I just saw this interesting post on shouting and performance, so thought I would take a closer look. The first reference (not included here as I don’t want to link to quackery) seemed OK until I scrolled down to the bottom of the pages. Where the about the author sections says he invented a machine that cures viral desease, cancer and other stuff. I instantly felt he had possibly rubbished any credibility with the eradicating cancer claim.
However the next bit of research they mention looks like it shows some effect in hand grip strength. Showing an increase in strength when a martial art breathe exercise similar to a grunt or shout is used.
So I would possibly forget the first reference but otherwise I quite liked this simple look at shout and how it polarises people opinions. You can read it here.