Breathing takes care of itself in most workouts, but lifting, side stitches and asthma need a plan

Key takeaways

• In a 1985 McMaster University study, bodybuilders’ blood pressure peaked at an average of 320/250 during heavy leg presses, partly from straining against a held breath¹.
• Healthy, active adults in a 1995 study all reached a training-level effort breathing only through the nose, though they moved less air at their peak⁶.
• A 2025 review of 10 mouth-taping studies, all about sleep, found little benefit and warned of a suffocation risk for people with blocked noses⁷.
• About 1 in 5 runners gets a side stitch in a given race; a big meal in the hour or two before, or a concentrated sugary drink, makes one more likely⁹.
• Exercise narrows the airways of up to 20% of people without known asthma, says a 2013 guideline; a breathing test confirms it, and a pre-exercise inhaler and a warm-up of short surges are its main tools¹¹.

In 1985, researchers at McMaster University in Ontario placed a thin tube in an arm artery of five experienced bodybuilders¹. Then they recorded each man’s blood pressure continuously as he lifted heavy weights until he couldn’t finish another rep.

The numbers were startling. During double-leg presses, the group’s pressure peaked at an average of 320/250 mm Hg¹. One man passed 480/350¹. Even a one-arm curl averaged 255/190¹.

Part of that spike came from breathing. Pressure readings at the mouth showed the men straining against a closed throat, a move called the Valsalva maneuver, which drives blood pressure higher still¹.

Heavy lifting is one of the few times your breathing choices change what happens inside your body. Most of the time, your brain matches breath to effort on its own.

Still, questions keep coming up about noses, mouth tape, stitches and asthma. Here is what the research shows, plus a breathing guide for common activities.

Your breathing shifts gears as effort rises

When you speed up, you take deeper breaths and more of them. At first, breathing rises smoothly with effort. Then it reaches a turning point that exercise scientists call the ventilatory threshold, where breathing starts climbing faster.

You can feel this shift, which is why the talk test in our cardio guide works: at moderate effort you can talk but not sing. You don’t need to count breaths on a walk or a ride.

Nose breathing works at easy and moderate effort

The nose warms and moistens the air you breathe in, which the mouth does less well. That’s one reason a University of Western Australia team tested nose-only breathing in 1995⁶.

They studied 20 active adults, ages 18 to 55, with no nasal blockage. Breathing only through the nose cut the most air they could move by about three times as much, in percentage terms, as it cut their peak oxygen use⁶. Yet every one of them could still work hard enough to build fitness⁶.

Researchers at Bern University Hospital in Switzerland tested a more practical question in 2024. Their 57 volunteers, a mix of heart patients and healthy younger and older adults, cycled for five minutes at half their peak power, an effort near that first threshold⁵. Each rode once with a nose clip and once with tape over the mouth, in random order⁵.

Nose breathing slowed the breath in every group. Healthy older adults dropped from about 28 breaths a minute to about 22, and people with heart failure from 30 to 22⁵. Power output stayed the same, and the effort didn’t feel any harder⁵.

The body also needed less air to clear the same carbon dioxide. In the heart failure group, that efficiency measure improved by about 9%, close to the roughly 10% that earlier studies found in healthy people⁵. The authors reported no outside funding⁵.

But these were short, moderate tests in a lab. Some people struggle to breathe through the nose at high effort, and two of the 14 healthy older volunteers had to stop after three minutes because of a blocked nose⁵.

Evidence rating: promising but early. If nose breathing feels easy on a gentle run or ride, it’s a reasonable habit. Open your mouth whenever you need more air.

Mouth tape was tested for sleep, and the results were thin

Mouth taping spread on social media, with celebrity backers promising better sleep and fresher breath⁸. In May 2025, a team led by Dr. Brian Rotenberg at Western University in Ontario reviewed the research in the journal PLOS ONE⁷.

The team pooled what 10 studies, covering 213 patients in all, learned from sealing the lips at night with tape or a strap under the chin⁷. Just two hinted at a small gain, limited to some people with mild sleep apnea, and the others found none⁷.

The bigger worry was safety. Four studies warned that people who mouth-breathe because their noses are obstructed could struggle to get air at all⁷. Allergies, a crooked septum, swollen tonsils or long-running nasal and sinus problems can leave someone in that position⁷. So can a cold, according to HealthDay, which also notes the danger of choking if a taped sleeper vomits⁸.

