Development of Ballistic Skills

Chapter 6 notes – Development of Ballistic Skills  Ballistic Skills o Performer applies force to an object to project it o Examples: throwing, kicking, striking  Throwing o Forms  Underhand (one or two hand)  Sidearm  Overarm (one or two hand) o Assessment  Product measures (outcome): accuracy, distance, ball velocity  Process measure (movement pattern): developmental sequences o Early Overarm throwing  Throw involves mostly arm action  Elbow is pointed up  Throw is executed by elbow extension alone o 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  Validated Developmental Sequences o These are sequences of advances in the performance of a skill o They fall in the same fixed order for all individuals o Sequences have been confirmed by a longitudinal study o 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 o Throwers do not achieve the same step for each body component at the same time o Some step combinations are observed more frequently than others o Not everyone reaches the highest step in each component o Differences are observed between the sexes in throwing skill  Adulthood: o Older adults demonstrate moderately advanced steps o Differences are observed between the sexes o Ball velocities are moderate o Musculoskeletal constraints might influence movement patterns used o Change is slow, involves decline (and more variability) in performance, and is typically related to control rather than coordination  Throwing for Accuracy o Throwers may use lower developmental steps for accuracy throws than for forceful throws o When required to throw a greater distance, differences between throws are minimal  Which Approach to Judging o Why would an instructor use process measures to judge proficiency of throwing? o Why would an instructor use product measures to judge proficiency of throwing?  Kicking o Kicker strikes ball with foot o Kicker must have perceptual abilities and eye-foot coordination to make contact  Kicking a moving ball is difÏcult for children o Early Kicker  No step is taken with non-kicking leg  Kicking leg pushes forward o 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 o Developmental Changes in Kicking  Movement pattern changes are not well documented  Developmental steps have not been validated o Punting  The ball is dropped from the hands  Punting is more difÏcult than kicking for children o Early Punting  Ball is tossed up rather than dropped  Punter often contacts ball with toes rather than instep o 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 and swings punting leg vigorously up to make contact  Punting leg is kept straight; toes are pointed  Striking o Sidearm Striking  Various body parts can be used  Implements can be used  Mechanical principles are similar for all striking tasks o Early Sidearm Striking  Chopping motion (elbow extension)  Little leg and trunk movement o Intermediate striker  Trunk rotation  Lower body weight transfer  Larger range of motion in the arms o 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 o 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 o Overarm Striking  Without an implement (volleyball serve)  With an implement (tennis serve) o Early overarm striking  Trunk rotation is limited  Striker swings with collapsed elbow  There is little to no lag with swing forward  Movement looks like early throwing o Proficient overarm striking  Lower and upper trunk are rotated more than 90⁰  Elbow is held between 90⁰ and 119⁰ to start forward movement  Racket lags behind arm in forward swing  Movement is sequential o Developmental Changes in overarm striking  Trunk, upper and lower arm, and leg sequences similar to those for overarm throwing  Preparatory trunk action  No trunk rotation  Minimal trunk rotation  Total trunk rotation  Elbow action in ball-contact phase  Very small or very large angle  Intermediate angle(2⁰ to 89⁰)  Ideal angle (90⁰ to 119⁰)  Spinal and pelvic range of motion  Rotation of less than 45⁰  Rotation of 45⁰ to 89⁰  Rotation of 90⁰ or more