The IMST group had their systolic blood pressure (the top number) drop nine points on average after six weeks. The drop is comparable to the effects of various blood pressure medication regimens. The IMST group kept the majority of their benefits six weeks after they stopped practicing IMST. Additionally, the group observed a 45% rise in vascular endothelial function-- the capacity of arteries to expand. (Photo credit: Lisa Marshall/CU Boulder Today)

New CU Boulder study reveals that working out for just five minutes a day using a technique known as "strength training for your breathing muscles" reduces blood pressure and improves several vascular health markers as well as, if not better than, aerobic exercise or medication.

The study, which was published in the Journal of the American Heart Association, provides the best evidence yet that the regimen known as High-Resistance Inspiratory Muscle Strength Training (IMST) could help aging adults avoid cardiovascular disease, which is the nation's leading killer.

In the United States alone, 65% of individuals over 50 have hypertension, which is abnormally high blood pressure, placing them at risk for a heart attack or stroke. However, only around 40% of people meet the required aerobic activity recommendations.

"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 Daniel Craighead, an assistant research professor in the Department of Integrative Physiology. "IMST can be done in five minutes in your own home while you watch TV."

IMST is a technique that was developed in the 1980s to help severely ill respiratory illness patients strengthen their diaphragm and other inspiratory (breathing) muscles by inhaling strongly via a hand-held device that offers resistance. Envision sucking through a tube that sucks back at you.

Doctors first suggested a 30-minute-per-day low-resistance program when recommending it for respiratory problems. Craighead and colleagues at the University of Arizona have been experimenting in recent years to see if a more time-efficient protocol––30 inhalations per day at high resistance, six days per week––could similarly enhance cardiovascular, cognitive, and athletic performance.

In the recent study, they enlisted 36 healthy people between the ages of 50 and 79 who had systolic blood pressure that was greater than usual (120 millimeters of mercury or higher). Half of the participants underwent High-Resistance IMST for six weeks, whereas the other half followed a placebo regimen with significantly lower resistance. Participants had no idea which group they were assigned to.

The IMST group had their systolic blood pressure (the top number) drop nine points on average after six weeks, a decrease that well exceeds that achieved by walking 30 minutes five days a week. This drop is similarly comparable to the effects of various blood pressure medication regimens. They kept the majority of their benefits six weeks after they stopped practicing IMST.

"We found not only is it more time-efficient than traditional exercise programs, the benefits may be longer lasting," Craighead said.

In addition, the therapy group observed a 45% rise in vascular endothelial function, or the capacity of arteries to expand when stimulated, as well as a substantial increase in nitric oxide levels, a chemical important for dilating arteries and reducing plaque development. Nitric oxide levels normally decrease as people become older. After six weeks of IMST, markers of inflammation and oxidative stress, which might increase the risk of heart attack, were dramatically reduced. Interestingly, individuals in the IMST group completed 95% of the sessions.

"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 senior author Doug Seals, a Distinguished Professor of Integrative Physiology. "That's noteworthy."

The study was published in the Journal of the American Heart Association on June 29th, 2021.

Results. We performed a double‐blind, randomized, sham‐controlled trial to investigate whether 6 weeks of IMST (30 breaths/day, 6 days/week) improves blood pressure, endothelial function, and arterial stiffness in midlife/older adults (aged 50–79 years) with systolic blood pressure ≥120 mm Hg, while also investigating potential mechanisms and long‐lasting effects. Thirty‐six participants completed high‐resistance IMST (75% maximal inspiratory pressure, n=18) or low‐resistance sham training (15% maximal inspiratory pressure, n=18). IMST was safe, well tolerated, and had excellent adherence (≈95% of training sessions completed). Casual systolic blood pressure decreased from 135±2 mm Hg to 126±3 mm Hg (P<0.01) with IMST, which was ≈75% sustained 6 weeks after IMST (P<0.01), whereas IMST modestly decreased casual diastolic blood pressure (79±2 mm Hg to 77±2 mm Hg, P=0.03); blood pressure was unaffected by sham training (all P>0.05). Twenty‐four hour systolic blood pressure was lower after IMST versus sham training (P=0.01). Brachial artery flow‐mediated dilation improved ≈45% with IMST (P<0.01) but was unchanged with sham training (P=0.73). Human umbilical vein endothelial cells cultured with subject serum sampled after versus before IMST exhibited increased NO bioavailability, greater endothelial NO synthase activation, and lower reactive oxygen species bioactivity (P<0.05). IMST decreased C‐reactive protein (P=0.05) and altered select circulating metabolites (targeted plasma metabolomics) associated with cardiovascular function. Neither IMST nor sham training influenced arterial stiffness (P>0.05).

Conclusions. Here, we demonstrate that in both midlife/older men and postmenopausal women with above‐normal SBP, high‐resistance IMST lowers casual SBP and DBP, and reductions in the former are largely maintained at least 6 weeks after cessation of training. In addition, IMST lowers 24‐hour SBP compared with sham training and improves vascular endothelial function, in part by increasing NO bioavailability via increased eNOS activation and reduced ROS production and oxidative stress. Finally, IMST was found to be safe, tolerable, and to promote excellent adherence. Our results provide support for high‐resistance IMST as a promising lifestyle intervention for improving cardiovascular function and possibly decreasing the risk of CVD and other clinical disorders, such as cognitive dysfunction and chronic kidney disease.

Source: Craighead DH, Heinbockel TC, Freeberg KA, Rossman MJ, Jackman RA, Jankowski LR, Hamilton MN, Ziemba BP, Reisz JA, D'Alessandro A, Brewster LM, DeSouza CA, You Z, Chonchol M, Bailey EF, Seals DR. Time-Efficient Inspiratory Muscle Strength Training Lowers Blood Pressure and Improves Endothelial Function, NO Bioavailability, and Oxidative Stress in Midlife/Older Adults With Above-Normal Blood Pressure. J Am Heart Assoc. 2021 Jun 29:e020980. doi: 10.1161/JAHA.121.020980. Epub ahead of print. PMID: 34184544.