Aqui wrote:
I don't want to sound (too) stupid, but could you explain to me how armswings create connection and energy flow?
Is it by opening the joints or stretching the tendons...?
It's not a stupid question as there are many different ways to do arm swings. From a Tongbei perspective, it should be about using movement connected from the back and the spine, and not only let the arms relax. You must learn to initiate movement from muscles close to the spine. For example, you can see how he press his whole shoulder blade back as he raises his arm in the beginning. In the second exercise he stretches his whole arm forward from the scapula as he swings it. If you know what to look at, you will see it.