Yes, placebo effect is real. So is far infrared radiation.
Personally, I don’t believe these fabrics are any sort of miracle cure and certainly would not rely on them as a sole solution for a problem. But I have found the t-shirts, socks and wrist bands helpful for myself and I think the saddle pads and sheets might be helpful to the horses.
Call me a fool, but I also have a cold laser unit that I use occasionally on myself and the horses. People often poo-poo laser therapy, but CSU recommended I use it as a part of the rehab program for my horse’s suspensory injury. He also received the most advanced medical treatment available – mesenchymal stem cell therapy. They aren’t exactly sorcerers working in the dark ages there, so I am following their advice.
As for the magic sheets, this horse has become tight and stiff on extended stall rest and he needs a new stable sheet anyway, so I will probably try the Rambo and see if it helps. (I also give him beer and I am sure that it helps. :D)
My older horse has a kissing spine lesion and SI arthritis he is wearing a tattered old BOT sheet as part of his rehab program (which now includes physical therapy and chiropractic and will likely be followed up with injections).
Here are a couple of overviews on far infrared radiation with discussion on ceramic impregnated materials, including citations for a few double-blind studies.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3699878/
http://www.omicsonline.org/open-access/neurobiological-mechanisms-and-perspectives-on-farinfrared-emitting-ceramic-materials-for-pain-relief-2157-7595.1000159.pdf