LibAnswers

Article titles in AMA are all lowercase except for:

• The First Word
• Proper Nouns including names of techniques, methods, and tests
• Geographic Locations
• Official Acronyms: ACL, MRI

So a subtitle which usually follows a colon in the article title is not capitalized.  

For example:

Physical therapy students’ perception of their ability of clinical and clinical decision-making skills enhanced after simulation-based learning courses in the United States: a repeated measures design.

Didactic physician assistant students' perceptions of evidence-based medicine resources: a preliminary investigation.

In some instances, subtitles will not be separated by a colon and instead by a period or a question mark.  

For those that have a period between the title and subtitle, change the period to a colon

American physical therapy students in Great Britain. A special communication

Becomes

American physical therapy students in Great Britain: a special communication

For those with a question mark between the title and subtitle, leave the question mark and capitalize the subtitle as if the question mark is a colon

Strength in Differences? The Importance of Diversity to Students When Choosing a Physician Assistant Program

Becomes

Strength in differences? the importance of diversity to students when choosing a physician assistant program

Microsoft Word and Google Docs will try to capitalize the first word after the question mark, use the undo function to stop this from happening

If you need further help, contact a librarian