Yes, the diaphragm is a muscle. It is a dome-shaped skeletal muscle that sits at the base of your chest, separating the chest cavity from the abdomen. It is the main muscle you use to breathe.
That answer sounds simple, but the diaphragm is unusual in a few ways. Unlike the muscles in your arms and legs, you do not have to think about using it. It works automatically, all day and all night. Yet you can also control it when you want to — for example, when you take a deep breath or hold your breath underwater.
This article explains what the diaphragm is made of, how it works, what it does besides breathing, and what can go wrong when it is injured, weak, or irritated.
What Kind of Muscle Is the Diaphragm?
The diaphragm is a skeletal muscle, the same category of muscle as your biceps or quadriceps. Skeletal muscles attach to bone and are usually under conscious control. The diaphragm is the main exception to that rule: it is a skeletal muscle that your brainstem drives automatically, much like the heart muscle drives itself.
It is shaped like an upside-down bowl or dome. When you inhale, the muscle fibers contract and the dome flattens and moves downward. That downward movement increases the volume of the chest cavity, which lowers the pressure inside your lungs relative to the outside air. Air flows in to equalize the pressure. When the diaphragm relaxes, it returns to its dome shape, chest volume decreases, and air flows out.
This is basic pressure physics, and it is the reason the diaphragm does most of the work of quiet breathing. Other muscles — the intercostals between your ribs and the muscles of your neck and abdomen — assist during exercise, coughing, or when breathing is labored. But at rest, the diaphragm does the heavy lifting.
Where Is the Diaphragm Located and What Does It Attach To?
The diaphragm sits like a ceiling over your abdominal organs and a floor under your lungs and heart. It attaches to the lower ribs, the sternum (breastbone) in front, and the lumbar spine in back. These attachment points anchor the muscle so it can pull and flatten.
Three openings pass through the diaphragm, allowing structures to travel between the chest and abdomen:
- The aorta, the body’s main artery, passes through behind the muscle.
- The esophagus, the tube that carries food to your stomach, passes through a gap called the esophageal hiatus.
- The inferior vena cava, a large vein returning blood from the lower body, passes through as well.
The phrenic nerves, which come from the neck region of the spinal cord, control the diaphragm. This is why an injury to the upper spinal cord can paralyze the diaphragm and make a person dependent on a ventilator to breathe.
Is the Diaphragm a Voluntary or Involuntary Muscle?
It is both, which is what makes it so unusual. The diaphragm is under automatic control most of the time, driven by a cluster of neurons in the brainstem that generate a steady breathing rhythm. You do not decide to breathe while you sleep, and you do not forget to breathe while you are reading this.
At the same time, the diaphragm receives signals from the motor cortex, the part of the brain that controls voluntary movement. That is why you can take a slow, deep breath on purpose, sing a sustained note, or hold your breath. The two systems work together, and the voluntary system can override the automatic one for short periods.
This dual control is a key difference between the diaphragm and most other skeletal muscles. Your biceps do not keep working when you are asleep. Your diaphragm never stops.
What Does the Diaphragm Do Besides Breathing?
Breathing is its main job, but not its only one. The diaphragm also contributes to several other functions:
- Coughing and sneezing. A forceful cough requires the diaphragm to contract sharply against a closed airway, then release. This generates the burst of air that clears the airway.
- Speaking and singing. The diaphragm helps regulate airflow and pressure, which supports steady vocal output.
- Core stability. The diaphragm works with the abdominal muscles and pelvic floor to help stabilize the trunk during lifting and other effort.
- Vomiting and childbirth. Both involve coordinated pressure changes that the diaphragm helps produce.
- Urination and defecation. The diaphragm participates in the pressure shifts that support these processes.
The role in core stability is worth noting because it is often oversold in fitness marketing. The diaphragm does contribute to trunk pressure regulation, but claims that “diaphragmatic breathing” alone will fix back pain or dramatically improve athletic performance are not supported by strong clinical evidence. Some studies suggest breathing exercises can help with certain conditions, but results vary.
What Happens When the Diaphragm Is Weak or Damaged?
When the diaphragm is weakened or paralyzed, breathing becomes harder, and the body has to rely more on the accessory muscles in the neck, chest, and abdomen. This is less efficient and can lead to shortness of breath, especially during activity or when lying flat.
Common causes of diaphragm weakness include:
- Injury to the phrenic nerve or the upper spinal cord
- Neuromuscular conditions that affect muscle strength
- Complications from certain chest or abdominal surgeries
- Long-term lung disease that overworks the muscle
- Severe malnutrition or prolonged mechanical ventilation
Doctors can assess diaphragm function using imaging, breathing tests, and nerve studies. Treatment depends on the cause and may include breathing training, physical therapy, or, in serious cases, mechanical support. There is no single treatment that works for every cause.
What Is a Diaphragm Spasm or “Diaphragm Flutter”?
A diaphragm spasm is a sudden, involuntary contraction of the muscle. People often describe it as a fluttering or twitching feeling under the ribs. Hiccups are a well-known example: they happen when the diaphragm contracts sharply and the vocal cords snap shut, producing the characteristic sound.
Occasional spasms are common and usually harmless. They can be triggered by eating too quickly, drinking carbonated beverages, sudden temperature changes, or irritation of the nerve that controls the muscle. Persistent or painful spasms, or spasms that come with shortness of breath or chest pain, should be evaluated by a doctor, because other conditions can cause similar symptoms.
It is worth being clear about one thing: chest pain and shortness of breath have many possible causes, some of them serious. Do not assume a diaphragm problem is the explanation without medical assessment.
Does the Diaphragm Have a Role in Digestive Problems?
Yes, in a specific way. The esophagus passes through an opening in the diaphragm called the hiatus. When part of the stomach pushes up through that opening into the chest, the condition is called a hiatal hernia. Many people with a hiatal hernia have no symptoms. Others experience heartburn or acid reflux, because the barrier between the stomach and esophagus is disrupted.
Hiatal hernias are common, especially with age, and are usually diagnosed with imaging. Treatment ranges from lifestyle changes and acid-reducing medications to surgery in more serious cases. Not everyone with a hiatal hernia needs treatment.
Can You Strengthen the Diaphragm?
Yes, the diaphragm can be trained, though the evidence for how much this helps in healthy people is limited. Breathing exercises that emphasize slow, deep breaths are widely used in physical therapy and respiratory rehab. Some studies suggest they can improve breathing efficiency and reduce breathlessness in people with certain lung or heart conditions. Results in healthy athletes are less clear.
Devices that add resistance to breathing are also marketed for training the inspiratory muscles. Some research indicates these can improve inspiratory muscle strength, but whether that translates into better athletic performance is debated.
If you have a lung condition, heart condition, or recent surgery, talk to your doctor before starting any breathing exercise program. The right approach depends on your specific situation.
Frequently Asked Questions
Is the diaphragm a muscle or a membrane?
It is a muscle, specifically a skeletal muscle. The word “diaphragm” is also used for other thin barriers in the body, such as the pelvic diaphragm, which can cause confusion.
Can you live without a diaphragm?
No. The diaphragm is required for normal breathing. If it is paralyzed on both sides, a person usually needs mechanical ventilation or a diaphragm pacing device to survive.
Does everyone have a diaphragm?
Yes. The diaphragm is a normal part of human anatomy present in all people. Rare congenital conditions can affect how it forms, but the muscle itself is universal.
Is the diaphragm the strongest muscle in the body?
No. The diaphragm is essential and works continuously, but it is not the strongest muscle by force. The muscles of the jaw and legs generate more force per contraction.
