You have to go to the Critical Alignment Institute for a yoga class in an old (but pretty) school by the Oostelijk Havengebied. The high, light spaces, bamboo floors with underfloor heating(!) and interesting details will definitely give you a good feeling. The same goes for the alignment yoga classes, of course!
The cell service at the studio is bad, so check in before you go in!
And get access to 399 gyms and studios in Amsterdam with one sports membership.