The review had no outside funding⁷. Notice what it covered: sleep, not workouts. We found no trials of mouth tape as a training habit; in the Bern study, tape was a supervised, five-minute lab tool⁵. To practice nose breathing, keep your lips closed by choice, so you can open them the moment you need air.

On heavy lifts, brace briefly and breathe through the rest

The McMaster team returned to the question in 1992². When 11 men did heavy sets of 10 leg presses, their blood pressure peaked at an average of 343/235².

The rise in arterial pressure tracked the rise in pressure inside the chest². The researchers concluded that a brief breath-hold is unavoidable once a lift demands more than about 80% of maximum effort².

Breathing out still seems to make a difference. A 1999 Strength and Conditioning Journal column cites a 1995 study by Narloch and Brandstater of leg presses at 85% and 100% of maximum. As the column reports it, pressures reached about 311/284 with a held breath, versus about 198/175 when lifters slowly breathed out during the push³.

There is an upside to bracing. A held breath raises pressure in the belly, which the column says may ease the load on the spine’s disks during a maximum lift³. A 2019 review of 16 studies found belly pressure topped 200 mm Hg during squats and was lowest during the bench press⁴. The authors suggested bench presses and rows for beginners and people with high blood pressure⁴.

The column says people with high blood pressure, a past heart attack or stroke, a hernia or recent belly surgery, and older adults need close supervision when lifting³.

Practical rules:

• Breathe out through the hardest part of the lift, and in as you lower.
• On light sets, count your reps out loud. You can’t count while holding your breath³.
• Save a short brace for a single heavy rep, and only if you’re healthy and trained.
• Build up gradually before heavy squats and deadlifts⁴.

Side stitches are common, harmless and still a puzzle

That sharp pain under your ribs has a formal name: exercise-related transient abdominal pain. Australian researchers Darren Morton and Robin Callister reviewed the evidence on it in 2015⁹.

In a survey of 965 athletes, 61% had a stitch in the past year⁹. Swimmers (75%) and runners (69%) reported it most, cyclists least (32%)⁹. In a single race, about one runner in five gets one⁹.

Youth raises the odds. Stitches struck 77% of active people under 20 but only 40% of those past 40⁹. The jab usually sits in the middle or upper belly along the rib edge, and more often on the right⁹.

The usual explanation blames the diaphragm, the main breathing muscle, but lung function stays normal during a stitch⁹¹⁰. A cramp in the belly muscles doesn’t fit either, because their electrical activity isn’t raised at the sore spot⁹. Morton and Callister think irritation of the lining of the belly wall fits best, though that remains unproven⁹.

Prevention starts at the table. Give a large meal or a big drink at least 2 hours to settle before you exercise, and closer to 3 or 4 if stitches plague you⁹. Concentrated sugary drinks caused the most trouble in lab tests: 83% of people got pain after one, versus 70% in comparison trials⁹. During exercise, frequent small sips may sit better than big gulps⁹.

Mid-stitch, people try deep breaths, pressing on the spot, stretching or bending forward, mostly on anecdote; stopping worked best⁹. A 2015 Canadian review added that a full breath out, breathing out through pursed lips, or matching breaths to footsteps may help, on limited evidence¹⁰.

A stitch causes no lasting harm¹⁰. Pain that lingers after you stop, or keeps coming back, should be checked, since other causes need ruling out¹⁰.

Getting winded after exercise can be asthma

Exercise-induced bronchoconstriction (EIB) means your airways narrow because of exercise, whether or not you have asthma¹¹.

A 2013 guideline from the American Thoracic Society (ATS) estimated that it affects up to 20% of people with no asthma diagnosis¹¹. It’s common in some sports: about 30% of ice rink athletes and 11% to 29% of competitive swimmers, a pattern linked to chemicals in indoor pool air¹¹.

Hard breathing is the trigger. Pulling in lots of air chills and dries the lining of the airways, and the chemical alarm that follows makes them clamp down¹¹. The worst of it usually comes after the workout ends, and without treatment it can take 30 to 90 minutes to clear¹¹.

You might cough, wheeze, feel tight in the chest or run short of breath, but plenty of other problems feel the same¹¹. That’s why the ATS wants a lung test: you blow into a meter before and after exercise, and a drop in how much air you can push out in one second makes the diagnosis¹¹.

