2. • Biomechanics is the study of the structure and
function of biological systems by means of the
methods of mechanics (the branch of physics
involving analysis of the actions of forces).
• Biomechanics in sport incorporates detailed analysis
of sport movements in order to minimize the risk of
injury and improve sports performance.
3. • Sports biomechanics can simply be described as the
physics of sports.
• In this subfield of biomechanics the laws of
mechanics are applied in order to gain a greater
understanding of athletic performance through
mathematical modeling, computer simulation and
4. • Mechanics is a branch of physics that is concerned with the
description of motion/movement and how forces create
Within mechanics there are two sub-fields of study:
• statics, which is the study
of systems that are in a
state of constant motion
either at rest (with no
motion) or moving with a
• dynamics, which is the study
of systems in motion in which
acceleration is present, which
5. • kinematics the study of the motion of bodies with
respect to time, displacement, velocity, and speed of
movement either in a straight line or in a rotary
• kinetics the study of the forces associated with
motion, including forces causing motion and forces
resulting from motion.
Generally the primary goals of sports biomechanics are:
• Improve athletic performance by identifying and applying optimal
• Prevent injury and speed up recovery.
• optimal technique for enhancing sports performance
• The assessment of muscular recruitment and loading
• The analysis of sport and exercise equipment e.g., shoes, surfaces
• Biomechanics is utilized to attempt to either enhance performance
or reduce the injury risk in the sport and exercise tasks examined.
7. Principles of Biomechanics
1. Forces and Torques
• A force is simply a push or pull and it changes the motion of a body
• Motion is created and modified by the actions of forces (mostly
muscle forces, but also by external forces from the
environment). When force rotates a body segment, this effect is
called a torque or moment of force.
• Example - Muscles create a torque to rotate the body segments in
all tennis strokes. In the service action internal rotation of the upper
arm, so important to the power of the serve, is the result of an
internal rotation torque at the shoulder joint caused by muscle
actions. To rotate a segment with more power a player would
generally apply more muscle force.
8. 2. Newton’s Laws of Motion
Law of Inertia - Newton’s First Law of inertia states that
objects tend to resist changes in their state of motion. An
object in motion will tend to stay in motion and an object at
rest will tend to stay at rest unless acted upon by a force.
Example - The body of a player quickly sprinting down the field
will tend to want to retain that motion unless muscular forces
can overcome this inertia or a skater gliding on ice will
continue gliding with the same speed and in the same
direction, barring the action of an external force.
10. Law of Acceleration - Newton’s Second Law precisely explains how
much motion a force creates.
The acceleration (tendency of an object to change speed or direction)
an object experiences is proportional to the size of the force and
inversely proportional to the object’s mass (F = ma).
Example - When a ball is thrown, kicked, or struck with an implement,
it tends to travel in the direction of the line of action of the applied
Similarly, the greater the amount of force applied, the greater the
speed the ball has.
If a player improves leg strength through training while maintaining
the same body mass, they will have an increased ability to accelerate
the body using the legs, resulting in better agility and speed.
12. • Law of Reaction - The Third Law states that for every action
(force) there is an equal and opposite reaction force. This
means that forces do not act alone, but occur in equal and
opposite pairs between interacting bodies.
• Example - The force created by the legs “pushing” against the
ground results in ground reaction forces in which the ground
“pushes back” and allows the player to move across the court
(As the Earth is much more massive than the player, the player
accelerates and moves rapidly, while the Earth does not really
accelerate or move at all).
• This action-reaction also occurs at impact with the ball as the
force applied to the ball is matched with an equal and opposite
force applied to the racket/body.
14. 3. Momentum
• Newton’ Second Law is also related to the variable momentum,
which is the product of an object’s velocity and mass.
• Momentum is a commonly used term in sports. A team that has the
momentum is on the move and is going to take some effort to stop.
A team that has a lot of momentum is really on the move and is
going to be hard to stop.
• Momentum is a physics term; it refers to the quantity of motion that
an object has. A sports team that is on the move has the momentum.
If an object is in motion (on the move) then it has momentum.
p = m • v
where m is the mass and v is the velocity.
15. Linear Momentum
• Linear momentum is momentum in a straight line e.g. linear momentum is
created as the athlete sprints in a straight line down the 100m straight on
• Angular momentum is rotational momentum and is created by the rotations
of the various body segments e.g. The open stance forehand uses
significant angular momentum. In tennis, the angular momentum
developed by the coordinated action of body segments transfers to the
linear momentum of the racquet at impact.
16. 4. Centre of Gravity
• The Center of Gravity (COG) is an imaginary point around which
body weight is evenly distributed.
• The center of gravity of the human body can change considerably
because the segments of the body can move their masses with joint
• This line of gravity is important to understand and visualise when
determining a person's ability to successfully maintain balance.
• When the line of gravity falls outside the Base of Support (BOS),
then a reaction is needed in order to stay balanced.
