A common problem I see with athletes is having pain or difficulty getting into a chin up position, with a supinated (palm facing you) grip in full shoulder flexion. There are three common mobility limitations that might contribute to this. The below video will show an easy way to deal with forearm supination restriction.
Three Common Problems
1. Inability to complete forearm supination
2. Inability to complete shoulder flexion
3. Inability to complete shoulder rotation with flexion
The Fix: Pronator Teres Release
This video will teach you a simple soft tissue release move you can do yourself to address the inability to supinate the forearm. The muscle addressed in this video is the Pronator Teres.