Building BIG forearms by training biceps
Reverse curls are the main exercise for forearm volume.
The biggest muscle ON the forearm is actually a bicep muscle and is used for elbow flexion. So reverse curl your forearms now and have your sleeves rolled up all winter lol.
You can use the thumbs or not. Keep the wrists flexed in a solid position and don’t come all the way up like a regular curl. Instead try to feel it in the target muscle – brachioradialis.
For fun do this exercise superset with regular under arm/suppinated curls.