What causes muscle asthenia?

From the Guidelines

Muscle Asthenia Causes

Muscle asthenia is primarily caused by muscle metabolic dysfunction, which can result from various factors including impaired substrate delivery and utilization, and energy transformation issues within the skeletal muscle metabolic pathways 1. This condition can manifest as exercise intolerance, characterized by reduced peak oxygen consumption and increased lactic acid production.

Key Factors Contributing to Muscle Asthenia

• Mitochondrial oxygen consumption dysfunction: A common issue leading to muscle asthenia, often presenting with symptoms similar to those of abnormal oxygen transport conditions 1.
• Myopathic diseases: Conditions such as myotonic dystrophy type 1 can cause progressive muscle weakness, myotonia, and other systemic symptoms, contributing to muscle asthenia 1.
• Immunotherapy-related adverse events: Certain treatments, like immune checkpoint inhibitors, can lead to muscle symptoms, including pain, weakness, and fatigue, as part of their side effect profile 1.
• Statins and muscle symptoms: The use of statins can sometimes result in muscle symptoms such as pain, tenderness, stiffness, cramping, weakness, or fatigue, necessitating careful management and potentially alternative treatments 1.

Management and Prevention

While the management of muscle asthenia depends on the underlying cause, rest, hydration, and stretching can help alleviate symptoms in many cases. For conditions like myopathic diseases or immunotherapy-related adverse events, specific treatments targeting the underlying cause may be necessary. In the case of statin-induced muscle symptoms, adjusting the statin dose or switching to a different statin may be required 1. Maintaining a healthy lifestyle, including a balanced diet and regular exercise, is also crucial for preventing and managing muscle asthenia.

From the Research

Causes of Muscle Asthenia

Muscle asthenia, also known as muscle fatigue or weakness, can be caused by various factors. The following are some of the possible causes:

• Overtraining or overexertion, which can lead to muscle fatigue and weakness 2
• Undertraining or deconditioning, which can result in muscle weakness and fatigue 2
• Physical injury, which can cause muscle fatigue and weakness 2
• Muscle wasting mediated by aging, immobilization, or certain diseases such as arthritis, sepsis, or muscle dystrophies 2
• Systemic inflammation, which can lead to muscle fatigue and weakness 2
• Chronic kidney failure, which can cause muscle fatigue and weakness 2
• Muscle myopathies, which can result in muscle fatigue and weakness 2
• Multiple sclerosis, which can cause muscle fatigue and weakness 2
• Coronavirus disease 2019 (COVID-19), which can lead to muscle fatigue and weakness 2

Mechanisms of Muscle Fatigue

The mechanisms of muscle fatigue are complex and multifactorial. Some of the possible mechanisms include:

• Accumulation of metabolites within muscle fibers, such as lactate and hydrogen ions 3, 4
• Generation of an inadequate motor command in the motor cortex 3
• Failure of SR Ca2+ release by various mechanisms 4
• Effects of reactive oxygen species on muscle function 4
• Changes in muscle fiber composition, neuromuscular characteristics, and high energy metabolite stores 5
• Decreases in oxidative capacity, capillarization, and mitochondrial density 5

Effects of Physical Activity and Inactivity

Physical activity and inactivity can modify muscle fatigue. Acute or chronic increases in physical activity can result in structural, metabolic, hormonal, neural, and molecular adaptations that increase the level of force or power that can be sustained by a muscle 5. On the other hand, decreases in habitual activity level due to injury or sedentary lifestyle can result in partial or complete reversal of the adaptations due to previous training, manifested by reductions in fiber cross-sectional area, decreased oxidative capacity, and capillarization 5.