Why Do We Purse Our Lips? From Breathing to Body Language

Pursing your lips means pressing them together and pushing them slightly forward, creating a small, rounded opening. It is one of the most versatile movements your face can make, showing up in contexts from clinical breathing therapy to kissing to playing a brass instrument. The gesture relies on a single ring-shaped muscle that humans have refined over evolutionary time, and its medical applications alone span respiratory disease, blood pressure management, and exercise tolerance.

The Muscle That Makes It Possible

The orbicularis oris is a circular muscle that encircles the mouth, and it is the primary driver of lip pursing. Unlike most skeletal muscles, which connect bone to bone, the orbicularis oris is a sphincter: its fibers loop around the mouth opening, allowing the lips to close, protrude, round, and compress in different combinations depending on which fibers contract and how deeply they sit. Biomechanical modeling has shown that deeper fibers in the muscle’s periphery are best suited for protrusion and rounding, while more superficial fibers handle simple closure.¹ Jaw position matters too: protrusion and rounding work best when the jaw is relatively high, while closure can happen at various jaw heights.

What makes the human orbicularis oris unusual is how it differs from the same muscle in our closest relatives. Comparative anatomy of human and chimpanzee lip muscles shows that the upper fibers of the orbicularis oris have diverged to meet each species’ particular needs. In chimpanzees, the upper lip functions partly as a prehensile tool for grasping objects and food. In humans, those same fibers have adapted to support the fine motor control needed for speech and the wide range of facial expressions we use to communicate emotion.² Pursing your lips may feel like a trivial movement, but it sits on top of a muscle that has been reshaped by millions of years of evolutionary pressure toward speech and social signaling.

Pursed-Lip Breathing as a Clinical Technique

The most studied application of lip pursing is a breathing technique called pursed-lip breathing, or PLB. You inhale through the nose, then exhale slowly through lips that are pressed together with only a small gap between them, as if you were blowing out a candle at arm’s length. The exhalation typically takes about twice as long as the inhalation. Respiratory therapists have taught this technique for decades, and it remains a cornerstone of pulmonary rehabilitation for people with chronic obstructive pulmonary disease (COPD).

The mechanism is straightforward. In COPD, the small airways tend to collapse during exhalation, trapping stale air in the lungs. This trapped air is called dynamic hyperinflation, and it makes each new breath feel like trying to inhale into a balloon that is already half-full. Pursed-lip breathing creates a small amount of back-pressure during exhalation, which acts like a splint holding the airways open longer. A pilot study using dynamic CT imaging found that pursed-lip breathing significantly reduced airway collapse in patients with excessive dynamic airway collapse, and appeared more effective than some mechanical devices designed to do the same thing.³

Beyond keeping airways open, pursed-lip breathing changes the pattern of muscle recruitment during breathing. Research on respiratory muscle activity during PLB shows increased use of the rib cage and accessory muscles during both inhalation and exhalation, along with greater abdominal muscle recruitment on the exhale.⁴ The breathing rate drops, and the duty cycle of the inspiratory muscles shortens, giving them more rest between breaths. Interestingly, even healthy people experience some of these changes: a study of healthy subjects found that pursed-lip breathing increased expiratory resistance and promoted greater rib cage and abdominal muscle effort, though the inspiratory muscle pattern changed less than it does in people with lung disease.⁵

What Pursed-Lip Breathing Does for Oxygenation

One of the most consistent findings in research on PLB is a modest improvement in blood oxygen levels. In a study comparing COPD patients, healthy subjects, and a control group, the technique raised oxygen saturation by about 2% in the COPD group and about 1.7% in healthy subjects, with the improvement appearing during the breathing maneuver itself.⁶ A 2% jump may not sound dramatic, but for someone with COPD whose oxygen levels are already borderline, it can be the difference between comfort and distress.

Walking tests tell a similar story. When patients with moderate-to-severe COPD walked while spontaneously using pursed-lip breathing, their oxygen saturation dropped about 1.2% less than it did during walks without the technique.⁷ The effect is not huge, but it is reproducible and requires no equipment. For people who desaturate during daily activities like grocery shopping or climbing stairs, even a small buffer matters.

