H-3 VISA
The H-3 Visa is specifically designed to enable workers in 'any field of endeavor' to train in the U.S. (USCIS). Although this loose classification includes agriculture, technology, communications, and governmental leadership, it does not apply to people seeking graduate medical training.
This visa can also be used by people entering the U.S. to receive training in special education 'of children with physical, mental, or emotional disabilities' (USCIS).
Your spouse and unmarried children under the age of 21 may join you in the U.S. under the H-4 status; however, these dependents are not permitted to work.
Documents
Along with the requisite application documents, the H-3 Visa requires your employer to provide the following:
Proof that this training is not available in your home country, and that this training will aid you in your career.
Proof that you will not engage in willful employment while in the U.S.
Proof that the training is formal in nature.