I have been reading through this book on the matter: The Half Has Never Been Told: Slavery and the Making of American Capitalism by Edward E. Baptist https://www.goodreads.com/book/show/14894629-the-half-has-never-been-told

The descriptions of violence toward slaves is heavily discussed and is quite eye-opening to me, since this is not the version I was taught in school!

How can you tell? Just curious as a Marine veteran. We used to do jumping jacks and pushups in the gas room until the last man couldn’t take it anymore. Those were the days!

Edit: Oops nm, I found the source on this guy.

Absolutely it. Happened to me standing for a memorial service. Lots of stories from military where this happens, and “don’t lock your knees” is often taught first thing.