Exercise Tolerance and Breathlessness

Beyond oxygenation, PLB affects how far people can walk and how quickly they recover. A randomized crossover study found that in COPD patients with low peak expiratory flow, pursed-lip breathing reduced dynamic hyperinflation and improved exercise tolerance, breathing pattern, and arterial oxygenation during submaximal exercise.⁸ Another study measured respiratory rate and recovery time after walking, finding that PLB lowered the end-exercise breathing rate by about six breaths per minute and sped recovery from breathlessness by roughly 25 seconds.⁹

A 12-week breathing retraining program that focused on pursed-lip breathing showed significant reductions in perceived breathlessness after a six-minute walk, along with improvements in physical function, compared to baseline. Importantly, those benefits appeared only in the group trained in PLB and not in the control group.¹⁰ The combination of better oxygenation, slower breathing rate, and reduced hyperinflation all contribute to the overall effect on exercise capacity.

The picture is not universally rosy, though. One crossover study found that while PLB helped during daily living activities like sweeping and shelf-reaching, it did not improve hyperinflation during a standard six-minute walk test or improve performance on a multi-task functional test.¹¹ And the effect on perceived breathlessness during exercise varies from person to person. Research has shown that PLB can have a variable effect on dyspnea when performed deliberately during exercise, depending on how the technique changes each individual’s tidal volume and lung volume and whether their respiratory muscles can keep up with the demands.¹² Some COPD patients adopt pursed-lip breathing spontaneously, which tends to be a sign that the technique works well for them. For those who have never done it naturally, the benefits may be smaller or inconsistent.

Cardiovascular Effects

Pursed-lip breathing does not just affect the lungs. The slow, pressurized exhalation influences heart rate and blood pressure through pathways that connect breathing mechanics to the autonomic nervous system. A randomized controlled trial in patients presenting with dangerously high blood pressure found that pursed-lip breathing combined with number counting led to substantially greater drops in blood pressure compared to standard treatment alone. By the third hour, the intervention group’s systolic blood pressure had fallen by about 28 mmHg and diastolic by about 17 mmHg from baseline, with heart rate dropping by roughly 5 beats per minute. These reductions were significantly larger than those seen in the control group.¹³

The heart rate response to PLB has an interesting rhythm to it. Research in COPD patients found that heart rate rises during the inspiratory phase of pursed-lip breathing and falls during the long exhalation, with a swing of about 9 beats per minute between the peak and trough.¹⁴ That pattern reflects greater heart rate variability, which is generally a sign of healthy autonomic tone. However, the same study found no significant changes in blood pressure during PLB in the COPD patients studied, which suggests the blood-pressure effects may depend on the starting clinical situation. The dramatic drops seen in hypertensive urgency may not translate to someone whose blood pressure is already in a normal range.

When Pursed-Lip Breathing Falls Short

Pursed-lip breathing was developed for obstructive lung diseases, where airway collapse is the central problem. It does not work the same way in restrictive lung diseases, where the issue is stiff, scarred lung tissue rather than floppy airways. A crossover study in patients with interstitial lung disease found that acute PLB did not improve breathlessness, walking distance, or gas exchange, and was actually associated with higher metabolic demands than usual breathing. The researchers concluded that these results cast doubt on the technique’s usefulness in that population.¹⁵

That said, the broader picture of breathing exercises in interstitial lung disease is not entirely negative. A systematic review and meta-analysis found that breathing exercises as a category did improve lung function, breathlessness, exercise capacity, and quality of life in interstitial lung disease patients compared to controls.¹⁶ The catch is that “breathing exercises” is a broad category that includes diaphragmatic breathing, yoga-based breathing, and other techniques besides PLB. The evidence suggests that while the general principle of structured breathing helps in restrictive disease, PLB specifically may not be the right tool. This matters because people sometimes assume that a breathing technique helpful for one lung condition will transfer to another, and that is not always the case.

Lip Pursing in Infancy

The first thing most humans ever do with pursed lips has nothing to do with breathing exercises or communication. It is feeding. A newborn’s ability to seal its lips around the nipple or bottle is critical for generating the suction needed to extract milk. Biomechanical modeling of breastfeeding has shown that transforming the nipple into an elongated teat requires the infant to close its lips on the breast and maintain a subatmospheric pressure of about negative 20 mmHg throughout the feeding, with the cycling pressures during active suckling ranging between negative 20 and negative 40 mmHg.¹⁷ Without that lip seal, the vacuum cannot form and feeding fails.

