I started with a teacher for the Alexander Technique (which this guy is definitely a student/teacher of) over this summer. At the beginning of almost all of my classes I would feel like it was a bunch of snake oil just because it seems too new age like for me. However within the first half of the classes my voice would always deepen, my chest would always expand and my back would always become more relaxed as the teacher guided me through the movements.
It's definitely helped with my posture but also helped me get better form in working out and martial arts. It's also deepened my voice enough that I'm having to retune my singing based off of my new register.
There's definitely some good ideas in that field.
"You can demonstrate the purpose and limits of human digestion with a simple experiment: eat a steak with some whole corn kernels, and see what comes out the other end. It won’t be the steak."