Chapter 6- Development of Ballistic Skills / Motor Development & Learning

Ballistic Skills

performer applies force to an object to project it

ex: throwing, kicking, striking

early overarm throwing

-mostly arm action elbow pointed up, throw executed by elbow extension alone

Proficient Overarm Throwing for Force

-Thrower uses preparatory windup (weight shifts and trunk rotates back; arm swings).

-Thrower uses opposite leg, long step, and differentiated trunk rotation.

-Upper arm and forearm lag.

-Movements are sequential to transfer momentum.

Developmental Changes in Overarm Throwing

Trunk action

1.None, and no forward or backward movements

2.Block rotation

3.Differentiated rotation

Backswing

1.None

2.Shoulder flexion

3.Upward backswing

4.Downward, circular backswing

Upper arm action

1.Oblique

2.Aligned but independent

3.Lagging

Forearm action

1.No lag

2.Lag

3. Delayed lag

Foot action

1.No step

2.Homolateral step

3.Short contralateral step

4.Long contralateral step

Developmental Changes in Overarm Throwing: Childhood

-Throwers do not achieve same step for each body component at same time.

-Some step combinations are observed more frequently than others.

-Not everyone reaches the highest step in each component.

-Differences are observed between the sexes in throwing skill.

Developmental Changes in Overarm Throwing: Adulthood

-Older adults demonstrate moderately advanced steps.

-Differences are observed between the sexes.

-Ball velocities are moderate.

-Musculoskeletal constraints might influence movement patterns used.

-Change is slow, involves decline (and more variability) in performance, and is typically related to control rather than coordination.

Throwing for Accuracy

-Throwers may use lower developmental steps for accuracy throws than for the forceful throws

-When required to throw a greater distance, differences between throws are minimal

Kicking

-Kicker strikes ball with foot

-Kicker must have perceptual abilities and eye-foot coordination to make contact (kicking a moving ball is difficult for children)

Early Kicking

-No step is taken with non kicking leg

-Kicking leg pushes forward

Proficient Kicking

-Preparatory windup is used (trunk rotated back, kicking leg cocked, knee bent).

-Trunk rotates forward.

-Movement is sequential: thigh rotates forward; then lower leg extends.

-Arms move in opposition to legs.

Developmental Changes in Kicking

-movement pattern changes are not well documented

-developmental steps have not been validated

Punting

- the ball is dropped from the hands

- punting is more difficult than kicking for children

Early Punting

-Ball is tossed up rather than dropped

-Punter often contacts ball with toes rather than instep

Proficient Punting

-Arms are extended to drop ball before final stride.

-Arms then drop to sides and move into opposition to legs.

-Punter leaps onto supporting leg, swings punting leg vigorously up to make contact.

-Punting leg is kept straight; toes are pointed.

Developmental Changes in Punting: Arms

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

Developmental Changes in Punting: Legs

Ball-contact phase

1.No step or short step, ankle flexed

2.Long step, ankle extended

3.Leap and hop

Sidearm Striking

-Various body parts can be used.

-Implements can be used.

-Mechanical principles are similar for all striking tasks.

early sidearm 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 Sidearm Striking

-Sequences for foot and trunk in overarm throw can be used.

-Trend is toward use of trunk rotation (none, then blocked, then differentiated).

-Plane of swing progresses from vertical to horizontal

-Grip changes from power grip to "shake-hands" grip.

-Elbows are held away from body and extended before contact.

Overarm Striking

-Without an implement (e.g., volleyball serve)

-With an implement (e.g., tennis serve)

Early Overarm Striking

-Trunk rotation is limited.

-Striker swings with collapsed elbow.

-There is little or no lag with swing forward.

-Movement looks like early throwing.

Proficient Overarm Striking

-Lower and upper trunk are rotated more than 90 degrees.

-Elbow is held between 90 and 119 degrees 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 (2° to 89°)

3. Ideal angle (90° to 119°)

Spinal and pelvic range of motion:

1. Rotation of less than 45°

2. Rotation of 45° to 89°

3. Rotation of 90° or more

Racket action:

1. No racket lag

2. Racket lag

3. Delayed racket lag

Overarm Striking: Older Adults

- Older adults appear to maintain coordination of ballistic movements fairly well.

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 older golfers were just as accurate as younger golfers.