I discovered something interesting about doing isometric training using exercise bands: When you are holding against a challenging resistance, your muscles start to shudder a bit. This is quite noticeable because the bands start to vibrate. This interesting phenomenon is because your nervous system recruits muscle fibers to take the load. As fibers fatigue, and their strength “drops out”, others have to be recruited to replace them, which is not a totally smooth process. Eventually not enough can be recruited and you can’t hold the load.
I remember seeing this in strongman shows like “World’s Strongest Man” when they do static holds, their muscles noticeably shudder towards the end and you know they’ll soon lose their grip. Here is the great Mark Felix setting the world record for the Hercules hold:
And here is four time World’s Strongest Man Magnus Ver Magnusson doing the same event long after his retirement, at the age of 56!:
The video below shows your humble author (with somewhat smaller loads!). If you watch the bands as it zooms in (also the knuckles of my left hand) you can see the shuddering:
“Going for the shudder” is now good motivation for me. I try to hold for about 30 secs, and then keep going for a few seconds more while feeling a good shudder. I assume this is an indicator of working hard, but in any case it is fun.