UPPER BODY MUSCULATURE OF THE UNDERHAND SOFTBALL PITCH  

Sources include Alexander, M.J., Haddow, J.B., (1), Maffet, Mark W., Jobe, Frank W., Pink, Marilyn M., Brault, John, Mathiyakom, Witaya, (2), Barrentine, Steven W., Fleisig, Glenn S., Whiteside, James A., Escamilla, Rafael F., Andrews, James R., (3), Heitman, Robert J., Pugh, Steven F., Erdman, Joel W., Kovaleski, John E., (4), and Meister, Keith (5).

The goal of the underhand pitch is to use the body in such a way as to sequentially develop its potential energy through sequential segmentation which is converted to kinetic energy that is imparted to the ball in a smooth, fluid, and efficient manner. 

BIOMECHANICS:   Research has shown that the major contributor to final limb velocity is the joint with the highest angular velocity prior to release (1).  It has also been shown that optimal velocity at the distal end of a lever is produced by a  slowing down of the proximal segments.  This deceleration of the proximal segments of a chain have the effect of acceleration of the more distal segment creating a transfer of angular momentum from the decelerated segment to the distal segment thus producing an increased angular velocity of that segment (1).

Because the distal segment lags behind the more proximal segment during proper mechanics of a ballistic movement the stretch reflex mechanism is facilitated. The more the angular velocity of the distal segment is delayed, i.e. the more the distal segment trails the proximal one, the greater the stretch reflex mechanism of the agonist muscle group. This stretch excites the muscle spindles and the joint receptors and causes a more forceful contraction of those muscles during the subsequent joint movements.  This stored elastic energy is utilized when a concentric contraction immediately follows an eccentric contraction. Skilled performance is most likely dependent on the ability of the performer to decelerate  proximal segments in order, which then transfers momentum and stored energy from proximal to distal segments.

WIND-UP
Defined as the time of initial movement to lead toe-off (forward to the 6 o’clock position).  During this phase the anterior deltoid achieves 25% MMT (+ or – 11), the supraspinatus achieves 34% MMT (+ or –17), the infraspinatus achieves 24% MMT (+ or –13), and the serratus anterior achieves 23% MMT (+ or-9) (2).

INITIAL STRIDE
Defined as the time of lead toe-off to weight shift to the ipsilateral or pivot foot, arm elevation to 90 degrees, and trunk rotation of 90 degrees to the ipsilateral side (6 o’clock to 3 o’clock).  During this phase the infraspinatus achieves 93% MMT (+ or -52) which is its maximum during the pitch, the supraspinatus achieves 78% MMT (+ of -36), the anterior deltoid achieves 38% MMT (+ or - 29), the serratus anterior achieves 38% MMT (+ or -19), the posterior deltoid (eccentrically) achieves 37% MMT (+ or -27), and the subscapularis achieves 34% MMT (+ or -23), (2). 
The supraspinatus acts to maintain humeral head centralization with the glenoid cavity providing a fulcrum for deltoid elevation of the humerus and preventing superior translation of the humeral head during elevation.  The infraspinatus and subscapularis work to achieve arm elevation with the infraspinatus more active in internal rotation (2).

STRIDE COMPLETION
Defined as the time from initial weight shift to the ipsilateral foot to contralateral or lead foot touch down and arm elevation from 90 degrees to 180 degrees (3 o’clock to 12 o’clock).  During this phase the posterior deltoid achieves 102% MMT (+ or -42) which is its maximum during the pitch, the infraspinatus achieves 92% MMT (+ or -38), the teres minor achieves 87% MMT (+ or -21) which is its maximum during the pitch, the supraspinatus achieves 43% MMT (+ or -32), and the subscapularis achieves 41% MMT (+ or -33).

The posterior deltoid and the teres minor are working primarily to achieve external rotation as well as assisting with arm elevation. The infraspinatus works to help with the intense external rotation at the glenohumeral joint.  Along with arm elevation and external rotation , these muscles work to maintain glenohumeral stabilization (2).

LOWER BODY LEG DRIVE
Defined as the time from contralateral foot contact and arm elevation at 180 degrees to beginning of weight shift to the contralateral foot  and arm adduction to 90 degrees (12 o’clock to 9 o’clock).  During this phase the subscapularis achieves 81% MMT (+ or -52), which is its maximum during the pitch, the pectoralis major achieves 63% MMT (+ or -23), the teres minor achieves 57% MMT (+ or -21), the posterior deltoid achieves 52% MMT (+ or -25), and the serratus anterior achieves  45% MMT (+ or -39).

