the throwing athlete
TRANSCRIPT
The Throwing Athlete
Michael RosenblatPT, CEP, NCCP(Triathlon), Dip(FLM), BASc(KIN), MSc(PT)
Contents
• Biomechanics of Throwing• Acquired and Adaptive Changes• Examination• Rehabilitation
Wind-up PhaseObjective• To position the body in the most
advantageous way possible to deliver the pitch
Biomechanics• The phase begins with dual legs stance• Weight is transferred onto the back
leg• Torso must rotate 90 degrees
Pathomechanics• Weak hip abductors and knee
extensors on the stance leg create an unstable base
• This causes distal components of the kinetic chain to compensate to maintain velocity
Weber A et al. Sports Med Arthrosc Rev 2014;22:72-79.
Stride PhaseObjective• To create linear velocity through
forward motion
Biomechanics• The stride phase concludes when
the lead foot of the stride leg contacts the ground
Pathomechanics• Lack of stance leg hip internal
rotation leads to premature “opening up” of the pelvis, affecting distal aspects of the kinetic chain
• Leads to upper extremity injuries
Weber A et al. Sports Med Arthrosc Rev 2014;22:72-79.
Arm Cocking PhaseObjective• To position the body in the most
advantageous way possible to deliver the pitch
Biomechanics• The phase begins with dual legs stance• Weight is transferred onto the back leg• Torso must rotate 90 degrees
Pathomechanics• Weakness in stride leg quadriceps can cause
poor force generation, creating instability• Causes overuse injuries of the shoulder and
elbow• Pitching motion with early trunk rotation,
increased maximal external rotation, and decreased elbow flexion lead to increase valgus torque on the elbow
Weber A et al. Sports Med Arthrosc Rev 2014;22:72-79.
Arm Acceleration Phase
Biomechanics• Begins with GH joint in MER and ends with ball release from thrower’s hand• Position of shoulder and elbow during acceleration and ball release are
important for velocity• 90 degrees of horizontal abduction (coronal abduction) can optimize strength
and minimize shoulder impingement
Weber A et al. Sports Med Arthrosc Rev 2014;22:72-79.
Arm Deceleration Phase
Biomechanics• Begins with ball release and concludes
when the shoulder reaches maximum internal rotation• Large eccentric loads are necessary to
decelerate the throwing arm
• The large internal rotation torque placed on the GH joint is counterbalanced by contraction of the rotator cuff external rotators (infraspinatus and teres minor)
Weber A et al. Sports Med Arthrosc Rev 2014;22:72-79.
Follow-Through Phase
Biomechanics• The thrower’s body weight and
momentum of ball release result in weight transfer to the stride leg
• The stride leg stabilizes and absorbs the body force of the pitch
• Most overuse injuries to the posterior arm or trunk occur during the deceleration or follow-through phase
Weber A et al. Sports Med Arthrosc Rev 2014;22:72-79.
Baseball Nodes and ConsequencesNode Normal Mechanics Pathomechanics Result To be Evaluated
Foot position Directly toward home plate Open or closed Increased load on trunk or shoulder
Hip and/or trunk flexibility and strength
Knee motion Stand tall Increased knee flexion Decreased force to arm Hip and knee strength
Hip motion Facing home plate Rotation away from home plate
Increased load on shoulder and elbow
Hip and trunk strength
Trunk motion Controlled lordosis Hyperlordosis and back extension
Increased load on abdominals and “slow arm”
Hip and trunk strength
Scapular position Retraction Scapular dyskinesis Increased internal and external impingement with increased load on rotator cuff muscles
Scapular strength and mobility
Shoulder/scapular motion Scapulohumeral rhythm with arm motion (scapular retraction/humeral horizontal abduction/humeral external rotation)
Hyper angulation of humerus in relation to glenoid
Increase load on anterior shoulder with potential internal impingement
Scapular and shoulder flexibility and strength
Elbow position High elbow (above 90° abduction)
Dropped elbow (below 90 abduction)
Increased valgus loads on elbow
Scapular position and strength, trunk and hip flexibility and strength
Hand position On top of ball Under or side of ball Increased valgus load on elbow
Shoulder and elbow position
Kibler W et al. Clin Sports Med 2013;32:637-651
Acquired and Adaptive ChangesRange of motion• Increase in glenohumeral external rotation (10 to 15 degrees)• Decrease in GH internal rotation (10-15 degrees)• GIRD (glenohumeral internal rotation deficit)
– Loss of IR of affected arm (> 25 degrees)– Total arc of motion (TAM) deficit
Bony• Increase in humeral retroversion (HR)
– Correlated with GIRD• Glenoid also undergoes adaptive retroversion
– Allows an increase in ER of the humerus before physiological limit
Scapular• Decreased upward rotation leads to increase injury rates• Capsular tightness can lead to increase protraction
– Causes decrease strength and decreased sub-acromial space
Tokish J et al. Sports Med Arthrosc Rev 2014;22:88-93
ExaminationObservation• Bilateral evaluation for shoulder girdle
musculature atrophy, scapular resting position, evidence of prior injury
Range of motion• Decreased ROM in the hip and trunk
– Compare hip internal and external rotation
• Total arc of motion (TAM)• Abnormal scapulohumeral rhythm
– Early protraction and abduction (GIRD)
Stability• AC and SC joints
Strength• Hip and trunk
– 1-leg stability series• Standing balance test• Single leg squat
• Rotator cuff musculature– External rotators should be at 80% of
internal rotators
Special tests• Scapular assistance test (SAT)
– Can evaluate scapular contribution to impingement
• Scapular retraction test (SRT)– Evaluates scapular contribution to
supraspinatus weakness
Provencher M et al. Sports Med Arthrosc Rev 2014;22:80-87.
