Here is a non-specific stretch that will target anything limiting the shoulder from extending. This may consist of soft tissue structures such the pec’s, anterior deltoid, or biceps OR the anterior gleno-humeral joint capsule and ligaments.
This is range of motion is particularly important in runners. If this range of motion is limited, runners may compensate by abducting their arms or swinging their arm around their body.
-First this compensation doesn’t look pretty.
-Second it is NOT energy efficient, and will bring on fatigue quicker.
-Third it may put the shoulder at risk of injury.
Make sure that shoulder extension range of motion is not what is limiting you from being able to run optimally.
The first stretch is done through going through my full range of shoulder extension actively.
The second stretch is much more aggressive as you can use your body weight to sink down and pull your shoulder into extension. To increase the demand of the stretch, bring the hands closer together on the pole/barbell.
Normal shoulder extension range of motion is shoulder to be between 45-60 degrees. However, it is important to not that the needed range of motion is specific for your particular activity. For example, you may need more than this to create large torque when participating in activities such as tennis or racquetball.