Transcript The position our body is in affects balance and stability, which result

Biomechanics
Study of Human Movement
The position our body is in
affects balance and stability,
which result in improved
performance
Centre of Gravity
Centre of gravity
can be defined as “the
point at which all
parts of the body are
equally balanced”.
Because the centre
of mass is the point
of an object where all
parts are evenly
balanced, it changes
depending upon what
position the body is in.
Centre of gravity can lie inside /
outside the body
CoG lies around the navel in neutral
upright position with arms at side
CoG shifts higher if arms are raised
CoG can lie outside the body: E.g. in
dive roll / tuck, pike, fosbury flop
Line of Gravity
Line of gravity is the vertical line that
passes through the centre of gravity to the
ground.
The line of gravity is important when
determining stability:
If the line of gravity falls within the
object/person’s base of support the
object is relatively stable.
If the line of gravity falls outside the
object/person’s base of support….
Base of Support
Base of support is the
area within an object or
person’s point of contact
with the ground.
The larger / wider the base
of support = more stable
Narrow base of support =
less stable
Line of gravity and base of
support and physical activity
Line of gravity
Top of body
moves towards
line of gravity
Direction of
movement
Leg pushes against
ground
Base of support
Stability
Stability is vital for all movements.
Improved stability often allows skills
to be executed more effectively.
Stability can be improved through
increasing abdominal strength. This
improves body control and speed as
a person is able to move their centre
of gravity in a direction more
effectively.
Stability is improved through:
Widening the
base of support
Stability is
improved through:
Lowering the
centre of
gravity
Stability is improved through:
Keeping the line of gravity within
the base of support
Stability and skill performance
Players that can make
themselves more
stable or control their
instability are able to
apply more force and
can complete skills
more successfully.
Levers
The amount of leverage a person possesses is
dependent on the length of their body, in
particular the length of their arms and legs.
Longer levers result in greater speed at the end
of the lever arms – this is beneficial for throwing
and striking objects.
Short levers can be moved with less force and
at greater speeds – this is beneficial for moving
body parts quickly and applying strength for
pushing, pulling and lifting objects.
Levers in the human body can be
manipulated to improve speed and
apply large forces at the same time
Kicking Ball
1. Leg is bent allowing the leg to
move faster
2. Leg straightens, to allow
maximum velocity and force to be
applied to the ball.
Running speed and length of levers
1. Discuss the relative merits of long
and short levers in a sprinter AND
2. How a sprinter manipulates the
length of levers to maximise force.
When raising the leg off the ground, a sprinter
bends the leg by flexing the knee, creating a
short lever which allows them to quickly move
the leg into a tuck position underneath the hips.
The knee is then extended outwards, so a large
stride can be taken, allowing the sprinter to cover
a large amount of horizontal distance before the
leg presses against the ground carrying them
forward. A long lever – when their leg pushes off
the ground – allows a large amount of force to be
imparted into the ground, allowing the sprinter to
move forward with greater speed.
“Short people are stronger than
tall people”
Identify two arguments in support of
(pro) and against (con) this
statement.
Much of this comes down to what
strength is – how short levers and
long levers can be used to generate
force for human movement.
Short people have shorter levers because their
body segments (e.g. upper arms) are a shorter
length, therefore they can apply more force with
those levers – wrestlers and power lifters are
typically short and have well-built physiques. Tall
people could be stronger than short people when
applying force at high speeds (such as swinging a
tennis racquet at a ball) – the end of their levers
(such as their arms) is travelling at a greater
momentum and can therefore impart more speed
into the object being propelled.
Enjoy your Sport!