Most of us know that a slow stroke on the arm or back feels different from a quick rub. Researchers have found part of the reason: a set of nerve fibres in the skin that seem to be tuned to exactly that kind of touch.
A nerve fibre tuned to a caress
Most of what we know about touch comes from fast, insulated nerve fibres that tell the brain where and how you were touched. Hairy skin, which covers most of the body apart from the palms of the hands and soles of the feet, also has a second kind: low-threshold unmyelinated fibres called C-tactile afferents. Unmyelinated just means they lack the insulating coat.
In a 2009 study in Nature Neuroscience, researchers recorded from these fibres in volunteers while a soft brush was stroked across the skin at different speeds. The C-tactile fibres responded most strongly to speeds of about 1 to 10 centimetres a second, a slow, steady stroke. Those were also the speeds the volunteers rated as the most pleasant. The faster, insulated fibres did not show that pattern.
The authors described these fibres as a “privileged peripheral pathway for pleasant tactile stimulation” that probably signals friendly, close social contact.
More than a nice feeling
A 2017 study went further. Volunteers had a soft brush stroked across the forearm or the palm of the hand, either at 3 centimetres a second, which suits these fibres best, or at 30 centimetres a second. The slower stroking was rated as more pleasant and slowed the heart rate more, on both skin sites. Only the slow stroking on the forearm, where these fibres are found, also activated the muscle we use to smile, which the researchers measured with sensors on the face. They described this as the first evidence in people that this kind of touch carries a positive emotional value that can be measured without asking.
The results were not tidy. Ratings and heart rate did not differ between the forearm and the palm, so slow stroking seems to feel good on skin without these fibres too. The picture is more complicated than one nerve fibre explaining everything.
What this does and does not tell us about massage
These were laboratory studies using a soft brush on volunteers. They did not test massage, so they cannot tell us what happens during a treatment, or whether this is why some people feel calmer afterwards. A leading review from 2014 puts these fibres forward as the likely basis for the rewarding side of touch, which its authors present as a proposal.
In my treatments, long gliding strokes open and close the session. They are the nearest thing to the slow stroking used in these experiments, although the research did not test them.
What this means for you
- If slow, gentle touch feels good to you, that is a real response, and you do not need to justify it.
- You do not need firm pressure to enjoy a treatment. Choose the level that feels right.
- Massage is not a treatment for anxiety or low mood, whatever is happening in your nerves. If you are struggling, please talk to your GP.
For what trials of massage have found about stress and anxiety, see Massage and stress: what the research says.
Sources
- Löken LS and colleagues. Coding of pleasant touch by unmyelinated afferents in humans. Nature Neuroscience, 2009.
- McGlone F, Wessberg J, Olausson H. Discriminative and affective touch: sensing and feeling. Neuron, 2014.
- Pawling R and colleagues. C-tactile afferent stimulating touch carries a positive affective value. PLoS One, 2017.