An active 24-year-old claims to have the slowest heart rate in the world.
Cameron Johnson's heart rate was recorded to drop to just 22 bpm (beats per minute), slower than that of elite athletes.
Currently, the world record belongs to a super-fit British retiree, whose 26 beats per minute was recorded during a check-up with his doctor.
Mr Johnson, an ecologist who lives in Newcastle, was first alerted to his ultra-low heart rate by a health tracker seven years ago. He also occasionally suffered from dizziness.
Speaking to MailOnline, Mr Johnson, a keen runner and cyclist, revealed he only recently got it 'fully checked'.
Cameron Johnson, 24, stays active despite his low heart rate and dizziness. He runs 5 km several times a week (photo), cycles, plays football and badminton
A cardiologist officially recorded his heart rate as being in the low 30s during an EKG a few years ago.
But the alarm bells only really went off in July when Mr Johnson's pulse was taken by his GP.
Shocked by the measurements, the doctor called an ambulance because they did not want him to drive home.
Mr Johnson said paramedics advised him to 'wear something to tell people that my heart rate is normally this low', in case he ever became unresponsive in the future.
After a few checks, the doctors said his abnormally low pulse is fine.
He told MailOnline: 'Doctors said it was fine.
“Sometimes I have a hard time believing it, but they say it's healthy and nothing to worry about.”
Mr Johnson's incredible speed of 22 beats per minute was recorded when doctors hooked him up to an ECG machine for 24 hours in September.
It showed that his average heart rate was 30 bmp, with dips to 22 bmp, including nighttime breaks.
Mr Johnson's incredible heart rate of 22 beats per minute was then recorded when doctors hooked him up to an ECG machine for 24 hours in September.
Normal heart rate ranges from 60 to 100 beats per minute, depending on activity level.
It varies depending on the activity, slowing down while people sleep and speeding up during exercise.
A low heart rate, usually lower than 60 beats per minute, can be a sign of a problem with the heart's electrical system.
This is medically known as bradycardia and can cause fainting and fatigue, which should be checked by a GP, according to the British Heart Foundation.
Heart block is a condition that causes the heart to beat more slowly or with an abnormal rhythm, the NHS says.
It is caused by a problem with the electrical pulses that control how your heart beats.
However, according to BHF, a slow heart rate can be normal for athletes.
For example, Sir Bradley Wiggins and Mo Farah recorded resting heart rates of 35 bpm and 33 bpm respectively.
It is estimated that more than 2 million Britons suffer from heart rhythm problems and most of them can lead normal lives, the BHF says.
“I was concerned about it because it's so rare,” Mr Johnson said.
'Most health warnings are about high heart rate and high blood pressure, but there isn't much about low heart rate.
'I was worried I would need a pacemaker, but the doctors said there was no point in giving me one at such a young age as it would cause more damage.'
To be officially recognized in the Guinness Book of World Records, Mr Johnson would have to be hooked up to an ECG machine for another 24 hours, but this time under the supervision of two Guinness representatives
Despite the dizziness, Mr Johnson says his heart rate is not preventing him from carrying out 'daily activities' as doctors have 'labelled it as healthy but worth monitoring'.
He continues to exercise several times a week, including two 5km runs, cycling and football and badminton.
Now Mr Johnson has set his sights on a place in the Guinness World Records for his ultra-low heart rate.
He said: 'I think I have pretty good reason to believe this is the lowest ever.
'It's quite rare in humans, but it's clearly more common in athletes.'
The current holder of the Guinness World Record is Martin Brady from Guernsey, who recorded a heart rate of 27 bpm in 2005 at the age of 45.
But pensioner Daniel Green received the same award from a separate jury in 2014 at the age of 81. He was found to have a resting rate of 36 bmp, which dropped to 26 bmp.
However, to be officially entered into the Guinness Book of World Records, Mr Johnson would have to remain hooked up to an ECG machine for another 24 hours, but this time under the supervision of two Guinness representatives.
They then took the lowest three measurements and used the average as the lowest heart rate number.
He should also be referenced in at least one published, peer-reviewed medical journal because he has a significantly lower heart rate than the norm for the rest of the population.
In addition, Mr. Johnson would require video evidence and various other forms, which he said would be a “big faff.”