Examination: Scapular Assistance Test
The SAT can be used to evaluate scapular contributions to impingement and rotator cuff strength by assessing muscle weakness. To perform the test, the practitioner applies gentle pressure on the inferior medial scapular angle as the patient elevates the arm. This assists the serratus anterior and lower trapezius muscles in upward rotation and posterior tilt of the scapula causing reduced subacromial impingement and optimizing the length of the rotator cuff muscles. A positive result is when the patient notes increased arc of motion without pain or impingement symptoms.
Provencher C et al. Sports Med Arthrosc Rev 2014;22:80-87
Examination: Scapular Retraction Test
The SRT is used to evaluate scapular protraction contribution to supraspinatus muscle weakness. Strength of supraspinatus is initially assessed with the arm in the “empty can” position. The scapula is then manually stabilized in a retracted position and strength testing is per- formed again. A positive test is when there is an increase in strength (although not a decrease in pain) with the scapula stabilized
Provencher C et al. Sports Med Arthrosc Rev 2014;22:80-87
Examination: Proximal to Distal Kinetic Chain
Examination Emphasis Normal Abnormal Result Evaluation
One leg stability: stance Negative Trendelenburg Positive Trendelenburg Decrease force to shoulder Decrease force to shoulder
One leg stability: squat Control of knee varus/valgus during decent
Knee valgus or corkscrewing during decent
Alters arm position during task
Dynamic postural control
Hip rotation Bilateral symmetry within known normal limits
Side-to-side asymmetry and/or not within normal limits
Decrease trunk flexibility and rotation
Internal and external rotation of hip
Plank Ability to maintain body position for at least 30 s
Inability to maintain body position
Decreased core stability and strength
Dynamic postural control in suspended horizontal position
Scapular dyskinesis Bilateral symmetry with no inferior angle or medial border prominence
Side-to-side asymmetry or bilateral prominence of inferior angle and/or medial border
Decreased rotator cuff function and increased risk of internal and/or external impingement
Scapular muscle control of scapular position (“yes/no” clinical evaluation manual corrective maneuvers)
Shoulder rotation Side-to-side symmetry or internal and external rotation values less than 15 or less than 5
Side-to-side asymmetry of 15 or more in internal and/or external rotation or 5 or more of total range of motion
Altered kinematics and increased load on the glenoid labrum
Internal and external rotation of glenohumeral joint
Kibler W et al. Clin Sports Med 2013;32:637-651
Examination: Proximal to Distal Kinetic Chain
Examination Emphasis Normal Abnormal Result Evaluation
Shoulder muscle flexibility Normal mobility of pectoralis minor and latissimus dorsi
Tight pectoralis minor and/or latissimus dorsi
Scapular protraction Palpation of pectoralis minor and latissimus dorsi
Shoulder strength Normal resistance to testing in anterior and posterior muscles
Weakness and/or imbalance of anterior and posterior muscles
Scapular protraction, decreased arm elevation, strength, and concavity- compression
Muscle strength from a stabilized scapula
Joint internal derangement All provocative and stress testing negative
Pop, click, slide, pain, stiffness, possible “dead arm”
Loss of concavity-compression and functional stability
Labral injury, rotator cuff injury or weakness, glenohumeral instability, biceps tendinopathy
Kibler W et al. Clin Sports Med 2013;32:637-651
Rehabilitation: Scapular Dyskinesis
1. Begin with ROM exercises of the hip and spine2. Stretching – Trapezius, pectoralis minor, levator scapula, teres
minor, infraspinatus, latissimus dorsi3. Scapular protraction and retraction exercises4. Strength protocol
a. Closed kinetic chain exercises first(focus on serratus anterior and trapezius)b. Advanced Throwers Ten
Rehabilitation:Early Isometric Scapular Exercises
Inferior Glide
Low Row
Kibler W et al. Am J Sports Med 2008;36(9):1789-1798
Rehabilitation:Early Dynamic Scapular Exercise
Robbery
Kibler W et al. Am J Sports Med 2008;36(9):1789-1798
Lawnmower
Rehabilitation:Average Amplitude EMG Activity
Inferior Glide Low Row Lawnmower Robbery
Upper Trapezius
8.1 (5.9) 10.4 (8.1) 21.8 (15.7) 31.6 (16.7)
Lower Trapezius
19.4 (26.6) 15.4 (11.6) 30.5 (19.2) 27.0 (20.8)
Serratus Anterior
23.4 (19.6) 28.2 (20.8) 25.5 (21.4) 20.9 (16.8)
Anterior Deltoid
4.6 (2.4) 16.6 (13.3) 5.5 (3.6) 7.4 (5.5)
Posterior Deltoid
8.6 (6.0) 42.4 (23.2) 16.2 (10.6) 14.0 (9.2)
Kibler W et al. Am J Sports Med 2008;36(9):1789-1798
References1. Kibler W et al. Electromyographic analysis of specific exercises for scapular control in early
phases of shoulder rehabilitation. Am J Sports Med 2008;36(9):1789-1798
2. Kibler W et al. Pathomechanics of the throwing shoulder. Sports Med Arthrosc Rev 2012;20:22-29.
3. Kibler W et al. Mechanics and pathomechanics in the overhead athlete. Clin Sports Med 2013;32:637-651
4. Provencher M et al. The role of the scapula in throwing disorders. Sports Med Arthrosc Rev 2014;22:80-87.
5. Tokish J et al. Acquired and adaptive changes in the throwing athlete: implications on the disabled throwing shoulder. Sports Med Arthrosc Rev 2014;22:88-93.
6. Weber A et al. The biomechanics of throwing: simplified and cogent. Sports Med Arthrosc Rev 2014;22:72-79.