Inspiratory Muscle Training vs Slow Breathing: Two Very Different Breathing Methods

Inspiratory muscle strength training (IMST) and slow breathing both involve your breath, but they are almost opposites. IMST is short and effortful, like lifting weights with your breathing muscles. Slow breathing is long and gentle, a steady pace near 6 breaths a minute.

This article explains each method, what the key studies found, how they might work, and why IMST needs a conversation with your clinician first.

What is the difference between IMST and slow breathing?

IMST uses a small handheld device with an adjustable valve. You breathe in forcefully against resistance, which works the diaphragm and other breathing muscles. In the main blood pressure trial, people did 30 breaths a day, 6 days a week, at high resistance (Craighead et al., 2021). A session takes about 5 minutes.

Slow breathing needs no equipment. You breathe in and out gently at about 6 breaths a minute, for 10 to 15 minutes, most days. The trials pooled in a 2019 meta-analysis used 10 breaths a minute or slower for at least 5 minutes, at least 3 days a week, for at least 4 weeks (Chaddha et al., 2019).

What the IMST trial found

In a double-blind randomized trial, 36 adults aged 50 to 79 with systolic pressure of 120 mmHg or higher did either high-resistance IMST (75% of their maximum breathing-in strength) or a sham version at low resistance (15%), for 6 weeks. In the IMST group, casual systolic pressure fell from about 135 to 126 mmHg, and about 75% of that drop was still present 6 weeks after training stopped. The sham group saw no change. Blood vessel function, measured as how well an artery widens, improved by about 45% (Craighead et al., 2021). About 95% of sessions were completed.

That is a promising result. It is also one small trial, in fairly healthy adults, run by one research group. It needs larger confirmation.

How each might work

The two methods seem to act through different routes. IMST appeared to improve the lining of blood vessels: in lab tests, cells exposed to participants' blood after training made more nitric oxide, a molecule that helps vessels relax (Craighead et al., 2021).

Slow breathing seems to act through the nervous system. At 6 breaths a minute, the baroreflex, the body's automatic pressure-steadying loop, becomes more sensitive during practice (Joseph et al., 2005).

How to start safely

1. Talk to your clinician before IMST. It involves forceful effort and a device, so get a go-ahead first.
2. If cleared, use a proper training device. Settings should be built up gradually, ideally with guidance.
3. For slow breathing, sit upright with back support. Breathe in for 5 seconds and out for 5 seconds.
4. Practice slow breathing for 10 minutes a day. At least 5 days a week, for 4 weeks or more.
5. Do not mix the two in one breath. IMST is effortful; slow breathing should feel easy.
6. Keep a standard home blood pressure log. Measure at rest, not right after either practice.

Beginner fallback for slow breathing: 4 in, 4 out, for 5 minutes.

What an IMST session looks like

It may help to picture how different the two practices feel. In the trial, an IMST session was 30 inhalations against a valve set to a high level of resistance, done in a few sets with short rests (Craighead et al., 2021). Each breath in takes real effort, a bit like sucking a thick milkshake through a narrow straw, followed by a relaxed breath out. The whole thing takes about 5 minutes. It is tiring for the breathing muscles, which is the point.

A slow breathing session is the opposite: 10 to 15 minutes of gentle, easy breaths at about 6 a minute. It should feel calming, not effortful.

Because IMST involves strong pressure changes in the chest, it is the kind of practice where a clinician's input matters. The trial enrolled fairly healthy midlife and older adults and carefully set the resistance for each person.

Questions to ask your clinician about IMST

• Is high-resistance inspiratory training safe with my heart, lung and blood pressure history?
• Which device should I use, and who can help me set the resistance?
• How should I build up the resistance over the first weeks?
• Should I keep doing slow breathing as well, or focus on one?
• How should I track whether it is helping?

Can you do both?

There is no evidence on combining the two, but they do not obviously conflict. Some people may like a short IMST set for training and a separate slow breathing session for calm. If your clinician agrees, keep them at different times of day and measure your blood pressure at your usual times, rested, not right after either one.

What the research shows

• 36 adults, 6 weeks of IMST versus sham: systolic about 135 to 126 mmHg with IMST, mostly sustained 6 weeks later; no change with sham (Craighead et al., 2021).
• 17 trials of slow breathing: systolic about 5.62 mmHg below controls, high variation (Chaddha et al., 2019).
• 20 people with hypertension, lab: 6 breaths a minute raised baroreflex sensitivity (Joseph et al., 2005).
• 270 exercise trials: isometric exercise showed the largest average drop, about 8.24 mmHg systolic, with aerobic about 4.49 mmHg (Edwards et al., 2023).

The takeaway: IMST is a promising newer method with one small strong trial; slow breathing has more trials but a smaller, more variable average effect. Neither replaces medical care, and both sit beside better-established exercise.

Common mistakes

• Trying to "do IMST" by gasping in hard without a device. That is not what was tested and can cause dizziness.
• Starting at high resistance. Build up with guidance.
• Assuming one trial settles the question. It is early evidence.
• Measuring blood pressure right after training. Rest first.

Who should be careful

• Anyone on blood pressure medication: never stop or change medication without your clinician, and stand up slowly after practice.
• People with heart, lung or kidney conditions: check with a provider before either method, and especially before IMST.
• People with ear problems, a history of collapsed lung or recent surgery: forceful breathing against resistance may not be suitable; ask first.
• Anyone who is pregnant: discuss any new breathing training with your provider.
• Anyone who feels dizzy, faint or unwell: stop and breathe normally.