If you have EIB, the guideline’s top tools are¹¹:

• A quick-relief inhaler about 15 minutes before exercise, backed by a strong recommendation and high-quality evidence.
• A daily controller medicine if symptoms persist.
• A warm-up of intervals or mixed efforts, also strongly recommended. In some people, though not all, 10 to 15 minutes of moderately hard work protects for about 2 hours afterward.
• A mask or scarf that warms the air in cold weather, a weaker recommendation.

The guideline mentions nose breathing but doesn’t formally recommend it¹¹. Severe attacks are rare, but deaths have occurred¹¹. The guideline dates from 2013, so ask your clinician which inhaler and plan fit you now. Don’t swap a prescribed inhaler for a breathing technique; our article on a placebo inhaler study shows why feeling better and breathing better can differ.

Breathing trainers help a little, but “Altitude” masks don’t create altitude

Breathing trainers are handheld devices that make you inhale against resistance, a workout for your breathing muscles. In a 2012 Sports Medicine review of 46 studies, including a meta-analysis (a study that combines results) of 8 controlled trials, researchers led by Sabine Illi found this training improved endurance in healthy people¹². Gains were larger in less-fit people and in longer tests¹².

Training masks, marketed with altitude in their names, add resistance while you exercise. In a University of Wisconsin-La Crosse study, 24 adults did six weeks of hard cycling with or without a mask¹⁴. Both groups raised their aerobic fitness, by 16.5% and 13.5%, a gap too small to rule out chance¹⁴.

The red blood cell measures the team checked didn’t change¹⁴. The authors concluded the mask doesn’t simulate altitude and acts more like a breathing-muscle trainer¹⁴.

A 2021 trial in 23 recreational runners tested both tools¹³. Runners who added a separate breathing trainer to interval workouts cut their 5-kilometer times by 5.7% and raised breathing-muscle strength by 32%¹³. Runners who wore a mask during interval workouts improved 3.1%, about the same as interval training alone (2.6%)¹³. The study was small and had no placebo group¹³.

Evidence rating: breathing trainers for healthy people are promising but early. Altitude claims for masks: evidence says no. These studies tested healthy people, so with lung or heart disease, use a trainer only with your clinician’s guidance¹²¹³.

A breathing guide by activity

Breath sits at the center of many movement traditions, from yoga to tai chi. The research backs their gentlest lessons, a relaxed breath and a gradual warm-up, far more than most products sold as breathing upgrades.

This guide is our own, built on the studies above. Coming articles on breath awareness and breathing exercises cover practices done at rest.

Activity	How to breathe	Watch for
Walking	Whatever feels natural; nose breathing worked well at moderate effort in lab tests5	Breathless at rest or on light effort (see box)
Running	Nose on easy runs if comfortable; mouth when you need more air56	Stitches: skip big meals and sugary drinks 2 hours before9
Strength training	Breathe out through the hardest part; count light reps aloud23	Dizziness or a pounding head: rest and lighten the load
Cycling or skiing in cold air	Warm up 10–15 minutes with short surges; cover nose and mouth with a scarf or mask11	Cough or wheeze after stopping: ask about EIB11
Swimming	Breathe out steadily underwater so you only need to breathe in as you turn	Indoor pool air can trigger EIB in some swimmers11
Yoga, tai chi, qigong	Follow the slow breath of the practice without forcing long holds	Lightheadedness: return to normal breathing

How strong is the evidence?

Claim	Evidence level	What the research shows
Heavy lifts sharply raise blood pressure	Strong evidence	Direct artery measurements in lifters, repeated by the same lab12
Breathing out during the push lowers that spike	Promising but early	One comparison, known to us through a 1999 column3
A quick-relief inhaler before exercise prevents EIB	Strong evidence	ATS strong recommendation, high-quality evidence11
An interval warm-up reduces EIB for a while in many people	Strong evidence	ATS strong recommendation, moderate-quality evidence; the effect doesn’t occur in everyone11
Nose breathing makes moderate exercise more efficient	Promising but early	Small, short lab studies56
Avoiding large meals and sugary drinks prevents stitches	Promising but early	Surveys and small lab studies9
Breathing-muscle trainers improve endurance	Promising but early	Pooled small trials; bigger effects in less-fit people1213
Mouth taping improves sleep or workouts	Not enough evidence	10 small sleep studies, mostly no benefit, with suffocation warnings; no exercise trials found7
Training masks simulate altitude	Evidence says no	No change in blood counts; no edge over training alone1314

Questions readers ask

The bottom line

Your body handles breathing during most exercise on its own. Nose breathing is a reasonable choice at easy and moderate effort, but mouth tape has been studied only for sleep, with thin results and real risks for people with blocked noses.

