One of the first times I took an Applied Kinesiology class as a chiropractic student, I was amazed/dumbfounded/cynical at what I thought was a parlor trick, oral influence. One of the things you do is place a substance/vitamin in the mouth under the tongue and test a muscle or movement. If it improves, in theory your body "liked" the substance and there can be justification that your body needs it.
This past year I did some more work with AK and again came across this phenomenon. This time the whole class tested standing body rotation. Standing with the feet planted firm, arms straight out in front as if you're pointing a gun. You rotate as far as you can to the right and to the left without moving your feet. You keep doing this several times until your end range of motion (ROM) is achieved.
Then we tested 4 different products. Many people had no improvement. Many people responded to one or two. I was almost trying to will myself not to show improvement. In fact I would have preferred to show no improvement. I'm cynical. I put the substance under my tongue (not ingested) and immediately improved about 6 inches each way. Not only improved, the ease of motion with which I hit my end range was dramatically different.
I went searching for answers and there is some pretty remarkable research being done in the last few years. Most notably this study done with cyclists.
Carb sensing in the human mouth: effect on exercise performance and brain activity.
Essentially they took a carb solution and put it in cyclist mouth. They tested performance and it improved. They hooked them up to an MRI and saw what the brain did in response to having the carb solution in the mouth. Again, this was not ingested. The MRI showed certain parts of the brain light up with activity. They concluded that there are some unknown receptors around and under the tongue that are at this time unknown. Pretty awesome.
The product that I improved on was called Dynamic Greens. It for some reason helped my thoracic rotation. Will it help yours? I have know idea, but it continues to help me move just a bit easier. But, the old put this in your mouth and lets test your (fill in the blank) may have a little more validity then I used to give it credit for.