Biomechanics And Sports | Chapter 8 Notes

Biomechanics in Sports


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. 

biomechanics and sports

Newton’s Law of Motion

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

biomechanics and sports

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.

Types of Levers and Their Applications in Sports

Types of Levers

First-class lever:

Fulcrum positioned between the effort and the load.

Examples in sports: See-saw in gymnastics, overhead barbell press in weightlifting.

Second-class lever:

Load positioned between the effort and the fulcrum.

Examples in sports: Calf raises in fitness training, pushing off the starting blocks in track and field.

Third-class lever:

Effort positioned between the fulcrum and the load.

Examples in sports: Bicep curls in weightlifting, rowing strokes in rowing sports.

Applications in Sports

First-class levers:

  • In gymnastics, the use of a see-saw as a training aid helps athletes develop balance and coordination.
  • Weightlifters use a first-class lever motion for overhead barbell presses, targeting various muscle groups.

Second-class levers:

  • Fitness training often includes calf raises to strengthen the calf muscles and improve jumping abilities.
  • Athletes in track and field utilize a second-class lever action when pushing off the starting blocks for explosive starts.

Third-class levers:

  • Weightlifters engage in bicep curls to build strength and muscular endurance in the biceps.
  • Rowing sports depend on a third-class lever motion during rowing strokes, enhancing the pulling power.

Understanding the different types of levers and their applications in sports can help athletes and coaches optimize their training techniques and improve athletic performance.


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.

4. 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 bodyweight so that balance is maintained. We do this by leaning in the opposite direction when carrying heavy weights or equipment.

4. Ensure that the center of gravity is over the 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.

5. Stability improves when we lower the center 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.

8. An opponent can be forced to lose balance if 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 position, 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. 

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.

Biomechanics in sports

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 put, 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. 

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Types Of Movements

biomechanics and sports
Biomechanics and Sports mcq various movements


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.


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 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. 


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.

Biomechanics in sports chapter 8 CBSE, class 12 Physical Education notes. This CBSE Physical Education class 12 note has a brief explanation of every topic that the NCERT  syllabus has.

You will also get ncert solutions, CBSE class 12 Physical Education sample paper, and CBSE Physical Education class 12 previous year paper.

Frequently Asked Questions

Multiple Choice Questions

  1. The Law of inertia is

a. First Law of motion

b. Second Law of motion

c. Third law of motion

2. A volleyball player hitting the ball hard for a smash, is an example of

a. First Law of motion

b. The second law of motion

c. Third law of motion

3. Which is not a type of movement

a. Flexion

b. Adduction

c. Contraindication

d. Abduction

4. Moving an art away from the midline is

a. Flexion

b. Extension

c. Abduction

d. Adduction

5. Second Law of motion is

a. Law of inertia

b. Law of acceleration

c. Law of gravity

d. Law of action-reaction

Final Words

From the above article, you must have learned about ncert CBSE class 12 Physical Education notes of chapter 8 Biomechanics in sports. We hope that these crisp and latest Physical Education class 12 notes will definitely help you in your exam.

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