BioMechanics

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Bio-Mechanics

• USA Track FieldLevel 1
• Coaching School

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Objectives

• To develop a basic understanding of fundamental
  physics, principles as they apply to the human
  body in athletic performance. (The application of
  Newtons Three Laws of Motion to Track and Field)
• To improve the coaches background in the sport
  science of bio-mechanics
• To improve the line of communication between the
  coaches and the athletes
• To improve the athletes performance

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Definition

• Biomechanics is the study of physics applied to
  human movement.

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Newtons Three Laws of Motion

• Law of Inertia
• Law of Acceleration
• Law of Action/Reaction

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Law of InertiaNewtons 1st Law

• A body will stay in a state of rest or constant
  velocity unless acted upon by an external force
  that changes that state. (i.e. gravity, wind,
  friction with the ground or moving into some
  objects way,)

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Law of AccelerationNewtons 2nd Law

• force applied to a body causes an acceleration of
  that body of a magnitude proportional to the
  force, in the direction of the force, and
  inversely proportional to the bodys mass

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Law of Action/ReactionNewtons 3rd Law

• for each and every action, there is an equal and
  simultaneous reaction

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Concepts Necessary to Understanding Newtons Laws
of Motion

• Kinematics-describe motion
• Linear Motion
• Rotary Motion
• Velocity
• Speed
• Acceleration
• Deceleration
• Kinetics
• Force
• Center of Gravity or Center of Mass
• Inertia
• Impulse

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Linear Motion

• motion along a generally straight line
• such as the path of a long jumper during the
  approach run

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Rotary Motion

• motion which is turning or rotating around an
  axis, such as the the turning of a thrower before
  the throw

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Velocity

• the distance a body travels in a specific
  direction divided by time (Vd/t).

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Speed

• Distance traveled, divided by time.
• 100m / 10 seconds 10m/sec

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Acceleration

• a positive rate of change of velocity (speeding
  up)

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Deceleration

• a negative rate of change of velocity (slowing
  down)

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Force

• Force is a push or a pull
• any physical cause that modifies the motion of a
  body
• putter against the shot
• jumper against the ground

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Center of Gravity (COG)or Center of Mass (COM)

• the point where the bodys mass is considered to
  be concentrated.
• It is not a fixed point in the human body.

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Inertia

• The resistance that an object or body has to
  change its state of movement or position or rest.
• Newtons 1st Law

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Impulse/Momentum

• Force x time
• change in velocity is dependent upon the force
  itself and upon the time during which the force
  is applied
• an increase in the force or in the time of the
  force will increase the impulse

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Trajectory

• The path of a projectile it can be a parabolic
  curve or it can be an aerodynamic curve

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Parabolic Curve

• the regular flight curve followed by the COG when
  projected in air.
• the curve can not altered by movement in the air.

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Acceleration due to Gravity

• the acceleration of a freely falling body, with
  an increasing velocity of approximately 32 feet
  per second every second that it falls.

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Torque

• A turning force. The amount of force applied to
  an object away from its center of gravity results
  in a rotary motion.

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Work

• When a force is applied to a mass sufficient to
  move some distance.

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Power

• The amount of work done in a period of time.
• Power Force x Velocity

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Circular Motion

• Rotation of a body outside the point of rotation.

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Centripetal Force

• center seeking force

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Axis

• straight line about which a body, either animate
  or inanimate, rotates

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Radius of Rotation

• for a constant turning speed, the greater the
  radius of rotation can be, the greater the linear
  velocity of the most distant part. The discus
  should be kept as far away from body as possible
  and the arm should be at a right angle to the
  body.

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Moment of Inertia

• the closer the mass to the axis, the less the
  resistance is to speeding up rotation. The arm of
  the metronome oscillates more rapidly as its
  weight is moved closer to the axis of rotation.

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Conservation of Rotary Momentum

• when the radius of a rotating body (or limb) is
  increased the rotational velocity decreases, when
  the radius decreases the rotational velocity
  increases.

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Stretch Reflex

• a stronger concentric muscle contraction can be
  obtained when it is directly proceeded by a
  previous eccentric contraction. By braking a
  motion opposite to the intended action, the
  stretched muscle will now contract more
  forcefully.

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Body Separation

• in the power position of the throwing events the
  hips open first or lead while the shoulders are
  still semi-closed and trailing. It is more
  obvious in the discus and hammer where the mass
  of the implement and the radius of rotation slow
  the upper body and keep it trailing the lower
  body throughout the turn. This creates a stretch
  reflex.

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Acceleration of a Limb

• acceleration in one direction creates a force in
  the opposite direction. The fast acceleration of
  the limbs at the beginning of take-off increases
  ground reaction force.

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Deceleration of a Limb

• deceleration in one direction creates a force in
  that direction. The sudden deceleration of the
  limbs unweights the take off leg to facilitate
  its fast extension. (Also thought of as
  Transference of Momentum)

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Transference of Momentum

• process through which momentum may be transferred
  from the entire body to one part, as in discus
  throwing.

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Checking Linear Motion or Hinged Moment

• when the linear motion of an object is
  interrupted at one end of the object, the other
  end continues ahead at an increased speed

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General Principles of Force Application

• Force should be applied in the proper direction
• Apply force over the greatest range of motion
• Proper Body Position
• Slow to Fast Rhythm
• Summation of Forces