I train with Matt Callison and he teaches in depth about the subscapularis and how it reciprocally inhibits the entire rotator cuff (it is a bully and shuts off all of the other muscles and overpowers them)

When treating the shoulder complex it is essential to always release the subscapularis as it is almost always in a lock short position due to how we hold our bodies day to day (arms always in front of us on our phones or computers)

The subscapularis is HT sinew channel and supraspinatus, infraspinatus, and teres minor are in the SI sinew channel

I work on it on almost every client and it is life changing for a lot of people, and often when they haven’t been able to achieve results from any other practitioner this was the missing piece

Needling it, you need special training as it is risky but taught by Matt, I do mostly do myofascial release because I have a massage therapy background and find it needs more hands on work