Tickling your ears with a pain-relieving Tens machine can improve heart health, a study has shown.
Applying electrical stimulation to the tragus - the small triangular flap at the front of the ear - helped the heart adjust its beating rate and prevented it being driven too hard.
Tens (transcutaneous electrical nerve stimulation) is a method of blocking pain signals to the brain by applying small shocks to the skin.
The battery-powered machines are commonly used to relieve chronic back pain or early labour pains.
Researchers conducting the new study applied Tens stimulation to the ears of 34 healthy volunteers for 15 minutes at a time.
Neuroscientist Professor Jim Deuchars, from the University of Leeds, said: "You feel a bit of a tickling sensation in your ear when the Tens machine is on, but it is painless. It is early days - so far we have been testing this on healthy subjects - but we think it does have potential to improve the health of the heart and might even become part of the treatment for heart failure."
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The technique works by stimulating a major nerve called the vagus which plays an important role in regulating vital organs including the heart.
A sensory branch of the vagus nerve extends to the outer ear. By sending electrical signals through the ear to the brain, the scientists were able to influence the nerve messages that influence heart beat.
Vagal stimulation has previously been used to treat a number of conditions, including epilepsy.
The research is published in the journal Brain Stimulation.
Dr Jennifer Clancy, who led the University of Leeds team, said: "The first positive effect we observed was increased variability in subjects' heartbeats.
"A healthy heart does not beat like a metronome. It is continually interacting with its environment - getting a little bit faster or a bit slower depending on the demands on it.
"An unhealthy heart is more like a machine constantly banging out the same beat. We found that when you stimulate this nerve you get about a 20% increase in heart rate variability."
Ear stimulation was also found to suppress the sympathetic nervous system, which drives heart activity via a different pathway using adrenaline.
"We measured the nerve activity directly and found that it reduced by about 50% when we stimulated the ear," said Dr Clancy. "This is important because if you have heart disease or heart failure, you tend to have increased sympathetic activity. This drives your heart to work hard, constricts your arteries and causes damage.
"A lot of treatments for heart failure try to stop that sympathetic activity - beta-blockers, for instance, block the action of the hormones that implement these signals. Using the Tens, we saw a reduction of the nervous activity itself."
Prof Deuchars added: "We now need to understand how big and how lasting the residual effect on the heart is and whether this can help patients with heart problems, probably alongside their usual treatments. The next stage will be to conduct a pre-clinical study in heart failure patients."