Testing sensation with a 256 cps tuning fork. To check sensitivity of the cutaneous nerves, you have the person lie face up on a table with their eyes closed while you tap a 256 cps tuning fork on the side of your knee and place the butt over the bottom of the heel. You then say: “Tell me if you feel vibration from the tuning fork or just pressure from the butt of the tuning fork without any vibration.” You repeat this test 3 times, and alternate whether or not you tap the tuning fork to produce vibration. If they are incorrect two out of three times, the test is positive as the person has impaired sensation. In an interesting study of different ways to identify balance deficits in people with low back nerve injuries, Frost et al. (60) demonstrate that the 256 cps vibration test is more accurate at identifying impaired balance than the more commonly used and expensive Semmes-Weinstein monofilament tests. Apparently, cutaneous receptors are very sensitive to 256 cps vibration (61), explaining why this test so accurately identifies individuals with balance problems.