Understanding Chest Breathing 

During chest breathing, the intercostal muscles are primarily engaged, these are small muscle groups located between the ribs that help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping to expand and shrink the size of the chest cavity. When you inhale, the external intercostal muscles contract, creating a small vacuum that allows the upper lungs to fill with air. During quiet expiration, the external intercostal muscles relax, reducing the space in the chest cavity, which gently forces air out of the lungs. However, during forced expiration, the internal intercostal muscles also contract, actively forcing air out of the lungs (1). In sum, chest breathing, or thoracic breathing involves the expansion and compression of the chest and upper rib cage. 

This method primarily uses the intercostal muscles and is often characterized by shorter, shallower breaths. As such, upper-chest dominant breathing is associated with increased flow limitation, work of breathing, hyperventilation, and postural instability (2–4). 

Understanding Diaphragmatic Breathing

The diaphragm is a large, dome-shaped muscle located at the base of the lungs. Its primary function is to aid in respiration. When you inhale, the diaphragm contracts and flattens, creating a vacuum that allows the lungs to expand and fill with air. During exhalation, the diaphragm relaxes and returns to its dome shape, helping to expel air from the lungs (1,5,6). In sum, belly breathing, also known as diaphragmatic breathing, involves drawing air deep into the lungs by fully engaging the diaphragm. This technique contrasts with shallow chest breathing, where air only fills the upper lungs. 

Diaphragmatic breathing is foundational in most breathwork practices as it supports maximal air intake and offers numerous physical and psychological benefits (7). For example, it is correlated with various positive health benefits, including reduced resting heart rate, post-exercise oxidative stress, increased postural control, and baroreflex sensitivity (2,7,8). 

Why Diaphragmatic Breathing is Preferred 

1. Improved Oxygen Exchange: Belly breathing promotes more efficient oxygen exchange. When the diaphragm contracts, it creates more space in the chest cavity, allowing the lungs to expand fully. This deeper inhalation increases oxygen intake and enhances the removal of carbon dioxide from the bloodstream (9,10). 

2. Stress Reduction and Relaxation: Activating the diaphragm stimulates the parasympathetic nervous system, which induces a state of relaxation and counters the body’s stress response. Research indicates that belly breathing can lower cortisol levels, the hormone associated with stress, leading to reduced anxiety and enhanced calmness (10–13). 

3. Enhanced Lung Function: Practicing belly breathing can improve overall lung function. By engaging the diaphragm, individuals can enhance their lung capacity and respiratory efficiency (14). Studies have found that diaphragmatic breathing exercises significantly improve lung function in patients with chronic obstructive pulmonary disease (COPD) and asthma (15–18). 

4. Better Posture and Core Stability: Belly breathing encourages proper posture by engaging the core muscles, including the diaphragm, the transverse abdominal muscle, and the pelvic floor muscles. This engagement helps maintain spinal alignment and stability, which is crucial for overall musculoskeletal health. Improved core stability can also reduce the risk of back pain and injury (19). 

When to Use Belly Breathing

1. During Relaxation: Belly breathing is ideal for relaxation practices. Its ability to activate the parasympathetic nervous system makes it an effective tool for calming the mind and body. Practitioners often use belly breathing to achieve a calm state. 

2. In Stressful Situations: Incorporating belly breathing in stressful situations can help manage acute stress responses. Taking deep, diaphragmatic breaths can quickly reduce anxiety and promote a sense of control and relaxation. 

3. For Managing Respiratory Conditions: Individuals with respiratory conditions such as asthma or COPD can use belly breathing to improve breathing efficiency and reduce symptoms. It is a recommended technique in pulmonary rehabilitation programs to enhance respiratory function and overall quality of life. 

Summary

Belly breathing offers a range of benefits, from improved oxygen exchange and stress reduction to enhanced lung function and better posture during breathing exercises. This technique is versatile and can be used in various contexts, including relaxation, stress management, and to improve respiratory health. Understanding and practicing diaphragmatic breathing can significantly improve overall well-being.