See this video at t=34 secs: https://www.youtube.com/watch?v=yaK6TThRMdE&t=34s https://www.youtube.com/watch?v=yaK6TThRMdE&t=34s Seems pretty simple... I guess

See this video at t=34 secs: https://www.youtube.com/watch?v=yaK6TThRMdE&t=34s https://www.youtube.com/watch?v=yaK6TThRMdE&t=34s Seems pretty simple... I guess what is special is (1) you can do it while sitting, and (2) the muscle doesn't seem to get tired so you can do it all day.