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Overhead Throwing Biomechanics. Generally broken down into six phases Involves application of the kinematic link or kinetic chain to maximize the velocity output of a thrown object. Phases. Wind-up Stride Arm Cocking Arm Acceleration Arm Deceleration Follow Through. Wind-Up.
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Overhead Throwing Biomechanics Generally broken down into six phases Involves application of the kinematic link or kinetic chain to maximize the velocity output of a thrown object.
Phases • Wind-up • Stride • Arm Cocking • Arm Acceleration • Arm Deceleration • Follow Through
Wind-Up • Begins at the start of movement and ends when the lead leg is maximally lifted
Stride • The lead leg drives forward and both arms are abducted. • The throwing arm externally rotates. • The four rotator cuff muscles fire to hold the head of the humerus within the glenoid fossa. • The scapula rotates upward as the head of the humerus is seated within the glenoid fossa. (This positioning of the scapula is important to prevent injury.)
Stride • The Supraspinatus is the most active of the rotator cuff muscle during this cycle. • The remaining rotator cuff muscles (Infraspinatus, Teres Minor, and Subscapularis), although active, are less important. • The Deltoid is also very active at this stage.
Arm Cocking • This phase begins when the lead foot makes contact with the ground during the stride phase and ends when the throwing arm achieves its maximum external rotation. • Rotation of the hips and pelvis helps set up the rotation that will be transferred to the torso and shoulders.
Arm Cocking • Muscles acting at the shoulder and scapula position the glenoid fossa against the head of the humerus and stabilize the scapula. • Specifically these include the levator scapula, serratus anterior, rhomboids, trapezius, and pectoralis minor. • Incorrect function of these muscles and movements at this stage will alter the correct biomechanics and will eventually lead to injury.
Rhomboids Levator Scapula
Serratus Anterior Trapezius
Arm Cocking • The rotator cuff muscles maintain tension at this point to keep the head of the humerus stable inside the glenoid fossa. • The internal rotators of the shoulder will develop tension to slow down and prevent excessive external rotation.
Arm Acceleration • This is the quickest phase of the throw. (It usually lasts less than .1 seconds.) • This phase starts just after the shoulder reaches maximum external rotation and ends when the ball is released. • The internal rotators of the shoulder have been stretched like a coiled spring during the previous phase. They shorten rapidly, assisted by this spring-like effect, and produce very rapid internal rotation of the shoulder.
Arm Acceleration • The rotator cuff muscles help to keep the head of the humerus stabilized in the glenoid fossa. • The trapezius, rhomboids, levator scapula, and serratus anterior are also very important in keeping the scapula stable during this movement.
Arm Deceleration • This phase starts when the ball is released and ends when maximum internal rotation of the shoulder is reached. • The throwing arm is horizontally adducted and internally rotated to the neutral or anatomical position and the scapula is protracted. • Posterior muscles of the G-H Joint, especially the Teres Minor, slow down the movement at the shoulder while the retractors of the scapula slow down the scapular protraction.
Follow Through • The arm deceleration process helps reduce the force and therefore the stress on the joints and muscles involved • This phase begins when when the internal rotation of the shoulder ends and finishes when the thrower returns to a balanced position.
Follow Through • This part of the movement is designed to extend the time that it takes to come to a stop as well as distribute the forces to the body and leg. • The posterior muscles of the G-H Joint are very important to continue the deceleration process at the shoulder.
Follow Through • The serratus anterior is very active in stabilizing scapular rotation while the rhomboids and the middle part of the trapezius continue to slow down and reduce the force of scapular protraction.
