I've been getting into Sumo a lot recently and realised there's training concept they use that I really like and which would be good to get out into the wider martial arts world. They have a training concept called "chest lending" where a wrestler "lends" his chest for another wrestler to push against and train on. Like a form of resistance training. It's not (afaik) overtly competitive. Even wrestlers who are injured (withing reason) can lend their chest to help other wrestlers and so stay in training because it's not a full on training bout with risk of further injury. It's common for senior wrestlers to lend their chest to lower ranked wrestler to help them develop. It's sometimes used as a lower level rehab when coming back from injury. I've said in classes I've taught that the most important piece of training equipment in the gym/dojo/dojang/kwoon is the bodies of the other people you train with! And as you would any other piece of "training equipment" you should look after them. I like the idea that you "lend" your body to someone else and therefore should expect to get it back in the condition you gave it to them! I think this idea of chest/body "lending" should be more widespread in martial arts other than sumo. That got me to wondered about other ideas and concepts that people like that might be fairly niche or not as widely known as they should be?