Module J
Throwlike and Pushlike Movement Patterns

Page 337: Questions # 1 to 3 inclusive and # 5 to 7 inclusive [answers in bold print]

1.    List three general movement patterns.  List three sport skills under each pattern.

Kicking - soccer place kick, flutter kick, punt

Striking - baseball batting, badminton stroke, golf

Pushing - basketball shot, weight lifting, push pass in field hockey

2.    How does one distinguish between a movement pattern and a sport skill?

A movement pattern is any configuration of movements in the same general spatial plane and s not specific to any one sport.

A sports skill is specific to a sport event and is associated with a particular mechanical purpose.

3.    List three sport skills displaying an overarm, and underarm, and a sidearm pattern.

Overarm - baseball pitch, tennis serve, javelin throw

Sidearm - tennis forehand stroke, baseball batting, discus throw

Underarm - bowling, softball pitching, horseshoe pitching

5.    How does Atwater distinguish between an overarm throw and a sidearm throw?

According to Atwater, in an overarm throw the body leans away from the throwing arm.  In a sidearm throw the body leans toward the throwing arm.

6.    List five open kinetic chain activities.  List five closed kinetic chain activities.

Open kinetic chain examples : dart throwing, reaching for a book, typing, kicking, bowling Closed kinetic chain examples: pull-ups, walking, jumping, pushups, squats

7.    How does one distinguish an open skill from an open kinetic chain activity?  How does one distinguish a closed skill from an closed kinetic chain activity?

An open skill has perceptual - motor demands, whereas an open kinetic chain is a mechanical phenomenon.

A closed skill lacks the perceptual motor demands of an open skill in that the performer need not react to information presented suddenly; a closed skill can be an open or closed kinetic chain movement.
 
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Page 345: Questions # 1 and # 3 to 6 inclusive [answers in bold print]

1.    Of the following activities, circle those to which the open kinetic link principle applies: a soccer punt, a golf swing, a right jab in boxing, a back handspring takeoff, hammering a nail, a hammer throw, pushing a table across the floor, a football pass for distance, bowling.

The kinetic link principle applies to the soccer punt, golf swing, hammering a nail, hammer throw, football pass for distance, and bowling.

3.    State three principles that relate to the use of body segments in generating velocity on the open end of the open kinetic chain.

There are several statements that can be made regarding the generation of velocity in an open kinetic link system.  These statements relate two or more factors to a velocity increase.  Several examples are as follows:

a.    Body segments are used in a sequential fashion from the more massive to the less massive segments.

b.    Body segments are used in a sequential fashion form the more proximal to the more distal segments.

c.    Body segments are used in a sequential fashion from the most stable to the most free segment.

d.    Distal body segments lag back as proximal segments accelerate forward.

e.    A more distal segment accelerates forward as its more proximal segment decelerates forward.

4.    Define the radius of gyration.  How does this concept relate to throwing an object or swinging an implement?

Radius of gyration is defined as a linear measure of the distribution of mass about an axis of rotation.  Radius of rotation is the linear distance from an axis of rotation to some point on a rotating body.  The radius of gyration is used to calculate the rotational inertia of a body whereas the radius of rotation is used to calculate the linear velocity of a rotating point.

During throwing, kicking and striking movements, the magnitude of the radius of gyration partially determines the amount of torque necessary to accelerate the extremity and implement.  The greater the radius of gyration, the greater torque will be needed to accelerate.  The magnitude of the radius of rotation partially determines the linear velocity of the object or the contact point on the he striking implement.  The greater the radius of rotation, the greater the linear velocity of a point given the same angular velocity.

5.    Define the radius of rotation.  How does this concept relate to swinging in implement.

The radius of rotation is defined as the distance between the axis of rotation and the point of impact or release of the object.  For a softball bat the radius of rotation for the wrist motion is the distance between the wrist axis and the place of impact of the ball on the bat.

Because the linear velocity can be calculated by multiplying the angular velocity of the implement by the radius of rotation, the greater the radius of rotation, the greater the linear velocity of the point of impact, assuming the angular velocity is the same.

6.    Describe the differences in the radius of gyration and the radius of rotation in relation to throwlike movements.  Relate these to linear and angular velocity.

The radius of gyration is defined as a measure of the average distribution of the mass of an implement.  It is part of the implement's rotational inertia, thus, the greater the radius of gyration, the greater the inertia and the smaller the angular velocity generated by a given torque.  Therefore, the greater the radius of gyration, the smaller will be an implement's angular velocity.

The radius of gyration is a squared term in the equation for rotational inertia, it has a squared inverse effect on the implement's angular velocity.  Reducing an implement's radius of gyration has a positive squared effect on increasing the implement's angular velocity; whereas, increasing the radius of rotation has a singular effect on increasing the implement's linear velocity.

