CHAPTER 17: MOVING OBJECTS: THROWING, STRIKING, AND KICKING KINESIOLOGY Scientific Basis of Human Motion, 12th edition Hamilton, Weimar & Luttgens Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University Revised by Hamilton & Weimar Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin

Objectives Classify activities involving throwing, kicking, or striking patterns according to the nature of the force application. Name and discuss anatomical and mechanical factors that apply to throwing, kicking, or striking activities. Perform a kinesiological analysis of a sequential throwing, kicking, or striking skill under each of these force application conditions: momentary contact; projection; continuous application.

SEQUENTIAL MOVEMENTS Movement of body segments resulting in the production of summated velocity at the end of the kinetic chain of segments. Path produced is curvilinear. Most frequently used to produce high velocities in external objects. Depending on objective of skill (speed, accuracy, distance, or combination) modifications to the pattern may be made. I would like to leave accuracy in to account for pitching.

Joint Action Patterns Each pattern involves a preparatory movement referred to as a backswing, or wind up. This is followed by establishment of a base of support prior to initiation of the force phase. Ends in a follow through.

Overarm Pattern Characterized by rotation of the shoulder joint. Backswing: abducted arm rotates externally. Force phase: arm rotates internally. Some elbow extension, wrist flexion, and spinal rotation. Rotation of pelvis at the hip joint of opposite limb, resulting in internal rotation of the thigh.

Overarm Pattern Fig 17.2

Underarm Pattern Consists of forward movement of extended arm. Basic joint action is arm flexion. Fig 17.4

Sidearm Pattern Basic movement is internal rotation of the pelvis on the opposite hip, arm usually in an abducted position. Arm is moved forward due to pelvic and spinal rotation. Spine laterally flexes toward throwing arm. Elbow maintains or is extended slightly. Wrist flexion may also be part of the action.

Sidearm Pattern Fig 17.5

Kicking Pattern Modification of a locomotor pattern in which force is imparted to an object during forward swing of non-weight bearing limb. Non-kicking foot is stabilized. Pelvis is fixed over thigh & rotated toward support leg. Kicking leg lags behind; hip abduction & hyperextension. Kicking leg flexes at hip followed by knee extension.

Kicking Pattern Fig 17.6

Nature of Force Application Momentary Contact: striking and kicking. Sequential movement designed to bring about contact made with an object by a moving body part or implement. Projection: throwing An object is given some velocity and is released at the desired point.

PRINCIPLES RELATING TO THROWING, STRIKING AND KICKING Anatomical Principles Muscles contract more forcefully if they are first stretched. Unnecessary movements and tension mean awkwardness and fatigue. Skillful performance can be developed only by practice. Most efficient type of movement is ballistic. Appropriate levers should be used.

Mechanical Principles Throwing The object will move only if the force is of sufficient magnitude to overcome the object’s inertia. The pattern and range of joint movements depends on the purpose of the motion. Force exerted by the body will be transferred to an external object in proportion to the counterforce of the feet against the ground.

Mechanical Principles Throwing Linear velocity is imparted to external objects as a result of angular velocity of the body segments. Optimum summation of internal force is needed if maximum force is to be applied to an object. For a change in momentum to occur, force must be applied over time.

Mechanical Principles Throwing Force applied in line with an object’s center of gravity will result in linear motion of the object. If the force applied to object is not in line with it’s center of gravity, it will result in rotary motion of the object.

Striking, Hitting, and Kicking Major factors in the speed of a struck ball: Speed of incoming ball & striking implement. Mass of the ball & striking implement. Elasticity between ball & striking implement. Direction of ball & implement at impact. Point of impact between ball & implement.

Mechanical Principles Striking, Hitting, and Kicking The direction in which the object moves is determined by direction of force applied. Momentum is conserved in all collisions. Any change in momentum in colliding objects is related to force and duration of collision. The greater the velocity of the approaching ball, the greater the velocity of the ball in the opposite direction after it is struck.

Mechanical Principles Striking, Hitting, and Kicking The greater the velocity of the striking implement at contact, the greater the velocity of the struck ball. The greater the mass of the ball (up to a point) the greater its velocity after contact. The greater the mass of the striking implement (up to a point) the greater the striking force, therefore the greater the speed of the ball.

Mechanical Principles Striking, Hitting, and Kicking The higher the coefficient of elasticity of the ball and of the striking implement, the greater the speed of the struck ball. The direction taken by the struck ball is determined by four factors: Direction of striking implement at contact; Relation of the striking force to ball’s center of gravity; Degree of firmness of grip and wrist at contact; Laws of rebound.

EXAMPLES OF THROWING AND STRIKING Analysis of the Overarm Throw This analysis includes joint actions, muscle activity, and mechanics of the upper extremity only.

Analysis of the Overarm Throw Backswing Places joints in optimal position and involves the greatest number of segments in preparation for the force phase. Includes pelvic and trunk rotation in the opposite direction, horizontal abduction and lateral rotation at shoulder joint with elbow flexion and wrist hyperextension. Forward step taken with the opposite foot permits greatest ROM in trunk and pelvis, and a large base of support.

