Asthma is a chronic respiratory condition characterized by inflammation and narrowing of the airways, making breathing difficult. While primarily affecting the lungs, asthma’s effects extend to the muscular system. Increased breathing effort during an asthma episode strains various muscle groups. This challenge can lead to immediate and long-term muscular consequences, affecting function, strength, and endurance. This broader impact on the muscular system is a significant aspect of living with asthma.
Respiratory Muscle Overload
During an asthma exacerbation, airways constrict due to inflammation, bronchoconstriction, and increased mucus, increasing airflow resistance. This forces primary respiratory muscles, like the diaphragm and intercostals, to work harder to move air. The increased effort for inhalation and exhalation places these muscles under stress. This increased exertion is often called an increased “work of breathing.”
When primary respiratory muscles are insufficient, accessory respiratory muscles are recruited to assist breathing. These muscles, not typically used in relaxed breathing, include those in the neck (sternocleidomastoid and scalene), shoulders, and abdomen. Their involvement helps lift the rib cage and expand the chest during inhalation, and sometimes compress the abdomen to aid exhalation. Sustained contraction of these muscles during an asthma attack can lead to soreness and stiffness, similar to post-workout fatigue, due to microscopic tears.
Chronic Muscular Strain and Fatigue
Repeated episodes of heightened respiratory effort can lead to long-term consequences for breathing muscles. Increased workload on the diaphragm and accessory muscles causes chronic fatigue. This sustained strain impairs their ability to contract efficiently, leading to altered breathing patterns. Some individuals with chronic asthma may develop a more shallow and rapid breathing pattern, less efficient than diaphragmatic breathing.
The burden on respiratory muscles diminishes their endurance, making everyday activities challenging. Studies indicate diaphragm dysfunction is prevalent in individuals with asthma, often linked to disease severity and duration. This chronic muscular fatigue contributes to breathlessness or reduced exercise tolerance, even between attacks. Impaired function of these muscles limits physical activity and overall quality of life.
Wider Muscular System Impacts
Asthma’s impact extends beyond respiratory muscles to affect general skeletal muscles. Chronic inflammation and nutritional status contribute to progressive loss of skeletal muscle mass. This systemic effect leads to overall muscle weakness and reduced physical function, impacting daily activities.
Certain asthma medications, particularly oral corticosteroids, contribute to wider muscular impacts. These medications reduce airway inflammation but can cause muscle side effects, leading to corticosteroid-induced myopathy. This involves muscle weakness and wasting, often affecting proximal limb muscles (e.g., hips and shoulders) and respiratory muscles. They decrease protein synthesis and increase protein breakdown, leading to atrophy. Its extent varies, but it is a recognized side effect, especially with prolonged or high-dose oral corticosteroids; recovery can take months after tapering.
Asthma symptoms, like breathlessness or fear of exacerbation during exertion, often reduce physical activity. This inactivity leads to deconditioning and loss of muscle mass and strength. Low muscle mass is common in moderate to severe asthma, linked to poorer lung function, reduced exercise capacity, and diminished quality of life. This creates a cycle: symptoms lead to inactivity, causing deconditioning, which exacerbates perceived breathing effort and limits well-being.