ELI5 Cupping Therapy - can bruises really heal you?

Why do we see many professional athletes look like they were attacked by a giant octopus? How did a treatment from ancient history become the biggest trend in modern locker rooms? If a bruise is "stuck" blood, how can it actually help your blood flow? Can we really suck "bad energy" or "toxins" out of our muscles with a glass jar? Why do some doctors call this "quackery" while others say it's a powerful mental tool? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: breeze_in_the_trees, tateshinski, phage0070, doingthehumptydance, mohamed and zhang To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Twitter: https://www.twitter.com/eli5ThePodcast/ or send us an e-mail: [e-mail]