Chapter 7 Development of Ballistic Skills. Ballistic Skills An individual applies force to an object in order to project it. Common ballistic skills include

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7

Development of Ballistic Skills

Ballistic Skills

• An individual applies force to an object in order to project it.

• Common ballistic skills include throwing, kicking, and striking.

Overarm Throwing

• Throwing takes many forms:– Two-hand underhand– One-hand underhand– Sidearm– Two-hand overarm– One-hand overarm

• The most common in sport games is the one-hand overarm throw.

Gauging Throwing Skill• Product measures (outcome)

– Accuracy– Distance– Ball velocity

• Process measures (movement pattern) – Developmental sequences

• Each has advantages and disadvantages, but product measures often reflect skill as well as body growth and maturation during childhood and adolescence.

A Beginning Thrower

(continued)

Drawn from film tracings available from the Motor Development Film Collection,

Bowling Green State University

A Beginning Thrower (continued)

(continued)



A Beginning Thrower (continued)

Click image to view video

Characteristics of Early Overarm Throwing

• Early overarm throwing consists mostly of arm action.

• The elbow points up.• The throw is executed by elbow extension

alone.

A Proficient Thrower


Proficient Overarm Throwing for Force

• Preparatory windup used (weight shifts and trunk rotates back, arm swings).

• Use of opposite leg, long step, and differentiated trunk rotation.

• Upper arm and forearm lag back.• Movements are sequential to transfer

momentum.

Developmental Changes in Overarm Throwing

Trunk action1. None or forward–backward movement2. Block rotation3. Differentiated rotation

Backswing1. None2. Shoulder flexion3. Upward backswing4. Downward, circular backswing

(continued)

Developmental Changes in Overarm Throwing (continued)

Foot action

1. No step

2. Homolateral step

3. Short contralateral step

4. Long contralateral step

(continued)

Developmental Changes in Overarm Throwing (continued)

Upper arm action

1. Oblique

2. Aligned but independent

3. Lag

Forearm action

1. No lag

2. Lag

3. Delayed lag

Progression in Childhood

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

• Some combinations of steps are observed more frequently than others are observed.

• Not everyone reaches the highest step in each component; girls and women often remain in intermediate steps.

Throwing in Adulthood

• Older adults demonstrate moderately advanced steps.

• Gender differences are observed.• Ball velocities are moderate.• Musculoskeletal constraints might influence

the movement patterns used.

(continued)

Throwing in Adulthood (continued)

• Change is usually slight rather than rapid, is more often an increase in variability, and is usually a decline.

• Change is typically in the control of movements (slowed speed or decreased range of motion) rather than coordination of movements.

Throwing for Accuracy

• Throwers may use lower developmental steps for accuracy throws than for forceful throws.

• If the distance for the accuracy throw still requires force, little change would be noted for that individual.

Kicking

• The ball is struck; this can be difficult for children if the ball is moving.

• Children must have perceptual abilities and eye–foot coordination to make contact.

Characteristics of Early Kicking

• No step with nonkicking leg.

• Kicking leg pushes forward.


Intermediate Kicker


Proficient Kicking

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

• Trunk rotates forward.

• Movement is sequential, with thigh rotating forward then lower leg extending.

• Arms move in opposition to the legs.

Proficient Kicker


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 for children than kicking.

Characteristics of Early Punting

• Ball is tossed up rather than dropped.

• Punter often contacts ball with toes rather than with instep.



Proficient Punting

• Arms are extended to drop ball before final stride is taken.

• Arms then drop to sides and move into opposition with legs.

• Punter leaps on to supporting leg, swings punting leg vigorously up to contact.

• Punting leg is kept straight, with toes pointed.

An Advanced Punter



Developmental Changes in Punting: Arms

Ball-release phase1. Upward toss2. Late drop from chest height3. Late drop from waist height4. Early drop from chest height

Ball-contact phase1. Arms drop2. Arms abduct3. Arm opposition

Developmental Changes in Punting: Legs

Ball-contact phase

1. No 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.– Focus here is on one-hand sidearm and one-hand

overarm with an implement.– Principles can be applied to other striking tasks.

Characteristics of Early Sidearm Striking

• Chopping motion (elbow extension)

• Little leg and trunk movement


Intermediate Striker




Proficient Sidearm Striking

• Sideways preparatory stance and a long step

• Differentiated trunk rotation

• Horizontal swing through large range of motion, with arm extended before contact

• Sequential movements


Developmental Changes in Sidearm Striking

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

• Trend to use trunk rotation (none, then blocked, then differentiated).

• Plane of the swing progresses from vertical to horizontal.

(continued)

Developmental Changes in Sidearm Striking (continued)

• Grip changes from power grip to “shake-hands” grip.

• Elbows are away from the body and extended before contact.

Overarm Striking

• Without an implement (volleyball serve)

• With an implement (tennis serve)

Characteristics of Early Overarm Striking

• Limited trunk rotation

• Swing with a collapsed elbow

• Little or no lagging with the swing forward

• Looks much 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 overarm throwing

• Preparatory trunk action– No trunk– Minimal trunk rotation– Total trunk rotation

(continued)

Developmental Changes in Overarm Striking (continued)

Elbow action in ball-contact phase1. Very small or very large angle2. Intermediate angle (2–89 degrees)3. Ideal angle (90–119 degrees)

Spinal and pelvic range of motion1. Less than 45 degrees2. Rotation of 45 to 89 degrees 3. Rotation of 90 degrees or more

(continued)

Developmental Changes in Overarm Striking (continued)

Racket action

1. No racket lag

2. Racket lag

3. Delayed racket lag

Older Adult Striking

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 for the

same shot compared with younger golfers.– A few older golfers were less accurate than younger

golfers but most were just as accurate.

(continued)

Older Adult Striking (continued)

Haywood & Williams (1995)– Studied tennis “first” serve.– Studied older servers at moderate levels.– Two former teaching professionals were categorized

at the highest levels (they maintained the coordination of movements).

Ballistic Skills: Summary

• Proficient performance demonstrates the mechanical principles.

• Developmental trends are toward proficient mechanical performance.

• A forward step and more trunk rotation are used.

• Trunk rotation is differentiated.

(continued)

Ballistic Skills: Summary (continued)• Projecting limb shows more and more lag.

• Probably not all individuals reach highest steps.

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

Assessment of Ballistic Skills• Developmental sequences can be used as

checklists.• Individuals are considered to be in a developmental

step if the majority of a set number of executions (typically five) are in that category.

• Observation should be conducted from the appropriate direction.– Side views show forward step, trunk action, and lagging.– Rear views show arm angles.

Documents

Chapter 7 Development of Ballistic Skills. Ballistic Skills An individual applies force to an object in order to project it. Common ballistic skills include