Biomechanics, NTUPT 2003

Throwing and Striking

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Sequential Movements of the Body Segments
Biomechanics of Throwing
Biomechanics of Striking

Hamilton, N., & Luttgens, K. 2002. Kinesiology, Scientific Basis of Human Motion, 10^thed. Chapter 18, pp. 450-466.

Objectives: After studying this topic, the students will be able to

identify the sequential movement and give examples

classify sports activities involving sequential movements according to the nature of force application

identify the mechanical factors that affecting to throwing, striking, or kicking

Sequential Movements of the Body Segments

Definition of Sequential Movement

the movement that involves a sequential action of a chain of body segments, leading to a high-velocity motion of external objects (Hamilton & Luttgens, 2002, p.451)

results in the production of a summated velocity at the end of the chain of segment used

the path of the external object motion is curvilinear in nature

examples

a pitcher throws a baseball

a young adult spikes a volleyball

a batter hits a baseball

an elderly drives a golf ball

a tennis player serves a tennis

Modification of Sequential Movement

objectives of sequential movements

skill

speed

accuracy

distance

components that are used to modify movement according to different objectives

numbers of body segment used

range of motion (ROM) used

lever length used

Classification by Nature of Force Application

momentary contact

force imparted to an object through temporally contact with that object by a moving part of the body segment or by implement held or attached on the body segment

the object may be either stationary or moving

examples：

on moving object： baseball striking, soccer heading or kicking, volleyball set, or tennis driving

on stationary object： golf

projection

force imparted to an object through the end of a chain of body segments in order to develop kinetic energy, followed by a high-velocity motion of that object

the object may be held in one hand or hands

examples：

for distance： shot put, javelin, or volleyball serving

for accuracy： baseball pitching or dart throw

continuous application

force imparted to an object with the force continuously applying to that object

examples：

against large resistance： pushing a desk or lifting weight

maintain a position while waiting for a release： archery

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Biomechanics of Baseball Throwing

Patterns of Throwing

overarm (overhead)

sidearm

underarm

Kinematics of Overarm Throwing

windup (cocking) phase shoulder horizontal abduction and fully external rotation (closed-packed position) trunk left rotation prone to have shoulder impingement syndrome acceleration phase shoulder internal rotation deceleration phase checked by shoulder external rotators follow-through phase trunk rotation

Kinematics of Sidearm Throwing

preparation phase

shoulder horizontal abduction only

trunk right rotation

acceleration phase

shoulder horizontal adduction

deceleration phase

checked by deltoid posterior

follow-through phase

opposite hip internal rotation

Kinematics of Underarm Throwing

preparation phase

shoulder extension

elbow extension

acceleration phase

shoulder flexion (arm flexion)

deceleration phase

checked by shoulder extensors

follow-through phase

trunk rotation

Mechanical Factors of Throwing

ballistic movement of one segment imparting force must overcome the inertial of an object mass of object internal resistance friction between object and supporting surface resistance to surrounding medium
force needed dependent on speed of object distance of throwing accuracy of target： related to direction of the object after its release direction of the object after release dependent on direction of the object at the moment of release： path tangential to the arc of motion gravity air or water resistance spin of the object
timing pattern of movement part The slowest or heaviest part must start to move first, and the quickest and lightestone last to facilitate use of stretch reflex

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Biomechanics of Striking

Forehand Drive in Tennis

action： the player takes the racket to hit the ball and send it into the opponent's court

type of movement： ballistic movement

participating lever： racket, racket-side arm, and trunk

location fulcrum： the hip joint at non-racket side

skill requirement： high speed and moderate accuracy

motion description

back swing phase

the player pivots his body to have the non-racket side face forward

the racket is taken back at the shoulder level

the body weight is over the foot of the racket side

the head of the racket is kept above the wrist

forward swing phase

the player lowers down his body by flexing the knee to have the racket below the intended contact point

the trunk rotates forward to shift the weight to the foot of the non-racket side

the racket is perpendicular to the ground at the moment of impact

follow-through phase

the body continues forward

the racket arm swings across the body and up toward the chin

the effect of body spinning

mechanical factors contributing the impact to the ball： the greater impart force will impart more momentum to the ball, leading to speed up the ball on its return flight

increase the lever-arm length by using a long-arm racket, keeping the arm straight

firmness of grip depends on

muscle strength of wrist and finger flexors

the angle of the racket face at ball hitting because the angle of rebound is highly correlated to the angle of incidence

actually, the ball is not a rigid body so that the angle of rebound is slightly less than the angle of incidence

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