How stance works

 The effects of shoulder (or scapular) bracing on posture and scapular muscle activity.

Forward Head Round Shoulders Posture (FHRS) is commonly attributed to sitting at computers all day. A study found that subjects demonstrated an approximate 10% increase in forward head posture from their relaxed sitting postures when working with the computer display [link]. 

TLDR excerpt from paper above

"Based on the results of this research, companies have developed braces that patients can use to improve scapular position and muscle activity and treat shoulder conditions. These braces are designed to alter the posture of the shoulder and thoracic spine, causing favorable changes in scapular position, muscle activity, and movement . In studies of 15 healthy participants and 15 participants with scapular dyskinesis, Uhl et al, found that wearing 1 type of commercially available scapular brace increased posterior tipping, decreased upward rotation in the dominant and nondominant upper extremities, and decreased internal rotation during the lowering phase of elevation. They concluded, that the brace affected scapular position at rest and in the lower ranges of motion and might assist the scapular muscles in controlling scapular motion."

"Walther et al compared the effects of a functional brace with traditional rehabilitation and home-based programs in a group of participants with subacromial impingement syndrome. After 6 and 12 weeks, the braced group demonstrated the same improvements in shoulder pain and function as traditional rehabilitation groups. The authors concluded that bracing might be as effective as traditional methods for treating impingement syndrome. Thus, bracing might be a new tool to help correct scapular position and treat pain in individuals with shoulder conditions."


Further Reading: 

The effect of scapular posterior tilt exercise, pectoralis minor stretching, and shoulder brace on scapular alignment and muscles activity in subjects with round-shoulder posture,