

towards the midline. When the arms straight
out at the shoulders bring down to their sides
is adduction.

Arms closing towards the chest, bringing the

knees together, bringing all the fingers or toes
together, and thumb back to the normal
position are some of the examples of
adduction.