Scapula kinematics of pull-up techniques

Scapula kinematics of pull-up techniques: avoiding impingement risk with training changes, by Prinold and Bull, in Journal of Science and Medicine in Sport (2015)

Background

Shoulder impingement syndrome (SIS) is often diagnosed by clinicians when an individual presents with pain (which is usually worse when the arm is positioned overhead), shoulder weakness, and a loss of shoulder range of motion (ROM). Sometimes, individuals also complain of popping sensations during some shoulder movements.

SIS is also referred to as subacromial impingement syndrome, and either swimmer’s or thrower’s shoulder. The underlying cause of shoulder impingement is believed to be compression of the rotator cuff tendons inside the subacromial space, which is the area beneath the acromion of the scapula.

Researchers and clinicians generally differentiate between two types of SIS: primary and secondary. It is thought that primary SIS is caused by compression of the rotator cuff tendons between the humeral head and the overlying anterior third of the acromion, coracoacromial ligament, coracoid or acromioclavicular joint, most likely following on from degenerative changes and spurring in the joint area. On the other hand, it has been suggested that secondary SIS can also lead to similar compressive symptoms following underlying instability of the glenohumeral joint or following scapular dysfunction.

Instability of the glenohumeral joint might feasibly arise where the shoulder is placed under excessive strain from powerful or repetitive overhead movements, such as are performed by swimmers and throwers, which might then lead to increased humeral head translation within the joint and consequently an impinged biceps tendon and rotator cuff.

Scapular dysfunction has been linked to a number of different shoulder disorders and may cause secondary SIS by increasing the contact between the greater tuberosity and posterior-superior glenoid and thereby impinging on the posterior rotator cuff tendons and labrum. Some researchers who have performed long-term trials of rehabilitation for SIS have provided details of their intervention programs. Others have made recommendations for exercises based on the results of acute investigations of muscle activity in individuals with and without SIS. Common exercise guide for the treatment of SIS includes:

• Strengthening of the middle trapezius, lower trapezius, serratus anterior and rotator cuff 
• Stretches for the upper trapezius and pectoralis minor, levator scapulae, latissimus dorsi and rhomboid

However, the exact exercise program that is optimal for SIS rehabilitation remains unclear.

Objective

To compare scapular kinematics (using a Scapular Tracker and a 9 camera motion analysis system tracking the position of 21 retro-reflective markers placed upon the upper body) and external forces (using a force plate upon which the pull-up frame was positioned) during three different pull-up techniques (pronated grip, supinated grip, pronated wide grip) performed for three repetitions per set.

POPULATION: 11 subjects, aged 26.8 ± 2.4 years who regularly performed pull-ups.

Results

The researchers observed significant differences in respect of scapula protraction-retraction between the three types of pull-ups. They found that the pronated, wide grip and supinated pull-ups displayed different protraction-retraction ROMs of 22, 10 and 17 degrees, respectively. Thus, the wide grip pulls up showed far less protraction-retraction ROM than the other two variations.

Conclusion

The researchers concluded that the wide grip pulls up display far less protraction-retraction ROM than the standard shoulder-width pull up variations (either pronated or supinated grips). They suggested that the wide grip pull up may therefore place individuals at greater risk of subacromial impingement.

Limitations

The study was limited in that it was an analysis of scapular biomechanics, which does not allow us to infer injury risk directly.