Reported
What practitioners describe.
The periaqueductal gray, activated in the method, dampens pain; cold on the face and neck has a long folk history.
Honestly graded
What the evidence says.
Muzik 2018 on the PAG; anecdotal for headaches.
Protocol
How to practice for this.
Breath
Three to four rounds each morning, seated, on an empty stomach.
Cold
End the shower cold; progress by degrees.
Commitment
Thirty days. Track it. Notice.
Safety, plainlyNever practice breathing exercises in or near water.
Personal experience, not medical claimsReported benefits are personal experiences; consult a physician for any medical condition. Read the safety doctrine.