Ch6 development of ballistic skills

ballistic skills

• force is applied to an object to project it → newton’s 1st Law of Motion

throwing

• patterns/forms

  • underhand (one-or two-hand

  • sidearm

  • overarm (one- or two-hand)

characteristic of early throwing

• limited trunk rotation

  • forward-backward movement

• mostly arm action

• elbow pointed up

• throw executed by elbow extension alone

• no step → homolateral step

developmental changes in throwing arm action

upper arm action:

1. oblique

2. aligned but independent

3. lagging

forearm action:

1. no lag

2. lag

3. delayed lag

developmental changes in early throwing

• throwers DO NOT achieve same step for each body component at same time

• some step combinations are more likely

  • structural constraints limit possible combinations

• not everyone reaches the highest step in each component

  • girls and women often remain in intermediate

throwing in (older) adulthood

• older adulthood demonstrate moderately advanced steps (but qualitatively different)

  • structural (musculoskeletal) constraints likely to influence movement patterns

• decline is usually gradual

  • variability in movement patterns

• change is typically in the control rather than coordination of movements

  • slowed speed

  • decreased range of motion

throwing for force

• preparatory windup

  • weights shifts to back foot

  • trunk rotates back

  • arm swings down and around

• long step with opposite leg

• differentiated trunk rotation

• upper arm and forearm lag

• movements are sequential to transfer momentum

throwing for accuracy

• throwers may use lower developmental steps for throws requiring accuracy vs force

• when required to throw a greater distance, differences between throws are minimal

assessment

• product measures (outcome)

  • accuracy

  • distance

  • ball velocity

• process measures (movement pattern)

  • developmental sequences

  • performance criteria

sidearm striking

• arm remains at or below shoulder level

• various body parts can be used

• implements can be used

char of early striking

• chopping motion (elbow extension)

• little leg and trunk movement

proficient sidearm striking

• sideways preparatory stance and long step

• differentiated trunk rotation

• horizontal swing through large range of motion (arm extended before contact)

• sequential movements

developmental changes in striking

• trend to use of trunk rotation

  • none → blocked → differentiated

• plane of swing

  • vertical → horizontal

• grip

  • power grip → “shake-hands” grip

• elbows move away from body and extend before contact

overarm striking

• without an implement

  • e.g volleyball serve

• with an implement

  • e.g tennis serve

char of early overarm striking

• trunk rotation is limited

• swings with bent elbow

• little or no lag with swing forward

• looks like early throwing

• ball contact is low (and down)

proficient overarm striking

• lower and upper trunk are rotated (back) more than 90 degree

• elbow is held between 90 degree and 119 degree at start of forward movement

• racket lags behind arm in forward swing

• movement is sequential

developmental changes in overarm striking

• trunk, upper, and lower arm, and leg sequences similar to those for overarm throwing

• preparatory trunk action

1. no trunk rotation

2. minimal trunk rotation

3. total trunk rotation

• elbow action in ball-contact phase

1. very small or very large angle

2. intermediate angle (20 degree to 89 degrees)

3. ideal angle (90 -119)

• spinal and pelvic rom

1. rotation of less than 45

2. rotation of 45-89

3. rotation of >90

racket action

1. no racket lag

2. racket lag

3. delayed racket lag

overarm striking:older adults

Jagacinski, Greenberg, & Liao (1997)

• studied iron shot (did not require maximal force)

• older golfers reach peak force earlier in swing

• older golfers may need to exert more force than younger golfers for same shot

• most golfer were just as accurate as younger golfers

Haywood & Williams (1995)

• studied tennis “first” serves

• studied older servers at moderate levels

• two former teaching professionals were categorized at highest levels (maintained coordination of movements)

kicking

• kicker strikes ball with foot

• kicker must have perceptual abilities and eye-foot coordination to make contact

  • stationary → moving ball

characteristics of early kicking

• no step is taken with non-kicking leg

• kicking leg pushes forward

intermediate kicking

• steps forward with non-kicking leg

• bends knee in preparation, but leg swing is minimal

• limited arm or trunk movement

proficient kicking

• preparatory windup

  • trunk is rotated back

  • kicking leg cocked + knee bent

• elongated step (~leap)

• trunk rotates forward → full ROM

• movement is sequential

  • thigh rotates forward → lower leg extends

  • follow through (full ROM)

• arms move in opposition to legs

  • in response to trunk and leg motion

punting

• the ball is dropped from the hands

• punting is more difficult than kicking for children

char of early punting

• ball is tossed up rather than dropped

• punter often contacts ball with toes vs instep

proficient punting

• arms extended to drop ball before final stride

• arms then drop to sides and move into opposition to legs

• punter leaps into supporting leg, swings punting leg vigorously up to make contact

• punting leg is kept straight; toes are pointed

developmental changes in punting

ball-release phase

1. upward toss

2. late drop from chest height

3. late drop from waist height

4. early drop from chest height

ball-contact phase

1. arm drop

2. arm abduction

3. arm opposition

1. no short step, ankle flexed

2. long step, ankle extended

3. leap and hop