The scapular upward rotation is important for the upper limbs to function normally. If scapula do not perform their original function and do not conduct correct upward rotation, the scapula is out of the normal position, which may cause shoulder diseases such as shoulder impingement syndrome. If there is a structural problem in the scapula or a problem in the function of the surrounding muscles, an abnormal problem occurs in the position and movement of the scapula, resulting in an imbalanced muscle, which in turn causes dysfunction of the shoulder joint.
Rotator muscles of the shoulders are important muscles in maintaining the normal movement of the upper arm joint while raising the arm. Among the rotator muscles of the shoulder, the upper trapezius muscle rotates upward by pulling the scapula upwards and inwards when the humerus moves to raise the arm such as flexion or abduction. Along with this, the serratus anterior muscle helps keep the scapula attached to the chest when the humerus perform flexion, abduction, etc., and prevents the scapula from elevating and causes an upward rotation. The lower trapezius pulls the scapula downwards and inwards, helping to rotate upwards, while preventing the scapula from elevating excessively. These rotator muscles of the shoulder show abnormal muscle activity in various pathological conditions of the shoulder. People with shoulder impingement syndrome reported excessive contraction of the upper trapezius muscle when performing the arm raising motion compared to those who did not. At the same time, it was said that the muscles strength of the lower trapezius and serratus anterior muscles were weakened. 
Several methods were used to strengthen the rotator muscles of the shoulder. Among these, the scaption motion showed high muscle activity in all the muscles of the scapular upward rotation. However, excessive upper trapezius muscle activity has been reported to cause shoulder pain. Therefore, the protraction exercise was used to induce low muscle activity of the upper trapezius muscle and high muscle activity of the serratus anterior muscle. 
However, when performing this motion, the muscle activity of the serratus anterior muscle was significantly lower than that of other motions. In order to solve the above problems, the scapular upward rotation movement of the scapula was devised to significantly reduce the muscle activity of the upper trapezius muscle and increase the muscle activity of the serratus anterior muscle. However, there was no study comparing the muscle activity of the rotator muscles and their proportions during these exercises. To date, there have been no studies on muscle activity of the three muscles or the ratio of muscle activity to the muscles during scapula rotational resistance exercise. So, we wanted to find out what the difference in muscle activity of the three muscles is when performing scapular upward rotation, protraction, and scaption exercises. Then, we want to see if there is a difference in the ratio between the scapular rotator muscles.

Cohort/Group Label

Scapular upward rotation exercise group

Cohort/Group Description

Measurement of muscle activity during Scaption, Protraction, and Scapular upward rotation exercise by attaching electrodes to the skin surface of the upper, lower trapezius and serratus anterior muscles

Not collect nor Archive

Healthy adult men in their 20s to 30s in Wonju

simple random sampling

Gender

Age

Description

Healthy people in their 20s and 30s with no shoulder pain or abnormalities

Those under 18 years of age
Those who have continuous pain or surgical experience in the shoulder joint
Those with experience in shoulder dislocation or fracture
People with acute pain around the shoulder
People with pain or neurological problems on the shoulder

Muscle activities of upper trapezius, lower trapezius, serratus anterior

during scaption, protracion, scapular upward rotation exercise

Muscle activity ratio

after scaption, protracion, scapular upward rotation exercise