I've been doing power twister workout for the last 3 months and I noticed that I'm gaining strength, but no muscles (chest and arms). For the workout I’m using a 30kg power twister. I just bought a 60kg one, but I cannot bend it at all. Do you have any specific workout routine (using ONLY power twister) targeting chest, arms and a bit of the back?
I think it's quite natural you've gained strength and no muscle mass. You're getting more and more able to use the same muscles more efficiently. That's what isometrics do. They increase muscle fibres recruitment. That's what you've been doing.
I owe these infos to this wonderful guy that spoke about it in YouTube: https://youtu.be/RwHbWUXz98I