I was (still am) 100% skeptical about these things but yesterday I saw some at a tennis club for $30. I tried it out and they did 3 test. The same ones you see on you tube. 2 were basically me standing there and they tried to knock me down. Without the braclet, I tip over easy. With it, they couldn't get me down.
The third test, I just twist my body around as far as I could to test flexibiliy. I could turn much farther with the braclet.
I can't explain it. The only thing I can think of was they pull you down different with and without it but I couldn't tell how. But that doesn't explain the flexibility test.
Again I am still very sceptical. Its probably a placebo effect but I just can't wrap my head around the results of the test. My friend did it also and same results.