I've read some (but obviously not all) of the recent literature on isometric exercises.
Isometrics are easy to perform but difficult to perform at appropriate levels.
Isometrics increase blood pressure more than any other form of exercise and can be damaging.
Isometrics increase strength through a very narrow window of range of motion. Unless you perform multi-position isometrics you will not equal a full range of motion exercise. In other words you will have muscles that look good, but don't necessarily work well.
I recall a guy doing isometric curls in the gym at maximal effort. About 5 minutes after he finished he had two black eyes from the blood pressure build up. Not good.
The current "best method" on isometrics is to work at 2/3 maximal effort 2 to 3 times per week, and one maximal effort weekly just to measure progress. Almost no one has access to the needed equipment to execute to the "best method".
I tested the isometrics by comparing my starting curl and my starting leg press before and after a 4 month period of isometric training. In both exercises my max lift went down over the 4 month period. We were using maximal isometrics at that time. Certainly it was the worst performance from any newly tried exercise regimen that I've tried.
And, no, I have never taken steroids.