Muscles and

Movement

Dan Foster, PhD, ATC

January 7, 2010

Rothbart B, May 2009

Athletic Training Assessment

• Skilled Movement Deficiency

• Rule-out life & limb threatening injuries» or

• Rule-out referral issues» or

• Functional status

Philosophy of approach for deficiencies and functional status: minor alterations in precision of movement lead to injury and pain, caused by changes in muscle length, strength, stiffness, and movement patterns

Key Elements

• Assessment of alignment– Indicates possible muscle length changes and joint

alignment– Interfere with optimal movement

• Movement patterns

• Specific muscle length and strength testing

Borstad J, Phys Ther, 2006

Whyte E, Gait & Post, 2010

Garner B, BioMed Engineer, 2004

Scapular & Humeral Alignment

• Vertebral border parallel to spine

• ~ 3 in. away• Between T2 – T7• Flat on chest wall• Rotated 30o anteriorly• Less than 1/3 protruding• Cubital fossa forward• Humerus vertical

Garner B, BioMed Engineer, 2004

Kibler W, AJSM, 1998

Alignment Issues

• Downwardly rotated

Scapular Motions

• Scapula variable during first 30o abd or 60o flex

• Remaining 120o Humeral and 60o Scapular

• Timing often 140o Humeral flex when scapula stops

Inman V, JBJS, 1944

Muscle Physiology and Control

• Strength• Length• Stiffness• Timing

Muscle Strength

• Capacity– Fiber number

– Contractile elements• Hypertrophy/Atrophy

– Arrangement• Series/Parallel

– Length of fibers

– Configuration• Overlapped, lengthened,

disrupted

Wilkie D, Br. Med Bull, 1956Tipton C, Am J Physiol, 1970

Muscle Length

• Prolonged elongation

• Strain injury and continuous tension

• Sustained stretching Kendall F, 1993

Muscle Stiffness

• Change in tension per unit change in length

• Contributes to movement patterns– Active and passive stiffness– A factor in compensatory motion in contiguous

joints Sahrmann S, 2002

Movement Timing

• Altered recruitment patterns– Upper trapezius dominance

• Learned

• Preferred pattern due to pain

• Delayed or insufficient action

• Stabilizing muscle causes movement

Case

• 16 YO ♀ swimmer with B shoulder pain R>L

• Cumul pain occurs in flex & abd at ~100o • Swimmer since 6, ranked high at one

time• Works hard, weight training & swim despite• 5’7” 127#• Slight thoracic kyphosis, weak abs• B shoulder girdle elevation, arms abd

• B scapular abd

• Humerus glides sup, at 120o flex humerus med rotates/pop, glide sup on return to neutral

• Trunk ext on shoulder flex to counterbalance– If trunk is stabilized, flex is limited

• Trapezius & Rhomboids are short (hard to determine)

• Deltoid & Supraspinatus are short

• Lat rotators are stiff

• Lower & mid Trapezius are weak

• Deltoid becomes dominant on ER – Humeral ext, winging, and humeral head glide sup

• On IR & ER immediately initiates scapular motion

• Serratus is weak and wings in quadruped position

Diagnosis?

• Impingement– Supraspinatus tendinopathy– Subacromial or subdeltoid bursitis– Bicepital tendinopathy

• Humeral superior glide – primary– During shoulder flexion with elbow flexion sx ↓

• Scapular abduction - secondary

Treatment

• Primary emphasis– Stretch deltoid and decrease dominance– Improve control of trapezius and serratus ant

• Learn how to control IR/ER without other motions (supine)

• Target infraspinatus and teres minor (prone & standing)

• Control scapula and sup glide on IR (prone)

Exercises

Outcome

• Within 4 weeks (no swimming)– Arms at side during rest– Arms flex without pain to 180 and w/o moving

trunk– No medial rotation with popping– Tolerates 4 pounds of load– Ready to step up her activity and resume

swimming when she can go through her stroke without popping

Summary

• Minor alterations in precision of movement lead to injury and pain, caused by changes in muscle length, strength, stiffness, and movement patterns

• The influence of multiple muscle interactions acting on multiple joints in functionally oriented tasks is where we might go with deficiency screening and rehab recovery