When looking at forearm stretches, the forearm itself is quite technical when it comes to all of the muscles. In order to deal with the movements of the elbow, wrist, and fingers, there are 19 muscles in the forearm.
The below is the muscles divided into an anterior compartment (flexors) and a posterior compartment (extensors), with the flexors having approximately twice the bulk and strength of the extensors.
Anterior (Flexors) Compartment
Posterior (Extensors) Compartment
Stretching helps maintain the flexibility of the flexors and extensors which is important in preventing overuse injuries such as tenosynovitis and tendinitis.