I have used the isometric exercise known as ''The chair'', when you hold a squat position for a while now.

I have found exercises like this really, really hard, and you don't need very much time to make them very intense. I do them in all kinds of angles. From what I know exercises like these are often used for rehab purposes.

Now,
 

I wonder how usefull this exercise really is when it comes to protecting the body. Does strengthen the tendon and ligaments as effective (or maybe more) than plyometric exercises? Do PKG use it a lot? Anyone know what the Yamakasi guys think about it? Is it worth to keep on pushing through the extreme pain by doing exercises such as the chair?

NOTE;, I do a lot more exercises to avoid inuries aswell, but I'd just really wanted an answer about this one.