🎾 Itf - Level - 2 - Introduction - Cơ Sinh Học¶
Giới Thiệu¶
Itf - Level - 2 - Introduction - Cơ Sinh Học — tài liệu 47 trang từ thư viện sách tennis.
Chủ đề chính: Biomechanic, Cơ sinh học, Coach, Power
Tóm tắt nội dung (trích từ tài liệu gốc): ITF Coaches Education Programme Level 2 Coaching Course Biomechanics of tennis: An introduction Coach Education Series Copyright � ITF 2007 By the end of this session you should be able to: � Understand optimum technique through a practical knowledge of biomechanics � Improve technical diagnosis and correction � Understand how power is generated in strokes � Understand how control is achieved in tennis � Increase knowledge of the technical characteristics of the modern game Coach Education Series Copyright � ITF 2007 Biomechanics: Definitions The study of human motion The study of the internal
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ITF Coaches
Education Programme
Level 2 Coaching Course
Biomechanics of
tennis: An
introduction
Coach Education Series Copyright � ITF 2007
By the end of this session
you should be able to:
� Understand optimum technique through a
practical knowledge of biomechanics
� Improve technical diagnosis and correction
� Understand how power is generated in
strokes
� Understand how control is achieved in tennis
� Increase knowledge of the technical
characteristics of the modern game
Coach Education Series Copyright � ITF 2007
Biomechanics:
Definitions
The study of human motion
The study of the internal (muscular, bone
and joint) and external (wind, gravity,
pressure) forces affecting human
performance
Coach Education Series Copyright � ITF 2007
Biomechanics:
Areas that involves
� Efficiency and effectiveness of movement
� Sports medicine implications of
performance
� Effects of equipment design on
performance and the performer
Coach Education Series Copyright � ITF 2007
What is optimum
technique?
Optimum technique incorporates the most
efficient combination of power and
control in both stroke and movement
technique whilst minimising the risk of
injury
Coach Education Series Copyright � ITF 2007
Elements of technique
Efficiency � Economy: less energy
Effectiveness � Result: OK
Safety - Injury free
Coach Education Series Copyright � ITF 2007
Benefits of technique
POWER CONTROL
NO INJURIES
Coach Education Series Copyright � ITF 2007
BIOMECHANICS
TECHNIQUE
STYLE
Coach Education Series Copyright � ITF 2007
BIOMECHANICS Laws, principles
TECHNIQUE Practical application
STYLE Individual understanding
Coach Education Series Copyright � ITF 2007
STYLE
� Personal interpretation and application
of the biomechanics and the technique
Coach Education Series Copyright � ITF 2007
Main biomechanical
principles for tennis
�B Balance
�I Inertia
�O Opposite force
�M Momentum
�E Elastic Energy
�C Co-ordination chain
Coach Education Series Copyright � ITF 2007
Teaching technique
TRADITIONAL MODERN
� Grip �B
� Stroke �I
� Backswing �O
� Contact point �M
� Follow through �E
� Recovery �C
� Footwork
Coach Education Series Copyright � ITF 2007
What's balance?
� The ability to maintain equilibrium (a state of
readiness) either dynamically or statically
� Tennis requires dynamic balance
� It is controlled by the position of the centre of
gravity
� It directly relates to vision
� It is controlled by the semi-circular canals in
the ear
Coach Education Series Copyright � ITF 2007
Factors affecting stability
� Size of the base of support
� Height of the centre of gravity
� Distance of the line of the centre of
gravity from the edge of the base of
support
� Mass of the body
Coach Education Series Copyright � ITF 2007
Important aspects of
stability
� Base of support
� Height of centre of gravity
� Position of head over the shoulders
� Arms: Use as orchestra conductor
Coach Education Series Copyright � ITF 2007
Inertia
� Law: The body will stay at rest or motion
until acted upon by an outside force
� It is the resistance of a body to move or
to stop moving
Coach Education Series Copyright � ITF 2007
Inertia (II)
� When in ready position: Body has
"resting inertia"
� To move the player needs to overcome
the resting inertia by using force
(muscular contraction) or gravity
Coach Education Series Copyright � ITF 2007
Inertia (III)
� When hitting:
� Bent arm:
� Smaller moment of inertia
� Less resistance to rotation
� More racket speed
� Straight arm:
� Bigger moment of inertia
� More resistance to rotation
� Less racket speed
Coach Education Series Copyright � ITF 2007
Inertia (IV)
� Mini-tennis:
� Kids move the racket faster if it is a racket
with a shorter throat
� When running for a passing-shot:
� Overcome resting inertia by using gravity
and by creating sufficient force against the
ground to move
Coach Education Series Copyright � ITF 2007
Opposite force
� For every action, there is an equal and
opposite reaction
� Stroke and movement are initiated from
the legs by pushing against the ground
� The ground pushes the player back up
with the same amount of force
Coach Education Series Copyright � ITF 2007
Examples of opposite force
� Tossing arm in the serve goes down
� Knee bent in the serve
� Non-playing arm in one handed
backhand
� Right leg at the end of the serve
� Left leg in the follow through of 2
handed BH
Coach Education Series Copyright � ITF 2007
Momentum
� The force generated by a body
� It is the body's quantity of motion
� It is the amount of mass of the body
related to its speed (mass x velocity)
� The mass remains the same for the
match, so the greater the velocity, the
greater it's momentum
Coach Education Series Copyright � ITF 2007
Types of momentum
� Linear: Momentum in straight line
i.e. "Step into the shot", down the line
shots, slice shots
� Angular: Momentum in a circular motion
i.e. "Rotate hips and trunk", cross court
shots, topspin shots
Coach Education Series Copyright � ITF 2007
Types of momentum
� Both linear and angular occur at the
same time
Coach Education Series Copyright � ITF 2007
Other type of momentum
� Vertical momentum:
� In the serve
� In the smash
� Example of 3 momentums: the serve
Coach Education Series Copyright � ITF 2007
Elastic energy
� Energy stored in the muscle as a result
of stretching the muscle
� If a player bends the knees and
immediately jumps up, he will create
more elastic energy than if he remains
with the knees bent for about 2 seconds
and then jumps up
Coach Education Series Copyright � ITF 2007
Elastic energy
� There should not be too long a pause
between take back and follow through
� Coaches should encourage a
continuous flowing motion for all strokes
� Examples:
� Split step
� Pre-stretch in take back
Coach Education Series Copyright � ITF 2007
Momentum and elastic
energy
� Initiating the stroke from the legs by pushing
against the ground
� Ensure that pre-stretching of the trunk
muscles occurs by twisting the upper body
while keeping the head facing toward the on-
coming ball
� Ensure that the racket path allows the
production of momentum through a loop or
elbow lead take back on the forehand
Tennis Canada
Coach Education Series Copyright � ITF 2007
Momentum and elastic
energy
� All strokes have 2 moments from the
mechanical point of view:
� Pre-stretching
� Releasing
Coach Education Series Copyright � ITF 2007
Co-ordination chain
"...the segments of the body act as a
system of chain links whereby the force
generated by one link, or body part, is
transferred in succession to the next
link"
J. Groppel (1984)
Coach Education Series Copyright � ITF 2007