Breast and bottle feeding actually produce different lip postures. Research comparing the two found that the angle of the mouth during breastfeeding is significantly larger than during bottle feeding, and there is a negative correlation between mouth angle and jaw movement.¹⁸ In other words, the wider mouth opening during breastfeeding goes hand-in-hand with a different jaw action. These differences in how the lips and jaw coordinate during early feeding are part of why speech therapists and pediatric dentists pay close attention to feeding mechanics: the orbicularis oris is getting its first workout, and the patterns established in infancy can influence oral motor development later on.

Evolutionary Roots of Lip Protruding

Pursing and protruding the lips appears to be an ancient primate behavior. Great apes regularly push their lips forward while grooming, feeding, and communicating. A recent review of the evolutionary origins of human kissing proposed that the familiar romantic kiss likely evolved from the final mouth-contact stage of grooming bouts in great apes, in which the groomer sucks with protruded lips on the fur or skin of the animal being groomed, latching onto debris or parasites.¹⁹ Over time, this functional behavior appears to have been repurposed into a social bonding and affiliative gesture.

The comparative anatomy of the orbicularis oris reinforces this story. As noted earlier, human upper lip fibers are adapted for speech and facial expression, while chimpanzee upper lip fibers remain suited for prehensile grasping.²⁰ The divergence suggests that the human lineage traded some of the raw gripping power of the lips for the fine motor precision that makes pursing, pouting, and the full range of labial speech sounds possible. Every time you purse your lips to whistle, blow a kiss, or pronounce a “p” or “b,” you are using musculature that is distinctly human in its wiring.

Lip Pursing in Music Performance

Brass and woodwind players rely on precise lip pursing for their livelihood. The lips act as a vibrating valve in brass instruments, and the degree of tension, the size of the aperture, and the force pressing the lips against the mouthpiece all determine pitch, tone quality, and volume. A study of trombone performance developed a novel measuring device to capture the forces exerted by the upper and lower lips against the mouthpiece under realistic playing conditions, finding that analyzing these lip-specific forces provides valuable insight into individual playing techniques.²¹ The researchers designed the device to minimally interfere with the musician’s natural posture, which underscores how sensitive brass playing is to even small changes in lip position.

Professional brass players often develop remarkable endurance and control in their orbicularis oris through years of practice, essentially giving that muscle an athletic training regimen. Fatigue in the lip muscles is one of the primary limiters of playing endurance, and the balance of force between the upper and lower lip shifts with range and dynamics. For players, pursed lips are not just a gesture but a finely calibrated instrument in themselves, and the subtle differences in how each player purses and presses against the mouthpiece contribute to the individual tone quality that distinguishes one trombonist or trumpeter from another.

Pursed Lips as Nonverbal Communication

Outside of medicine and music, lip pursing is one of the most universally recognized facial gestures. Tightly pressed, slightly protruded lips tend to signal disapproval, concentration, or that someone is holding back words they want to say. The expression is distinct from a pout, where the lower lip extends further and the overall posture conveys sadness or sulkiness. Pursed lips read as controlled restraint.

Context changes the meaning dramatically. A quick lip purse during a negotiation might communicate skepticism. The same movement while someone concentrates on threading a needle is just motor overflow, the face mirroring the fine motor focus of the hands. In some West African cultures, lip pointing, a directional pursing of the lips toward an object or person, functions as a conversational gesture equivalent to pointing with a finger, and is considered more polite. The underlying musculature is the same in every case; what differs is the social meaning layered on top.

The range of meanings humans load onto this one small movement speaks to a broader principle about facial expressions. The orbicularis oris did not evolve for communication alone. It evolved for feeding, for manipulating objects, for keeping airways pressurized. But because the face is the primary canvas for social signaling in primates, nearly every functional movement of the lips eventually acquired a communicative dimension. Pursing your lips is, in that sense, a muscle contraction that carries the full weight of human social life riding on a structure that started out just helping babies eat.