applied biomechanics

• Kinetic chain:

  ·      Open chain= most distal segment in movement is free (throwing, kicking, striking)

  ·      Closed chain= distal segment is fixed (squat, push up).
• Vf depends on: order/contribution of segments
• Summation of forces:

  ·      sum of segmental force production (typically gross to fine muscle sequence).

  ·      Sequential segment begins at peak of previous segment.
• push like movement:

  ·      greater force/accuracy

  ·      Simultaneous joint angles changes = result in straight path of distal segment.

  ·      Segments behind object to increase speed.

  Throw like patterns:

  ·      greater movement velocity with less accuracy/force.

  ·      Large muscles (high velocity) moving to proximal segments

  ·      Goal= high velocity at distal segment.

   
• Factors effecting open chain movements:

  ·      Number of rotating segments.

  ·      Angular velocities of segments.

  ·      Elastic recoil of distal tendons.

  ·      (greater velocity of sgements= greater elastic recoil).

  less skilled movement patterns= push like

  elite = throw like.
• Signs of movement faults:

  ·      Distal segments not allowed to lag to allow whipping action.

  ·      Fusion of segments (stiff joints).

  ·      Segment not fully utilised (such as lack of driving, rotation stepping forward).
• throw classification:

  ·      Overarm, sidearm, underarm throw. 

  ·      Shoulder= perpendicular to trunk.
• Sex:

  • Boys topically can throw further (during all ages).
  • Abduction angle in females at ball release is larger than males.
  • Females upper arm tends to stay more in front (unskilled pattern).
• Throwing mechanics:

  Preparation:

  ·      Backward movement of the ball with respect to the body.

  ·      Elastic energy- preload.

  ·      Displacement.

  ·      Extra segments.

   
• Throwing mechanics:

  Follow through:

  ·      Fast ball= greater forward pronation.

  ·      Curve ball= keeps force on side of ball.
• Throwing differences for speed vs accuracy:

  ·      For speed of movement= transfer of momentum from gross muscle > fine.

  ·      Accuracy=transfer of momentum of muscles at same time
• Separation angle::

  Twisting of shoulders relative to hips
• Correlates with velocity during foreword swing:

  Elbow extension= negative correlation.

  • Straighter arm= slow movement at release
• preparation: Unweighting approach (in tennis).

  1.     acceleration down (decrease GRF).

  2.     acceleration up: force to drive from ground due to storage of energy in tendons.
• hitting preparation:

  forward swing prior to contact with ball:

  ·      Great effort from internal rotators to stop external rotation.

  ·      Joint power.
• Hitting mechanics:

  Preparation: backswing:

  Straight:

  ·      Used by more immature/un-skilled.

  ·      Racket head low/down,

  ·      more time for contact phase, helps create topspin.

  Looped- used by more skilled.

  ·      large displacement and separation angle.

  ·      Ability to store elastic energy .
• hitting mechanics

  Forward swing:

  ·      accuracy over speed (such as squash)=Lower elbow extension.

  Double handed shots:

  ·      typically have greater control.

  ·      Velocity is decreased as ROM is decreased.

  ·      Ideal for children who lack strength- provide force couples.
• kicking mechanics:

  Forward swing: smaller margin of error.

  ·      Flatten arc of swing- increase likelihood/chances of making good contact in desired part o ball.

  ·      Curved arch= reduced chance or application of force.

   
• Kicking mechanics:

  Impact:

  ·      Time period of contact with ball- short= poor flexibility to apply mechanical principles.

  ·     Time period of contact with ball- long=more effectively apply mechanical work to change spin, direction.
• Spin:

  ·      Eccentric force at contact.

  ·      Bernoulli’s principle (high/low pressure differentials around air)/magnus effect.
• Kicking mechanics:

  Impact: velocity and mass:

  ·      faster foot velocity= greater foot velocity.

  ·      Effective mass= not only is mass of foot behind ball, but muscles around ankle/ upper limb to transfer greater force onto ball.
• Kicking mechanics:

  Follow through: mechanical considerations.

  ·      Permits max velocity at impact.

  ·      Dissipates force- assist in getting into a recovery position before performing skill again.