Your ‘grunting’ sounds at the gym can tell you a lot about your breathing and strength – Muscle and Fitness

Walk into almost any commercial gym during peak hours and you’ll hear it: a sudden throaty growl that cuts through the hum of treadmills and clanking records. Sometimes it is accompanied by a heavy deadlift or chest press. Other times, a pec deck set that barely warrants a raised eyebrow, let alone a primal scream.

So when is it okay to growl, and is it fair that you get irritated when you hear others do it? According to James Nestor, New York Times bestseller author of Breath and one of the leading voices in modern respiratory science, the answer has less to do with gym etiquette and more to do with pressure, physiology and control.

“Grunting can only help if it’s an accidental byproduct of proper breathing,” Nestor explained Muscle & Fitness.

That distinction between accident and intention is perhaps the clearest boundary between performance breathing and what Nestor calls performative breathing.

The role of intra-abdominal pressure in heavy lifting

Central to the debate, Nestor explains, is intra-abdominal pressure. Heavy lifting requires a stable, pressurized torso that protects the spine and allows force to be transferred efficiently.

The diaphragm, an umbrella-shaped muscle under the lungs, plays a key role. When it contracts, it descends, the abdomen expands, and pressure builds around the torso like an inflated column. In layman’s terms, it is often called abdominal breathing.

“When this pressure is slowly released through the airways, a sound can occur, you might call a grunt,” Nestor explains. “Growling is not the goal, but rather the result of releasing pressure.”

He further noted that decades of sports science research into breath control during force production show that brief airway occlusion or resistance, including techniques similar to the Valsalva maneuver or controlled forceful exhalation, can increase maximal force output, often in the range of 2-10%, depending on the task. Improvements have been documented in measures such as grip strength, isometric strength and explosive power.

“This is not because the sound is loud, but because short-closing the airway (the glottis) increases pressure in the trunk, increasing the ability of the muscles to fire louder and more efficiently,” he notes, adding that when the growling becomes theatrical, something is breaking.

“The moment a growl becomes intentional, it’s usually a sign that the diaphragm is no longer engaged,” says Nestor. “Breathing shifts up into the neck, jaw and face, muscles that were never intended to stabilize heavy loads.”

Does growling increase strength and power?

One of the most persistent myths in gym culture is that louder breathing is a sign of more strength. According to Nestor, that is nonsense from a physiological point of view.

“There is no evidence whatsoever that increasing the volume of a grunt increases endurance,” says Nestor, noting that studies of breathing strategies during resistance exercises consistently show that coordination and timing are far more important than sound intensity.

He explains that a “functional grunt,” or a short, controlled, conscious cry, can be helpful, however. From a mechanical point of view, this is the body’s response to airway resistance. Constricting the vocal cords during exhalation increases resistance, maintaining lung inflation and trunk stability, similar to pursed lip breathing used in pulmonary rehabilitation. The effect is similar to air slowly leaking from a tire instead of pouring out all at once.

“The body doesn’t care about sound. It’s about controlling pressure,” says Nestor, adding that sound is just a byproduct. When sound arises from throat tension rather than controlled diaphragm engagement, the pressure dissipates quickly, which can result in less stability.

What happens if you gasp for air during a workout?

Another myth in the gym is that shortness of breath or gasping for air is a sign of a lack of oxygen. Not entirely, according to Nestor.

“You almost never run out of oxygen,” says Nestor. “What is killing performance is rising carbon dioxide.”

Rising CO₂ levels stimulate chemoreceptors that activate a distress signal in the brain to breathe, shifting the nervous system’s priority from performance to survival. Initially, your brain tells your body to stop focusing on lifting the weight and just breathe. According to Nestor, top athletes therefore train specifically to tolerate higher CO₂ levels.

“The more carbon dioxide your body can comfortably tolerate, the more oxygen you’ll get to your hungry cells, and the longer and stronger you’ll be able to perform,” he says, noting that many of the sounds you hear in the gym, such as forced exhalations, groans and grunts, are the result of the body reaching its limit of carbon dioxide tolerance and the brain taking an emergency break.

Therefore, grunting should support the lift and not show off. “If you grunt during warm-up, during each repetition or when there are people around, you have a problem, physically or psychologically,” Nestor emphasizes, adding that grunting due to pain can indicate poor load management and poor breathing mechanism.

How to breathe properly during heavy lifts

How you breathe should change based on your training program, the load you’re moving, and the physiological stress placed on your body. Here’s how Nestor breaks down how to breathe based on your workouts:

Maximum lifts: The priority is pressure and timing. Heavy loads require high internal pressure at the right time to keep the spine stabilized. This can happen through brief breath holding or through a ‘leaky’ exhalation that is timed and intentional.

Rep work, such as AMRAP: The main focus is to complete the greatest number of repetitions possible within a given time frame. This requires a consistent breathing pattern that remains organized and rhythmic while maintaining pressure without causing panic. Excessive breathing or dramatic breath holding will often reduce the number of sets you complete and limit overall volume.

Endurance and fitness: Priorities shift to efficient ventilation and the ability to tolerate carbon dioxide. He points out nasal breathing here, because it slows down your breathing and makes it more efficient. Additionally, it also promotes the release of nitric oxide, which allows your body to work longer and harder without breaking down.

Nestor underlines that studies have shown that when recreational athletes train with nasal breathing, they can achieve up to 85% of their maximum oxygen uptake (VO2max) during intense exercise.

“They can often achieve the same peak performance and oxygen consumption as when they used mouth breathing; however, they were breathing in about 20% less volume during that time,” he explains, adding that the same output with less effort means you can be stronger for longer. But there is a time and a place for everything. In upper Zone 4 and Zone 5 training, consciously switching to mouth breathing for short bursts can provide benefits.

When it’s okay to grunt at the gym

Before you roll your eyes the next time you hear someone at the gym grunt mid-set, it’s worth considering what that sound might represent. In some cases it reflects a controlled release of pressure during demanding exercise. In other cases, it indicates a disturbance in respiratory mechanics, load management, or nervous system regulation. Don’t be the last. The difference is important.

“The body doesn’t care how distorted your face is, or the timbre of your voice,” Nestor said. “It’s just about how to generate pressure efficiently, keep the nervous system stable and support all the body’s mechanisms.”