17. The center of gravity
can be located
within or outside
the body depending
on the body's
position; it is inside
an object when the
object is uniform
and outside the
object when it is not
19. 5. Balance
• Balance is the ability of a player to control their
equilibrium or stability. You need to have a good
understanding of both static and dynamic balance:
• The ability to control the body while the body is
stationary. It is the ability to maintain the body in
some fixed posture. Static balance is the ability to
maintain postural stability and orientation with
center of mass over the base of support and body at
• The ability to control the body during
motion. Defining dynamic postural stability is more
challenging, Dynamic balance is the ability to
transfer the vertical projection of the center of
gravity around the supporting base of support.
21. 6. Friction
• Friction can be defined as the resistance
to motion of two moving objects or
surfaces that touch. When both the
surfaces are smooth, the force of friction
reduces to almost zero.
Three types of friction are
(i) Static Friction is a force that keeps an
object at rest. It must be overcome to
start moving the object. If a small
amount of force is applied to an object,
the static friction has an equal
magnitude in the opposite direction.
(ii) Kinetic Friction is a force that acts
between moving surfaces. An object
that is being moved over a surface will
experience a force in the opposite
direction as its movement.
22. 7. Axes & Plane
Plane is an imaginary, flat surface passing
through the body organ or plane is the
surface on which the movement occurs.
There are following types of planes:
a) Sagittal or Medial plane: dividing the
body into left and right halves. It is also
known as anteroposterior plane. Most of
the sports and exercise movements that
are two dimensional, such as running,
long jumping and somersault take place in
b) Frontal or Coronal plane: passes from
left to right dividing the body into
posterior to anterior halves (front and
c) Transverse or Horizontal plane: divides
the body into top and bottom halves.
23. An axis is a straight line around which an
• Movements at the joints of human
muscoskeletal system are mainly
rotational and take place about a line
perpendicular to the plane in which they
occur. This line is known as axis of
There are following types of axes of rotation:
a) Sagittal axis: The sagittal axis passes
horizontally from posterior to anterior. It is
formed by the intersection of the sagittal
and transverse plane. Sagittal axis passes
from front to back.
b) Frontal axis: The frontal axis passes
horizontally from left to right. It is formed
by the intersection of frontal and
horizontal plane. Frontal axis passes from
side to side.
c) Vertical axis: The vertical axis passes
vertically from inferior to superior. It
passes straight through the top of the head
down between feet. It is formed by the
intersection of sagittal and frontal plane. It
is also known as longitudinal axis.
24. Types of movements
There are various types of movement in body parts which can be divided in four types
i.e. gliding & angular movements, circumduction & rotation and few other
1. Gliding movements: Gliding movements is the simplest kind of movement that
can take place in a joint, one surface gliding or moving over another without any
angular or rotator movement.
25. 2. Angular movement: are produced when the angle between the
bones of a joint changes.By angular movement the angle between
the two bones increased or decreased. The various movements
which fall under angular movements are described below:
a) Flexion: Bending parts at a joint so that the angle between them
decreases and parts come closer together (bending the lower limb at
b) Extensions: Straightening parts so that the angle between them
increases and parts moves farther apart (straightening the lower
limb at the knee).
c) Abduction means moving a part away from the midline (lifting the
upper limb horizontally to form a right angle with the side of the
d) Adduction means moving a part towards the midline ( returning
the upper limb from the horizontal position to the side of the body).
29. Running Biomechanics
Running is similar to walking in terms of locomotors activity.
• Greater balance
• Greater muscle strength
• Greater joint range of movement
31. Major muscles involved in running
The major muscles involved in running are described below:
• Glutes: these muscles stabilize your hips and legs. These muscles
work with hamstring muscles and help in hip flexors.
• Quads: Quads propel you forward and help straighten out the leg in
front so that it can make a good contact with the surface of ground.
• Calves: these muscles give you spring in your step and at the same
time these muscles act as shock absorbers.
• Hamstrings: As you move forward, the action switches to your
hamstrings, the muscles at the back of your thigh muscles. These
muscles helps you in pulling the leg back behind and give you
strength to propel your body forward.
• Core muscles: Strong abs and back are really important because
they keep yours posture upright and overall form good. These
muscles play a significant role in running.
• Biceps: biceps also play a vital role in running. Biceps maintain a
bent arm and help in swinging your arms back and forth while
34. Gait Analysis
• Study of human
• Walking and running
• Walking is a series of
– A single gait cycle is
known as a STRIDE
35. Stance Phase of Gait
• When the foot is contact with the ground only
• Propulsion phase
• Stance phase has 5 parts:
– Initial Contact (Heel Strike)(1)
– Loading Response (Foot Flat)(2)
– Midstance (2)
– Terminal Stance (3)
– Toe Off (Pre-Swing) (4)
Notes de l'éditeur
Sport and exercise biomechanics encompasses the area of science concerned with the analysis of the mechanics of human movement.
Sports biomechanics is a quantitative based study and analysis of professional athletes and sports activities in general.
This concept is critical to understanding balance and stability and how gravity affects sport techniques.
The direction of the force of gravity through the body is downward, towards the center of the earth and through the COG.
Dynamic balance is the ability to maintain postural stability and orientation with center of mass over the base of support while the body parts are in motion