A five-minute breathing exercise lowers blood pressure more effectively than a regular walk, research suggests.
A third of British adults have high blood pressure, raising their risk of heart attacks and strokes. Exercising regularly is known to ward off – and treat – high blood pressure, but just 63% of people over 16 in England are "physically active".
Initially prescribed for breathing disorders, so-called High-Resistance Inspiratory Muscle Strength Training (IMST) is increasingly being linked to improved outcomes for other health conditions.
IMST involves vigorously inhaling through a handheld device with resistance – like sucking through a tube that sucks back.
To test its hypertension potential, scientists from the University of Colorado Boulder analysed 36 adults with raised blood pressure. Half used IMST at a regimen of 30 inhalations a day for six weeks, while the remainder used a device with much lower resistance, acting as the control group.
The IMST group saw their blood pressure drop by up to nine points – equal to some hypertension drugs and even exceeding the benefits of walking for half-an-hour a day on five days a week.
Read more: Fasting lowers blood pressure in rats
Although it is unclear why strengthening the respiratory muscles lowers blood pressure, improved airway health may prompt cells to produce more nitric oxide, a molecule that relaxes arteries and wards off plaque build-up.
The Colorado scientists are now developing an app that enables people to do IMST at home with readily-available handheld devices.
"There are a lot of lifestyle strategies we know can help people maintain cardiovascular health as they age, but the reality is they take a lot of time and effort, and can be expensive and hard for some people to access,” said lead author Dr Daniel Craighead.
"IMST can be done in five minutes in your own home while you watch TV.
"It's easy to do, it doesn't take long and we think it has a lot of potential to help a lot of people."
Developed in the 1980s, half-an-hour of low-resistance IMST a day was initially used to strengthen the respiratory muscles of critically-ill patients.
The Colorado scientists have recently tested whether 30 inhalations a day at a higher resistance on six days a week may benefit a person's heart, brain and sports performance.
The 36 adults, aged 50 to 79, were healthy aside from having a systolic blood pressure of 120mmHg or higher.
Systolic blood pressure describes the force the heart pumps blood around the body. The ideal reading is between 90mmHg and 120mmHg, while 140mmHg or above is considered to be "high".
After six weeks of IMST, the participants' systolic blood pressure was reduced by an average of nine points – a benefit that remained for most after an additional six weeks.
"We found not only is it more time-efficient than traditional exercise programs, the benefits may be longer lasting," said Dr Craighead.
IMST's effect on diastolic blood pressure – resistance to blood flow in the vessels – was "modest", however, the "sham training" had no impact.
The results – published in the Journal of the American Heart Association – also reveal only IMST improved the ability of the participants' arteries to expand by 45%, with inflexible blood vessels being linked to hypertension.
These participants also experienced significant increases to their nitric oxide levels, as well as reduced markers of inflammation and "internal stress".
Watch: Phillips recalls breathing device over cancer concerns
"Remarkably", nearly all (95%) of the participants completed the experiment.
"We have identified a novel form of therapy that lowers blood pressure without giving people pharmacological compounds and with much higher adherence than aerobic exercise," said co-author Professor Doug Seals.
Previous research suggests postmenopausal women who are not taking oestrogen do not reap the benefits of exercise as much as their male counterparts.
In the Colorado study, however, the female participants did just as well as the males.
"If aerobic exercise won't improve this key measure of cardiovascular health for postmenopausal women, they need another lifestyle intervention that will – this could be it," said Dr Craighead.
IMST may also have potential when it comes to improving an athlete's performance.
"If you're running a marathon, your respiratory muscles get tired and begin to steal blood from your skeletal muscles," said Dr Craighead, who uses IMST as part of his marathon training.
"The idea is if you build up endurance of those respiratory muscles, that won't happen and your legs won’t get as fatigued."
The scientists have been granted $4m (£2.9m) to test IMST's potential over 12 weeks in 100 people who are following an exercise programme.
Experts from the Mayo Clinic have stressed people should check with their doctor before starting IMST.
Nevertheless, they added: "Taking a deep, resisted, breath offers a new and unconventional way to generate the benefits of exercise and physical activity."
Watch: Unconscious weightlifter forgot to breathe during 245kg deadlift