The moments that need a plan are specific. Breathe out through the hard part of a lift, and eat and drink lightly before runs. If you cough, wheeze or feel tight after exercise, get tested, because an inhaler and a good warm-up work well. And treat breathing gadgets with the same skepticism you’d bring to any product.

Related reading

• Low fitness rivals smoking as a health risk, and cardio can change it
• Most adults skip strength training, though under an hour a week goes a long way
• Swimming is easy on your joints, and being a safe swimmer takes five skills
• A fake inhaler made asthma patients feel better while their lungs showed no change
• The symptoms that mean call 911 now

Sources

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2. MacDougall JD, McKelvie RS, Moroz DE, Sale DG, McCartney N, Buick F. “Factors Affecting Blood Pressure During Heavy Weight Lifting and Static Contractions.” Journal of Applied Physiology, 1992;73(4):1590–1597. paulogentil.com
3. Childs JD. “The Impact of the Valsalva Maneuver During Resistance Exercise.” Strength and Conditioning Journal, 1999;21(2):54–55. paulogentil.com
4. Blazek D, Stastny P, Maszczyk A, Krawczyk M, Matykiewicz P, Petr M. “Systematic Review of Intra-Abdominal and Intrathoracic Pressures Initiated by the Valsalva Manoeuvre During High-Intensity Resistance Exercises.” Biology of Sport, 2019;36(4):373–386. termedia.pl
5. Eser P, Calamai P, Kalberer A, et al. “Improved Exercise Ventilatory Efficiency With Nasal Compared to Oral Breathing in Cardiac Patients.” Frontiers in Physiology, 2024;15:1380562. frontiersin.org
6. Morton AR, King K, Papalia S, Goodman C, Turley KR, Wilmore JH. “Comparison of Maximal Oxygen Consumption With Oral and Nasal Breathing.” Australian Journal of Science and Medicine in Sport, 1995;27(3):51–55 (Western Sydney University record). researchers.westernsydney.edu.au
7. Scimex. “Social Media Fad of Nighttime Mouth Taping May Pose Serious Risks” (news release on Rotenberg B, et al., PLOS ONE, 2025, doi:10.1371/journal.pone.0323643). May 22, 2025. scimex.org
8. Thompson D. “Mouth Taping for Better Sleep? Little Benefit, Lots of Risk, Review Says.” HealthDay, May 22, 2025 (reprinted by Powers Health). powershealth.org
9. Morton D, Callister R. “Exercise-Related Transient Abdominal Pain (ETAP).” Sports Medicine, 2015;45(1):23–35 (Avondale University repository). research.avondale.edu.au
10. Shephard RJ. “The Endurance Athlete’s ‘Stitch’: Etiology and Management of Exercise-Related Transient Abdominal Pain.” Health & Fitness Journal of Canada, 2015;8(3). hfjc.library.ubc.ca
11. Parsons JP, Hallstrand TS, Mastronarde JG, et al. “An Official American Thoracic Society Clinical Practice Guideline: Exercise-Induced Bronchoconstriction.” American Journal of Respiratory and Critical Care Medicine, 2013;187(9):1016–1027. THORACIC.ORG
12. Illi SK, Held U, Frank I, Spengler CM. “Effect of Respiratory Muscle Training on Exercise Performance in Healthy Individuals: A Systematic Review and Meta-Analysis.” Sports Medicine, 2012;42(8):707–724 (ProQuest abstract). pubmed.ncbi.nlm.nih.gov
13. Faghy MA, Brown PI, Davis NM, et al. “A Flow Resistive Inspiratory Muscle Training Mask Worn During High-Intensity Interval Training Does Not Improve 5 km Running Time-Trial Performance.” European Journal of Applied Physiology, 2021;121:183–191. link.springer.com
14. Porcari JP, Probst L, Forrester K, et al. “Effect of Wearing the Elevation Training Mask on Aerobic Capacity, Lung Function, and Hematological Variables.” Journal of Sports Science and Medicine, 2016;15(2):379–386. jssm.org
15. Tsakirides C, Stavropoulos-Kalinoglou A. “Physiology Group Screening Process” (adapted from ACSM’s Guidelines for Exercise Testing and Prescription, 10th edition). Leeds Beckett University, July 2020. Www.Leedsbeckett.Ac.Uk