Analysis of the Overarm Throw Force Phase Following establishment of a base of support, pelvis and then trunk rotation are accompanied by lateral flexion away from the ball. Trunk motion causes increased horizontal abduction and lateral rotation at the shoulder joint. Elbow extension is followed by rapid medial rotation at shoulder, forearm pronation, then flexion and ulnar deviation at wrist. Ends with release of the ball.

Analysis of the Overarm Throw Follow-through From ball release until the momentum in the arm can be safely dissipated as the arm continues across the body in a downward direction. A forward step is also used.

Analysis of the Overarm Throw Actions proceed from proximal (more massive) to distal (lighter) segments. Momentum is transferred from more massive (proximal) to less massive (distal) segments, significantly increasing the velocity. Linear velocity at the end of the chain (ball at release) often can exceed 90 mph. Legs provide the stable base, contribute significantly to force production and transfer of momentum.

Analysis of the Overarm Throw Shoulder Joint Actions Lateral rotation preceding the medial rotation, controlled by eccentric contraction of medial rotators followed by concentric contraction of the same medial rotators. Height of humerus is controlled by static contraction of middle deltoid. Deltoid & supraspinatous contract concentrically during backswing to position upper arm, and eccentrically during the follow-through to help decelerate the arm.

Analysis of the Overarm Throw Other Muscles Involved Biceps has peak activity as the elbow is flexed late in backswing, at the beginning of force phase, and again during follow-through. Latissimus dorsi, active during medial rotation, remains active eccentrically during follow-through. Trunk rotators are also active.

Analysis of the Overarm Throw Stretch Reflex An important facilitating mechanism in accelerating the lagging distal segments. The more rapid the stretch (eccentric contraction), the greater will be the facilitating effect on the resulting concentric contraction of the same muscle. To gain greatest benefit, no pause between wind-up and force phases.

Analysis of the Overarm Throw Other Reflexes As the trunk rotates under the stationary head (eyes focused on the target), tonic neck reflex may facilitate the strong acceleration occurring during the force phase. Asymmetric TNR facilitates chin side shoulder abductors and elbow extensors, precisely the arm position at release. Increased pressure on the hand and weight transfer to forward foot may produce an extensor thrust reflex. Facilitation of the lower limb extensor muscles. Facilitation of arm extensors.

Analysis: Forehand Drive in Tennis Description Objective is to send the ball over the net, deep into the opponent’s court close to the base line. Fig 17.7

Analysis: Forehand Drive in Tennis Starting Position: Player faces the net with feet about shoulder width apart, weight on the balls of the feet. Racket is held with a hand shake grip. Backswing: Player pivots entire body so that the non-racket side is toward the net. Racket is taken back at shoulder level, head of racket above the wrist, face turned slightly down. Weight is over the rear foot. Good catch!!

Analysis: Forehand Drive in Tennis Forward Swing Player flexes at the knees, drops racket below contact point, racket head above the wrist. Steps toward the ball with non-racket foot. Pelvis and spine rotate so trunk faces forward, and weight is shifted to forward foot as racket is swung forward and up. Racket face is perpendicular to court at ball impact, imparting topspin to the ball.

Analysis: Forehand Drive in Tennis Follow-Through Follow-through continues toward the intended target, with the racket arm swinging across the body and up.

Analysis: Forehand Drive in Tennis Anatomical Factors Action is ballistic in nature. Initiated by muscular force, continued by momentum, and terminated by the contraction of antagonistic muscles. Chief levers: arm, trunk, and racket. Fulcrum: at opposite hip joint. Point of force application: at a point on the pelvis representing combined forces of the muscles producing the movement.

Analysis: Forehand Drive in Tennis Anatomical Factors Resistance application point: at the center of gravity of the trunk-arm-racket lever. May be considered the point of contact with the ball at the moment of impact. Additional lever action due to rotation of the spine, horizontal adduction at shoulder, and flexion at wrist. Muscular Strength: shoulder abductors assisting with swing, & rotators of spine and pelvis.

Analysis: Forehand Drive in Tennis Mechanical Analysis Purpose is to return ball in the court, but also to make it difficult to return. Requires both high speed and accuracy. Force of impact: speed of racket at moment of contact. Straight backswing: ease of control, but must overcome inertia. Circular backswing: greater distance to build momentum.

Analysis: Forehand Drive in Tennis Mechanical Analysis Arm fully extended to increase lever length. Effort to resist force of ball is less when the racket lever arm is shortened. Takes less force to swing a shortened racket lever into position. Concentration of mass at shoulder level moving forward at impact ensures maximum speed of striking.

Analysis: Forehand Drive in Tennis Mechanical Analysis Skillful players use a heavier racket - greater mass of implement  greater striking force. A new ball and well strung racket ensure good coefficient of elasticity. Shift weight while striking the ball to increase ground reaction force imparted to body & ball. Firm wrist and grip are essential for maximum impulse to be applied by the racket to the ball.

Analysis: Forehand Drive in Tennis Mechanical Analysis Direction of struck ball is determined by: Direction of implement at impact. Relation of striking force to ball’s center of gravity (controls spin). Firmness of grip and wrist at impact. Angle of incidence.