The pain was made worse because of the release of pain signals from certain immune cells in the spinal cord. (bigthink.com)
Experts say that it is also possible the application of pressure can somehow reduce the number of pain signals transmitted to the brain for interpretation. (mypetneedsthat.com)
Researchers aren't sure why it works on headaches, but suspect it helps to block pain signals in the brain. (canadianbusiness.com)