I can’t speak to the benefits of Wim Hof breathing directly, but I definitely feel that exercise that required deep breathing (i.e. running, swimming) helped improve my stutter greatly. And I’m not talking about just 5-10 minutes. More like, at least an hour of continuous deep breathing. I think I threw this idea out once before, but is it possible to stutter while running? Maybe some people can try that out and report back. I don’t stutter enough anymore to test this out myself. Poor breathing is definitely not the only thing that induces stuttering, but improved breathing can definitely lead to less stuttering so focusing on it in my opinion is definitely worthwhile. As an aside, I’ve been taking cold showers for more than 15 years and highly recommend them. I’m familiar with Wim Hof and have tried the breathing, but never got into it, and feel that cold showers and cold exposure are enough to see great mental and health benefits.