With this trick your arms will be as light as a feather.
Go and stand in a (narrow) door-way and push your arms up against the door-posts for about 60 seconds. Push as hard as you can whole the time. After one minute quickly go to a place that provides enough space to move. Relax your arms while letting them hang down. If you did it all right, your arms will slowly rise up for no reason at all. Funny feeling :)