The pectoralis major contracts maximally during this phase as the arm is brought from a superior position down and forward across the trunk. The pectoralis major provides the force for this arm adduction and limited internal rotation.  The serratus anterior works together with the pectoralis major and an increase in pectoralis major activity is accompanied by an increase in serratus anterior activity.  The serratus anterior is working to stabilize the scapula against the acceleration forces of the pectoralis major on the humerus. The subscapularis is firing during this phase acting to assist with humeral internal rotation and to protect the anterior capsule of the glenohumeral joint (2).

BALL RELEASE
Defined as the time of initial to complete weight shift to the contralateral foot and completion of arm adduction (9 o’clock to 6 o’clock).  During this phase the muscle activity initiated during the previous phase is continued. The pectoralis major achieves 76% MMT (+ or -24), which is its maximum during the pitch, the subscapularis achieves 75% MMT ( + or -36), the posterior deltoid achieves 62% MMT (+ or -29), the serratus anterior achieves 61% MMT (+ or -19), which is its maximum during the pitch, and the anterior deltoid achieves 43% MMT (+ or -38), which is its maximum during the pitch.

The pectoralis major continues to perform the powerful adduction and internal rotation of the humerus, the serratus anterior continues to work in synchrony with the pectoralis major to stabilize the scapula and maintain glenohumeral stability. The subscapularis contributes to humeral internal rotation and stabilizes the anterior capsule of the glenohumeral joint (2).

FOLLOW THROUGH
Defined as the time from ball release to ceasation of forward arm movement and release of the ipsilateral foot and completion of the step.  During this phase most of the activity is in the teres minor which achieves 44% MMT (+ or -11), the serratus anterior achieves 40% MMT (+ or -14), the posterior deltoid achieves 34% MMT (+ or -29), and the pectoralis major achieves 33% MMT (+ or -20).  In most instances the muscles are contracting eccentrically to slow the arm down and bring it to a stop.

UPPER BODY UNDERHAND PITCHING MUSCLE
ORIGINS AND INSERTIONS 

DELTOID
Origin:  1) front outer 1/3 of the clavicle, 2) border of acromion, 3) lower edge
              of scapula spine.
Insertion:  deltoid tuberosity

SUPRASPINATUS
Origin:  supraspinous fossa
Insertion:  top of greater tubercle of the humerus

INFRASPINATUS
Origin:  below spine and lateral border of posterior scapula
Insertion:  greater tubercle of humerus (posterior side)

TERES MINOR
Origin:  below spine and lateral border of posterior scapula
Insertion:  greater tubercle of humerus (posterior side)

SUBSCAPULARIS
Origin:  anterior surface of subscapular fossa
Insertion:  lesser tubercle of humerus (anterior side)

SERRATUS ANTERIOR
Origin:  surface of upper 9 ribs at the side of the chest
Insertion:  costal aspect of whole length of the medial border of the scapula

PECTORALIS MAJOR
Origin:  1) inner ½ of anterior surface of clavicle, 2) anterior surface of costal
              Cartilages of first 6 ribs, 3) adjoining portion of sternum
Insertion:  flat tendon 2 to 3 inches wide to outer lip of intertubercular groove
                 of humerus 

UNDERHAND PITCHING MUSCLE EXERCISES 

DELTOIDS
back press---front press--- dumbbell press---front one arm and two-arm dumbbell raises---front barbell raises---low pulley lateral raises---low pulley front raises

SUPRASPINATUS
same as deltoids

INFRASPINATUS
low pulley bent-over lateral raises---bent-over dumbbell lateral raises---bent rows---T-bar rows

TERES MINOR
low pulley bent-over lateral raises---bent-over dumbbell lateral raises---dumbbell pullovers---bent rows

SUBSCAPULARIS
chin-ups---parallel bar dips---bent over rows---dumbbell pullovers---barbell pullovers---seated rows---one arm rows---bent rows

SERRATUS ANTERIOR
incline press---incline dumbbell press---dumbbell pullovers---barbell pullovers

PECTORALIS MAJOR
one arm dumbbell front raises---barbell front raises---front press---dumbbell press---bench press---incline bench press---push-ups---parallel bar dips---dumbbell flys---incline dumbbell flys---cable crossover flys---barbell pullovers---dumbbell pullovers