STRENGTH TESTING

STRENGTH TESTING

Supraspinatus

Jobe and Moynes advised examining the supraspinatus muscle with the shoulder internally rotated and abducted 90ยบ in the plane of the scapula ("empty can" or Jobe position). Worrell et al compared Jobe's position with the position recommended by Blackburn et al. The Blackburn test is performed with the subject in the prone position and the shoulder abducted by 100 and in lateral rotation with the thumb up. These researchers found that significantly greater EMG activity occurred when the supraspinatus muscle was tested in the Blackburn position. Similar studies found no significant differences in EMG activity in the supraspinatus muscle when the two positions were compared. Other EMG studies have compared muscle testing with the shoulder in 90 ° abduction in the plane of the scapula with external or internal rotation. No studies found a significant difference in supraspinatus muscle activity when the two positions were compared. However, these researchers recommended using the lateral rotation test (thumb up or "full can" position) because this is a position where less subacromial impingement and therefore less pain is expected. Itoi et al found that less pain occurs in the full can position compared to the empty can position (thumb down) when testing for supraspinatus tendon ruptures in patients. Therefore, it is recommended to test the supraspinatus muscle in the full position. It may not be possible to determine specific supraspinatus weakness because the deltoid muscle is always active with the supraspinatus muscle. Weakness detected with this muscle test is often the result of pain production that inhibits muscle contraction. Weakness in the absence of pain requires a differential diagnosis between a neurological source and a muscle or tendon rupture.

Infraspinatus and Teres Minor

Most EMG studies demonstrated no significant difference in the muscle activity of the infraspinatus when shoulder lateral rotation was performed concentrically during exercises or isometrically during muscle tests at 0, 45 , or 90  of shoulder abduction. However, Reinold et al  found a significant increase in infraspinatus activity when subjects exercise in the side-lying position with 0 of shoulder abduction as compared with the 90 abducted position. Investigators found that the infraspinatus muscle activity is best

isolated from the supraspinatus and posterior deltoid muscles with the shoulder in 0 of abduction and medially rotated approximately 45. The lateral rotator muscles should be tested in this position and at the end range of shoulder lateral rotation with 90 of abduction. In the second position, the glenohumeral joint

is less stable and requires more activity from posterior deltoid and other rotator cuff muscles.

Subscapularis

Greis et al and Kelly et al found that the activity on EMG of the subscapularis muscle is maximal and best isolated from the other shoulder internal rotators by the Gerber lift-off test. This muscle test is performed by raising thedorsum of the hand off the midlumbar area by maintaining or increasing internal rotation of the humerus and increasing extension of the shoulder. The ability to lift the dorsum of the hand actively off the back constitutes a normal lift-off test result. This test can be performed only if the patient has

adequate internal range of motion and the position is not painful. An alternative to the lift-off test is the belly-press test. This test is performed by pressing the palm into the abdomen by internally rotating the shoulder while keeping the elbow in the frontal plane .A positive sign for weakness is when the patient compensates to maintain pressure against the abdomen by dropping the elbow behind the trunk and

extending the shoulder, rather than internally rotating the shoulder. Both the belly-press and lift-off tests activate the upper and lower subscapularis more than all other internal rotator musclesThe belly-press activates the upper subscapularis muscle significantly more than the lift-off test, whereas the lift-off test produces greater activity in the lower subscapularis. The shoulder internal rotators should be tested with the shoulder at 90 of abduction for patients unable to assume the Gerber lift-off test position. With this test, a high level of subscapularis muscle activity still occurs, coupled with increased activity in the pectoralis major and latissimus dorsi muscles, compared with the lift-off test.

Deltoid

Kendall et al  described testing for the anterior and posterior deltoid with the patient in the sitting position. The anterior deltoid muscle is tested with the shoulder abducted in the plane of the scapula to 90 and with the humerus in slight lateral rotation. The posterior deltoid muscle is tested with the shoulder in abduction to 90 with slight horizontal abduction and medial rotation. By analysis on EMG, Brandell and Wilkinson found Kendall’s tests for the anterior and middle deltoid muscles to be quite selective. Reinold et al demonstrated significantly greater middle deltoid activity in the empty can position and greater posterior deltoid activity in the prone full can position described by Blackburn et al. Horizontal abduction of the shoulder with external rotation also elicits high levels of muscle activity in both the middle and posterior deltoid muscles. Shoulder hypertension (hyperextension, not hypertension) isolates the posterior deltoid from the anterior and middle deltoid muscles, but not from the latissimus dorsi muscle. These positions may also be considered for testing deltoid strength.

Pectoralis Major

For the sternocostal part, the arm is brought toward the opposite hip, and for the clavicular part, the arm is taken toward the nose as resistance is isometrically applied.

Latissimus Dorsi, Teres Major, and Posterior Deltoid

The latissimus dorsi, teres major, and posterior deltoid muscles can be tested as a unit using a generic shoulder extension test. The shoulder is extended with full internal rotation.

Upper Trapezius

The upper trapezius muscle can be tested with the shoulder shrug muscle test. Ekstrom et al  found the

greatest activity in the upper trapezius with a slight modification of this test. These investigators added abduction

Middle Trapezius

The middle trapezius muscle can be tested with horizontal abduction with the shoulder in lateral rotation. Analysis on EMG demonstrated that this test produces not only maximum activity in the middle trapezius muscle, but also high levels of activity in the upper and lower trapezius muscles. Therefore, this test allows all parts of the trapezius muscle to be tested as a unit.

Lower Trapezius

Maximum activation of the lower trapezius muscle is achieved through a muscle test with the arm raised overhead in line with the lower trapezius muscle fibers. This test also produces high levels of activity on EMG in the upper and middle trapezius muscles. Therefore, it is another method that can be used for testing all parts of the trapezius muscle.

Serratus Anterior

Kendall et al  recommended the muscle test  for testing the serratus anterior muscle. Ekstrom et al  demonstrated significantly more activity on EMG in the serratus anterior muscle when it was tested in this

position as compared with a supine-scapular protraction test. In this test, the shoulder is flexed or abducted in the plane of the scapula to 125. The scapula is upwardly rotated as a result of this position, and the examiner tries to derotate the scapula by applying simultaneous pressure downward on the

arm and at the inferior angle of the scapula.

Rhomboid Major and Minor

The recommended test for the rhomboid major and minor Muscles. No evidence on EMG

exists to verify whether this is the optimal test. In this test, the examiner tries to derotate the scapula from a downwardly rotated position.

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