7.    Attend a beginning class in badminton, tennis, or golf. Observe an unskilled performer and a skilled performer in the class, and compare the segments that are used and the sequencing (or lack of sequencing) of the segments in a similar skill.  Does the beginning performer use the same segments and movements?  Does the beginner sequences the movements, or are some of the movements used simultaneously?  What differences do you notice about the speed of the object projected by each?  the accuracy?

The student will find that the beginning or unskilled performer will use the joint movements in a simultaneous fashion rather than a sequential fashion, and will tend to use more of a lever-type action than a wheel and axle-type action.  In doing so, the beginner will sacrifice speed of the distal link and thus the projection velocity.  With the sacrifice in velocity, the beginner may increase accuracy of the shot by producing a more rectilinear path of the distal link from the simultaneous movements, and by using the lever-type mechanism.  The intermediate performer or newly skilled performer will be attempting to utilize the wheel and axle mechanism in a sequential fashion, thus achieving greater projection velocity.  In doing this, the performer may display inaccuracy at times.
 
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Page 347: Questions # 2 to 4 inclusive [answers in bold print]

2.    Discuss why it is impractical or impossible to position the hand using radial or ulnar flexion such that one could effectively use forearm (radioulnar) motions for added velocity in a baseball pitch, a tennis forehand stroke, or a basketball throw for distance.

Without an additional link, such as a racquet, the radial flexion does little to increase the radius of rotation for forearm pronation.  However, a tennis racquet or basketball may be too massive for one to be able to successfully increase the radius of rotation, that is, one would have to decrease the angular velocity of that rotation because the increase in rotational inertia would prevent great acceleration.

3.    Discuss the phrase "a longer lever gives more velocity."  Why is this statement misleading?  IN what kind of situations would a longer lever not provide more velocity?

There are two properties that contribute to greater linear velocity of a point, the radius of rotation and the angular velocity.  The length of the lever is used to mean its radius of rotation.  Only if the angular velocities are less than or equal to each other, will the longer lever give more linear velocity.

4.    List the advantages of using a wheel-axle motion rather than a lever motion when one wants to generate high end-point velocity on an implement.

The wheel-axle mechanism usually has a smaller radius of gyration and thus a smaller rotational inertia.  When equal torques are applied, the mechanism with the smaller rotational inertia will have greater acceleration.  The greater the acceleration, the greater the angular velocity will be at release or impact.  Thus a wheel-axle mechanism will probably impart a greater linear velocity tot he object being thrown or struck.

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Page 353: Questions # 1 to 4 inclusive [answers in bold print]

1.    List the primary mechanical purposes associated with pushlike patterns.  For each of the mechanical purposes, list five skills that have that purpose.

To manipulate a resistance - bench press, squat, passing a medicine ball, wrestling throw, boxing punch.

To project an object for maximum accuracy - darts, horseshoes, slow-pitch softball pitching, bunt, basketball shot.

2.    What four factors distinguish a pushlike pattern from a throwlike pattern?

Pushlike patterns are simultaneous segmental movements, the object to be pushed does not lag back of the segments doing the pushing, the object is pushed in a rectilinear path, and there is a predominance of lever movements.

3.    List five constraints of the activity, equipment, or performers that would have the effect of putting a pushlike element into an otherwise ideal throw-like pattern.

Weight or mass of the object to be thrown or struck, the maturity of the performer, the strength of the performer, when an element of accuracy is present for success, the rotational inertia of the striking implement.

4.    For each of the three paths shown in Figure J.13, draw an arrow to indicate the direction that an object moving along the path would travel if released at Point 1, 2, or 3.
        a.    Which path is rotary?
        b.    In which path is the timing of release the most critical to the accuracy of the projectile?
        c.    In which path is the timing of release the least critical?
        d.    Draw these paths:
                i.    The path of the head of a golf club.
                ii.   The path of the head of a tennis racket during a forehand drive.
                iii.   The path of the CG of the body just before and after leaving the horizontal bar during a dismount.
                iv.   The path of the discus before release.
                v.    The path of a basketball during a jump shot, before release.
 
a.    Path b is rotary; path c is rectilinear, path a is curvilinear.

b.    The rotary path, b.

c.    The rectilinear path, c.

d. below
    i.    The path of the head of a golf club is basically rotary, with the path assuming a fairly flat curvilinear
           path on either side of impact.

    ii.    The path of the head of a tennis racket is basically curvilinear with the path assuming a fairly flat arc
           on either side of impact.

    iii.   The center of gravity of the body will fly off in a rectilinear direction: however, gravity will immediately
           cause it to travel in a curvilinear (parabolic) path.

   iv.   The path of a discuss immediately prior to release is rotary, assuming no last moment contraction or
          relaxation of upper extremity musculature.

    v.   The ball will travel in a rectilinear path as a result of the simultaneous rotary motion of the fingers
          about the wrist axis, the forearm about the elbow axis, and the arm about the shoulder axis.