What's next, blood letting to release the "bad humors"? It's total crock of sh!t with no medical validity but I guess people will buy into anything if they think it can give them an edge.
https://www.yahoo.com/sports/news/mystery-solved-circular-bruises-on-swimmers-backs-021603210.html
https://www.yahoo.com/sports/news/mystery-solved-circular-bruises-on-swimmers-backs-021603210.html